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REU Past Students

2017

  • Bridget Anger - Chemical Engineering, University of Maryland, Baltimore County
    Bridget AngerEducational Institution: University of Maryland, Baltimore County
    List of Mentors: Dr. Kane Jennings & Max Robinson
    Program: NSF REU
    Research Project: Efficient Charge Separation in Composite Photosystem I/PEDOT Photocathodes Prepared by Vapor Phase Polymerization 
    Poster: NSF REU Bridget Anger.pdf
    Research Abstract:   Photosystem I (PSI) is a stable, abundant, and highly efficient photocatalytic protein that is found in photosynthetic organisms and has been utilized in solar cells and hydrogen fuel cells. This project incorporates an electrically conductive polymer, poly (3,4-ethylenedioxythiophene) (PEDOT), in a PSI:PEDOT composite film, developed through vapor phase polymerization. Introducing conductive PEDOT into the film facilitates highly directional electron transfer when used in a solar cell with electrolyte solution. When a PSI:PEDOT composite film on a gold electrode is paired with a methyl viologen mediator and electrolyte solution, photocurrents of 1.35μA/cm2 have been recorded. In an effort to improve charge separation and increase photocurrent, we performed tests with anion exchange of ferri/ferrocyanide ions in the composite films, but the experimental data showed that films with anion exchange produced ~0.612 μA/cm2, which was less than half of the photocurrent recorded with films that had no anion exchange. While we had initially thought that cycling in the redox ions would make a more energetically favorable path for the electrons, we now believe that the incorporation of these ions decreases the charge transfer efficiency. Moving forward, we then developed a solar device composed of a dye-sensitized mesoporous TiO2 anode and a PSI:PEDOT composite photocathode which produced anodic photocurrents around 100 μA/cm2. When this device was tested with different concentrations of PSI and a control with only PEDOT, there was a strong correlation with higher concentrations of PSI resulting in higher photocurrent.
     
  • Mariah Arral - Chemical Engineering, University of New Hampshire

    Mariah ArralEducational Institution: University of New Hampshire
    List of Mentors: Dr. Scott Guelcher & Tom Spoonmore
    Program: NSF REU
    Research Project: Characterization ofS. AureusGrowth and ToleranceDevelopmentin 2D and 3D in vitroModels
    Poster: NSF REU Mariah Arral Poster.pdf
    Research Abstract:   Staphylococcus aureus  is a common bacteria that can infect fractures and cause serious bacterial infections. Chronic infections can be attributed to the presence of bacterial cell communities that are tolerant to clinically relevant treatment. These communities can be defined as biofilms and are relate to 80% of human infections. The goal of our experiments is to understand if and when tolerance develops to treatment of vancomycin and rifampin on 2D and 3D convex substrates in a novel  in vitro  biofilm model. Along with tolerance we will examine how  S. Aureus  strain UAMS-1 grows on 2D and 3D convex surfaces over time.   A second goal of our project is to characterize the ability of vancomycin and rifampin to eradicate infection when delivered through polyurethane foam carriers. From our experiments, we were able to conclude that regardless of seeding density and geometry bacterial cell communities grow to similar surface densities (LOG[CFU/cm 2 ]) after 24 hr. Vancomycin and rifampin tolerance studies proved that tolerant bacterial cell communities existed on the substrate surface following 24 hours of bacterial cell growth. We believe these tolerant cell communities to be biofilms based off the tolerant phenotype when exposed to vancomycin at concentrations up to 100 μg/mL. Interestingly, bacterial growth on 3D convex surface was found to have slower kinetic development of tolerance than bacterial infection on 2D surfaces, while the surface density of cells was determined to be similar. Finally, delivery of vancomycin and rifampin through polyurethane foams proved to inhibit bacterial growth on both the 2D substrate and the scaffold surface when delivered concurrently with inoculation. However, foams loaded with vancomycin or rifampin were unable to eradicate tolerant infections at 24 hours. Foams loaded with rifampin also became a nidus for infection when delivered to tolerant bacterial communities at 24 hours. Interestingly, foams loaded with 6 wt% vancomycin were able to inhibit the bacterial infection from spreading to the scaffold at 0, 6, and 24 hours, suggesting the ability to prevent biofilm cells from spreading to the scaffold surface. 

  • Timothy Bernard - Mechanical Engineering, University of Maryland, Baltimore County

    Timothy BernardEducational Institution: University of Maryland, Baltimore County
    List of Mentors: Dr. Leon Bellan & Brian O'Grady
    Program: NSF REU
    Research Project: Retrofitting a Commercial 3D Printer for Bioprinting Capabilities 
    Poster: NSF REU Timothy Bernard Poster.pdf
    Research Abstract:   In order to create Lower Critical Solution Temperature (LCST) polymer frameworks with complicated 3D structures, we present a low-cost hardware and software adaptation for a commercial dual extrusion 3D printer. The modified printer uses the two existing thermoplastic extruders and adds a third pressure extruder with a blunt needle to extrude biocompatible materials. In addition, the software revises the conventional G-Code instructions for the triple-extrusion process. This allows for three separate materials (including one biomaterial) to be printed on the same layer. 

  • Michael Davies - Physics/Mechanical Engineering, Fisk University

    Michael DaviesEducational Institution: Fisk University
    List of Mentors: Dr. Doug Adams & Cole Brubaker
    Program: NSF REU
    Research Project: Damage Detection In 3D Printed Parts Using Optical Properties of Gold Nanoparticles
    Poster: NSF REU Michael Davies Poster.pdf
    Research Abstract:   Gold nanoparticles (AuNPs) are a nanomaterial that possess unique optical properties that can be used in many applications as a sensing material. The Adams lab has developed another application for these AuNPs in the form of defect detection for 3D printed parts. AuNPs were synthesized and incorporated within polylactic acid (PLA) which was then 3D printed into various geometries (primarily a square and rectangular shape) with a varying number of print layers. These 3D structures were then tested to identify if the varying number of print layers had an impact on the absorbance of light of the materiel. It was determined that pure PLA (PLA without the AuNPs) saw no change in the absorbance of the material in the visible range regardless of the number of print layers. However, PLA with AuNPs showed a linear trend in absorbance based on the number of print layers in the 3D printed structure.  Using this trend, we were able to successfully identify and quantify the number of missing print layers and material defects in 3D printed structures based on the optical response of AuNPs alone.

  • Jenna Dombroski - Biomedical Engineering, SUNY College at Buffalo

    Jenna DombroskiEducational Institution: SUNY College
    List of Mentors: Dr. Qi Zhang & Kristina Kitko
    Program: NSF REU
    Research Project: Quantum dot-enabled tracking of single synaptic vesicle protein Synaptotagmin-1 in live neurons
    Poster: NSF REU Jenna Dombroski Poster.pdf
    Research Abstract:  Synaptotagmin-1 (Syt-1) is a prominent synaptic vesicle protein and one of the Ca2+ sensors that triggers neurotransmitter release. Given the heterogeneity of the synaptic vesicle population and the associated variation of Ca2+ sensors, it is informative to study the distribution and mobility of individual Syt1-containing vesicles within live neurons. Quantum dots (Qdots), a.k.a. photo-luminescent semiconductor nanocrystals, possess superior optical properties ideal for single vesicle tracking. Their high quantum efficiency leads to a large signal-to-noise ratio and their photostability enables long-term tracking. Qdots were randomly tagged to single vesicular Syt-1 in live neurons via a highly selective monoclonal antibody; stimulation-induced synaptic vesicle turnover. After labeling, continuous fluorescence imaging of single Qdots was performed while neurons were continuously stimulated to induce vesicle release. Image stacks were processed in FIJI and single Qdot tracking trajectories were generated using the TrackMate plug-in.

    We observed significant differences (>20%) between diffusion coefficients for stimulation vs. non-stimulation using antibody-conjugated Qdots. However, there was only a 6% difference in the mean diffusion coefficients between stimulation and another control - non-specifically uptaken Qdots. Looking further into this discrepancy, we noted that there was also a significant loss of Qdots over time during field stimulation (40%). Although the effect of activity is an important cornerstone of understanding vesicle mobility, results throughout the literature remain inconsistent. Given this information, we propose that a possible explanation for the discrepancies among the literature is that when vesicles release during field stimulation, Qdots are washed away after dissociating from the antibody in the acidic vesicular environment.  Future research directions involve combining Qdot imaging with dyes to specifically label synaptic vesicles, but this information holds the potential to impact the validity of results from previous findings using field stimulation.

  • Jennifer Donohue - Mechanical Engineering, SUNY Binghamton University

    Jennifer DonohoeEducational Institution: SUNY Binghamton University
    List of Mentors: Dr. Cary Pint & Kathleen Moyer
    Program: NSF REU
    Research Project: High Power alternative-ion batteries via co-intercalation
    Poster: NSF REU Jennifer Donohue Poster.pdf
    Research Abstract:   The rate-limiting de-solvation step required for graphitic intercalation of alkali ions has limited the use of modern batteries in high-power technologies like grid-energy storage and electric vehicles. The co-intercalation phenomenon observed in the presence of linear ethers allows for high-power devices through co-solvate intercalation, which effectively eliminates the rate-limiting de-solvation step. This phenomenon is observed not only with conventional lithium chemistries but also with alternative ion chemistries which promise reduced battery fabrication cost. Herein, we demonstrate high-rate potassium and sodium co-intercalation into graphite with specific capacities >100mAh/g at 5A/g. Prussian blue was also investigated as a high rate cathode and in its sodiated form showed specific capacities >100mAh/g at 10C. These results prove the viability of alternative-ion co-intercalation based batteries for use in low-cost high-power applications."

  • Crystal Nattoo - Electrical Engineering, University of Miami

    Crystal NattooEducational Institution: University of Miami
    List of Mentors: Dr. Sharon Weiss & Tengfei Cao
    Program: NSF REU
    Research Project: Porous Silicon on Glass for Low-Cost Diagnostics
    Poster: NSF REU Crystal Nattoo Poster.pdf
    Research Abstract:   In the search for approaches to improve medical diagnostics around the globe, the World Health Organization created the ASSURED criteria: Affordable, Sensitive, Specific, User-friendly, Rapid and Robust, Equipment-free, and Delivered to those who need it. Smartphone based lab-on-a-chip systems have the potential to satisfy the ASSURED criteria because of the widespread availability of smartphones, even in low resource environments. In this work, we report on the fabrication and characterization of a new type of optical transducers for a smartphone based lab-on-a-chip system using porous silicon thin films (PSiTF). The performance of the PSiTF sensor is evaluated on different substrates with both smartphones and traditional spectrometers. Porous silicon was selected because it is a versatile material with large specific area, easy surface modification, high optical quality and low fabrication cost, which makes it a promising candidate for multi-analyte detection in our system. Preliminary sensing results based on detection of different concentrations of glucose showed that a glass-PSiTF-paper sandwiched structure exhibits reproducible optical performance in a flow-cell setting using both smartphone and spectrometer detection schemes. In the smartphone detection scheme, image processing is performed on pictures taken of the sample under test to determine color changes that result from the introduction of analyte. In the spectrometer detection scheme, reflectance spectra shifts track the introduction of analyte. Future work will focus on correlation of the smartphone and spectrometer results to benchmark detection sensitivity using the smartphone. The demonstrated glass-PSiTF-paper system has strong promise for enabling smartphone based lab-on-a-chip systems to achieve ASSURED criteria for a variety of diagnostic applications. 

  • Alexandra Quinones Melendez - Chemical Engineering, University of Puerto Rice

    Alexandria Quinones MelendezEducational Institution: University of Puerto Rico
    List of Mentors: Dr. David Cliffel & Christopher Stachurski,  Dilek Dervishogullari
    Program: NSF REU
    Research Project: Oriented Interface of PSI and PSII for Solar Driven Hydrogen Evolution 
    Poster: NSF REU Alexandra Quinones Melendez Poster.pdf
    Research Abstract:   In response to a growing demand for alternative energy sources, many researchers consider hydrogen fuel as a strong contender for an emissions-free and sustainable energy source. Yet current methods for hydrogen fuel production can require expensive resources or elaborate designs to function properly.   Alternatively, there are a number of naturally occurring enzymatic processes with similar outcomes which could be utilized for fuel production. Photosystem I (PSI) and Photosystem II (PSII), which are the two key proteins in photosynthesis, are capable of acting in series in order to split water into hydrogen and oxygen. Our aim is to systematically functionalize both proteins allowing for their oriented assembly on a common conductive substrate, which would allow PSI and PSII to work in tandem . This work establishes a strategy to effectively short-circuit the photosynthetic pathway to sustainably generate hydrogen from sunlight in a self-contained device.  

  • Sarah Ruiz - Physics, Grinnell College

    Sarah RuizEducational Institution: Grinnell College
    List of Mentors: Dr. Jason Valentine & Zack Coppens
    Program: NSF REU
    Research Project: Graphene Processing for tunable Metasurfaces
    Poster: NSF REU Sarah Ruiz Poster.pdf
    Research Abstract:   Metamaterials enable optical properties that cannot be found in nature. Graphene has increasingly become an important component in some metamaterials due to its two-dimensional structure and potential for tunable applications.  Through the use of graphene intercalation, we seek to create a tunable perfect absorber metamaterial that can be used for low power visible displays. A design for this metasurface has been developed; however, graphene processing and characterization for the design have not been fully explored.  Here, we study exfoliation techniques and etch rates of graphene for fabrication of the metasurface. We characterized the etch rate for both aluminum and graphene using atomic force microscopy (AFM) to measure the step heights of graphene flakes. We found that aluminum and graphene etch at approximately the same rate of 0.8 nm/minute because of the low surface binding energy of aluminum and graphene relative to the kinetic energy of the incoming argon ions.

  • Mitchell Stokan - Chemical Engineering, University of Kentucky

    Mitchell StokanEducational Institution: University of Kentucky
    List of Mentors: Dr. Craig Duvall & Dr. Meredith Jackson & Sean Bedingfield
    Program: NSF REU
    Research Project: Screening of Novel Hydrophobically Modified Triblock Copolymers for Improved Stabilization of siRNA Polyplexes
    Poster: NSF REU Mitchell Stokan Poster.pdf
    Research Abstract:  Our lab has shown that diblock polymer-based siRNA nano-polyplexes (si-NPs), containing zwitterionic phosphorylcholine (PMPC) as the corona and a copolymer of dimethylamino ethyl methacrylate (DMAEMA), and butyl methacrylate (BMA) as the core, function as efficient vectors for siRNA delivery.  These polymers possess several desirable properties including lack of toxicity, pH dependent endosomal escape, long circulation half-lives, and high levels of tumor cell uptake and silencing activity. Here, we hypothesized that a third, hydrophobic block of polypropylene sulfide (PPS), would yield si-NPs with higher stability and biocompatibility due to added hydrophobicity and core stabilization.   The polyplexes were analyzed using ribogreen, luciferase, hemolysis, and fluorescence resonance energy transfer (FRET) assays to test for siRNA encapsulation, knockdown, endosomal escape, and stability respectively. The size of the nanoparticles formed were assessed using dynamic light scattering techniques by the Malvern Zetasizer. The polyplexes were tested at different N:P ratios and with or without palmitic acid hydrophobized siRNA-conjugates. Overall, the use of the polyphenylene sulfide block helped improve the encapsulation properties of the polymers and allowed for a higher efficiency in delivering the siRNA for gene knockdown.  With improved stability, the polymers could be readily used for circulation in the body with less of an effect on their performance.  These factors contribute to a better gene delivery system that allows for more success in drug delivery.

  • Donna Xia - Chemical and Biomolecular Engineering, University of Alabama, Tuscaloosa

    Donna XiaEducational Institution: University of Alabama, Tuscaloosa
    List of Mentors: Dr. Clare McCabe & Tim Moore
    Program: NSF REU
    Research Project: Self-Assembly of Stratum Corneum Lipid Bilayers Via Coarse-Grained Simulations
    Poster: NSF REU Donna Xia Poster.pdf
    Research Abstract:  The skin barrier function is localized to the lipid lamellae of the stratum corneum (SC), which is composed of ceramides (CER), cholesterol (CHOL), and free fatty acids (FFA). While this lipid composition is well-known, limited experimental resolution makes it difficult to uncover the molecular-level details of its organization. In this regard, molecular dynamics simulations offer atomic-level resolution, and can be used to study the effects of lipid composition on structural properties of SC lipid lamellae. However, the slow dynamics mean that systems are heavily influenced by their initial configurations. To bypass this effect, self-assembled structures are desirable. To reduce computational cost and allow self-assembly to be simulated, simplified coarse-grained models are used instead of their more detailed atomistic counterparts. In this study, different lipid compositions were self-assembled into bilayers, and structural properties, such as area per lipid, tilt angle, nematic order parameter, and lipid density profiles across the bilayers were examined. These properties were then compared across compositions to investigate the effects of lipid composition on bilayer structural properties. 

2016

  • Louis Apraku-Boadi - Chemistry, University of West Georgia

    Louis Apraku-BoadiEducational Institution: University of West Georgia
    List of Mentors: Dr. Janet Macdonald & Evan Robinson
    Program: NSF REU
    Research Project: Cu2S Nanocrystals as Signal Amplifiers for Biomolecule Detection
    Poster: NSF REU Louis Apraku-Boadi Poster.pdf
    Research Abstract:   The research concerning nanomaterials is a growing and interesting field of study. They have applications in targeted drug delivery, photovoltaics, and, as is the case in this study, diagnostics. A recently developed method in our lab allows the production of highly stable crystal-bound Cu2S nanocrystals. Unlike the more ubiquitous surface-bound ligands, crystal-bound ligands are integrated in high coordination number sites – greatly enhancing Cu2S nanocrystal stability. Cu2S crystals, though small, contain thousands of individual Cu atoms. Using various chromogenic copper chelators, this fact can be exploited and used in biochemical and biological assays. One such chelator is cuprizone, which forms a chromogenic bidentate complex with Cu that has an intense and characteristic absorption band. This provides an effective means of detecting Cu at M concentrations. Here we assess the stability of crystal-bound nanoparticles and the viability of the copper-cuprizone complex as a reporter.

  • Clayton Blythe - Physics/Economics, Central College of Iowa

    Clayton BlytheEducational Institution: Central College of Iowa
    List of Mentors: Dr. Kalman Varga & Jorge Salas
    Program: NSF REU
    Research Project: Simulation of High Harmonic Generation in Helium due to Bichromatic Counterrotating Circularly Polarized Laser Fields
    Poster: NSF REU Clayton Blythe Poster.pdf
    Research Abstract:   Attoscience is an important emerging area of research in modern atomic and molecular physics. In many electron-atom systems that are excited by femtosecond lasers, the recombination of an electron from the continuum occurs on the order of attoseconds. Precision on the sub-femtosecond and sub-angstrom scale will be necessary to probe the intricacies of light-matter interactions. High Harmonic Generation (HHG) is a technique that is growing in popularity for exploring these interactions. Harmonics with much higher frequencies and energies can be produced with various ellipticities. In this work, we present 3D Time Dependent Schroedinger Equation (TDSE) simulations combined with Time Dependent Density Functional Theory (TDDFT) for HHG in Helium. In this specific application, bichromatic counterrotating circularly polarized laser fields are employed, experimenting with various intensities, wavelengths, and pulse shapes. A circularly polarized fundamental is combined with its counterrotating second harmonic. The time-dependent electric field describes a Lissajous figure with threefold spatio-temporal symmetry resembling a clover. Dipole moment, ionization, and sensitivity to rotational symmetries are calculated, as well Fourier transformations employed to examine the intensity and ellipticity of emitted harmonics. Harmonics such as these with attosecond pulse lengths have potential applications in molecular and atomic chemistry such as photo-electron circular dichroism and x-ray magnetic circular dichroism.

  • Adam Boyer - Chemistry, Emporia State University

    Adam BoyerEducational Institution: Emporia State University
    List of Mentors: Dr. David Cliffel & Evan Gizzie
    Program: NSF REU
    Research Project: Controlling the Orientation of Photosynthetic Protein Assembly on Solid Surfaces: a Strategy for Improving Bio-derived Solar Cells
    Poster: NSF REU Adam Boyer Poster.pdf
    Research Abstract:   Current methods of harnessing energy have led to severe environmental impacts and necessitated the development of more conscientious methods, specifically solar cell conversion. Solar cell technology has attained efficiencies nearing 20% and is limited by high costs for processing silicon. One solution to this growing problem is implementing bio-derived solar cells with the photosynthetic protein, Photosystem I (PSI). Bio-derived solar cells provide remarkably clean energy production and utilizing Photosystem I affords a substantial supply of low cost material. Photosystem I acts as a pseudo-photodiode efficiently exciting electrons, and shuttling them unidirectionally through the protein; thus creating charge separation. However, harvesting the protein for solar cells leads to a mixed protein orientation on the solar cell surface. In order to maximize current flow, it is imperative that the orientation of PSI on a surface is controlled uniformly. In this work, Photosystem I was selectively modified with 2-iminothiolane during the extraction from spinach leaves while still thylakoid membrane bound. Following purification, modified PSI was allowed to self-assemble onto gold surfaces via high-affinity gold-thiol interactions. Once self-assembled onto the gold surface, photoelectrochemical analyses and highly resolved topography mapping techniques (i.e. Scanning Tunneling Microscopy) were utilized to investigate the photocurrent production under illumination and orientation of Photosystem I on the gold surface. Future applications of this exciting research includes considerable advances in bio-sensors and bio-technologies.

  • Timera Brown - Biology, Tougaloo College

    Timera BrownEducational Institution: Tougaloo College
    List of Mentors: Dr. Eva Harth & Dian Beezer
    Program: NSF REU
    Research Project: Regenerative Medicine: Synthesis of Functionalized Polyglycidol Building Blocks for Diverse Network
    Poster: NSF REU Timera Brown Poster.pdf
    Research Abstract:   Currently, a main focus of regenerative medicine is limited to embryonic stem cells as well as in vitro cell maturation. However, a more diverse approach using network forming materials is emerging as an innovative concept. Regenerative medicine is an interdisciplinary field of biomechanics which is geared toward the bioengineering and implementation of human cells, tissue, and/or organs in order to restore expected function. For example, currently in many knee operations where cartilage must be replaced, cartilage must be extracted and manipulated from cadavers or either grown from chondrocytes before being inserted into the patient. However, as an alternative to the delicate and time-consuming process of cartilage extraction and growth, this cartilage can be engineered through via polymeric networks. My project centers on acrylate-polyglycidol functionalization which due to the compound’s reactivity could combine with other materials and networks to lead to a robust polymer network with tunable crosslinking. This tunable amount of crosslinking could lead to the engineering of scaffolds of multiple sizes that could mimic not only cartilage tissue but potential other tissues such as dermal, bladder and liver tissues.

  • Kaleigh Ellis - Chemistry, Saint Mary's College

    Kaleigh EllisEducational Institution: Saint Mary's College
    List of Mentors: Dr. Sandra Rosenthal & Kemar Reid
    Program: NSF REU
    Research Project: Engineering CdSSe-CdS Core/Shell Quantum Dots for Use in Single-Protein Imaging
    Poster: NSF REU Kaleigh Ellis Poster.pdf
    Research Abstract: Semiconductor nanocrystals, or quantum dots (QDs), play an important role in in vivo single-protein imaging due to their size-tunable optical properties. However, the synthesis of QDs that are ideal for biological imaging - namely that they have a narrow size distribution, retain high quantum yields (QYs), and are photostable - is difficult due to interior and surface-related defects, including the interaction of the electron-hole pair with the QD’s environment. By growing an inorganic shell onto the QD to passivate the QD the QY and photostability can be increased. The goal of this research is to optimize the QY and stability of alloyed CdSSe QDs by growing a CdS shell onto the alloyed cores and to study their photoluminescence and structural properties using fluorimetry and transmission electron microscopy (TEM), respectively. Two shell growth methods are explored: one using successive ion layer adsorption and reaction (SILAR) techniques with cadmium(II)-oleate and sulfur precursors to grow successive monolayers of CdS shell, and a second continuous infusion method in which Cd(II)-oleate and octanethiol are infused slowly over the course of the shell-growth process. Initial results indicate that the continuous infusion method is the preferred procedure, producing higher quantum yields and a narrow size distribution while also requiring less reaction time than the SILAR method. These brighter and more size-uniform CdS-shelled QDs have the potential to revolutionize the use of QDs in in vivo single-protein imaging.   

  • Yasmin Graham - Mechanical Engineering, University of Maryland, Baltimore County

    Yasmin GrahamEducational Institution: University of Maryland, Baltimore County
    List of Mentors: Dr. Sharon Weiss & Yiliang Zhou
    Program: NSF REU
    Research Project: Low Cost Portable Biosensors Made From Porous Silicon Annular Bragg Resonators
    Poster: NSF REU Yasmin Graham Poster.pdf
    Research Abstract:   Point of care testing is a form of medical diagnostic testing which takes place at a patient’s bedside or directly at an active site. Our research is aimed at creating low cost, low power, high quality, portable biosensors that enable color-based detection and can be easily integrated with mobile devices such as a smartphones. The biosensing platform explored in this work is an annular Bragg resonator (ABR) on a porous silicon (PSi) substrate. ABRs are radially symmetric structures that possess a discrete refractive index profile that creates a cavity region surrounded by highly reflecting mirrors.  These structures have been traditionally used to resonantly enhance the emission of fluorescent molecules incorporated in the cavity region. PSi, a nanostructured material formed by electrochemical etching of a silicon substrate, possesses a large surface area which is highly advantageous for capturing large quantities of molecular species inside the pores. To form a colorimetric biosensor, colloidal AgInS2/ZnS quantum dots (QDs) are infiltrated into PSi ABRs; the ABR modifies the QD emission, leading to a structure with a relatively narrow and distinct fluorescence spectrum.  Since the QDs only cover a portion of the internal pore surface area, the remainder of the pore surface is available to selectively capture desired target molecules when appropriately functionalized.  Target molecule binding in the pores modifies the ABR resonance wavelength and consequently shifts the peak emission wavelength of the embedded QDs. Hence, molecular binding events lead to a biosensor color change. The QDs embedded in PSi ABRs were excited with a 532 nm laser and the fluorescence emission was collected with a Raman microscope equipped with a 100x objective lens. An 8-fold enhancement of the peak QD intensity was measured when the QDs were embedded in a PSi ABRs compared to a planar PSi film.  A preliminary experiment to detect 5 µM of Catalase protein caused a 30nm average shift of the QD photoluminescence peak which indicates that this platform has the potential to achieve highly sensitive biosensing.

  • Marne Helbing - Engineering, University of Tennessee, Martin

    Marne HelbingEducational Institution: University of Tennessee, Martin
    List of Mentors: Dr. Florence Sanchez & Yonathan Reches
    Program: NSF REU
    Research Project: Reactivity of Nano-Particles in Cementitious Systems
    Poster: NSF REU Marne Helbing Poster.pdf
    Research Abstract:   Nano-particles (NP’s) have been studied as additives for improving the mechanical and durability properties of cement-based materials. The contributions of NP’s to the cement system have been attributed to their high surface area to volume ratio, although the specific chemical interactions between NP’s and the cementitious system have yet to be defined. The intrinsic and catalytic reactivity of NP’s in cement-based systems were studied, including the effect of cement chemistry on the agglomeration of NP’s. NP’s were reacted with real and simulated cement systems, and their reaction products were characterized chemically and microstructurally. The effects of cement on the surface charge and agglomerate size of the NP’s were simulated using salt solutions and observed by dynamic light scattering (DLS). It was demonstrated that for the nano-TiO the nano-particles agglomerated to approximately 102 NP’s/agglomerate. Agglomeration further increased due to the effects of the ions in the salt solutions.

  • Eion Hindsman-Curry - Applied Physics/Mechanical Engineering, Morehouse College

    Eion Hindsman CurryEducational Institution: Morehouse College
    List of Mentors: Dr. Richard Haglund & Claire Marvinney
    Program: NSF REU
    Research Project: Enhanced Porosity and Exciton-Phonon Coupling in Zinc Oxide Nanopopcorn
    Poster: NSF REU Eion Hindsman-Curry Poster.pdf
    Research Abstract:   Semiconductor zinc oxide (ZnO) nanostructures are acclaimed as efficient optoelectronic materials and stable light emitters at room temperature.  Zinc oxide features a wide bandgap (3.37 eV) and a stable exciton (Ebinding=60 meV), and nanostructured ZnO used for various applications such as gas sensors, photocatalysts, nanolasers, etc. [1] A novel ZnO nanostructure, christened “nanopopcorn”, has been fabricated by a modified vapor solid method, evaporating Zn in a chamber at a temperature of 700°C to bond with O2 gas on a GaN substrate. The free-form crystalline structure has a high porosity, among other attributes, making it ideal for biological and molecular sensing. Zinc oxide nanopopcorn displays an enhanced surface area to volume ratio compared to planar and one-dimensional nanostructures and has multiple distinct exciton binding peaks.  Using image analysis on select samples, a consistent surface area to volume ratio is observed of about 0.023:1 nm-1. This ratio is enhanced over that of ZnO nanowires, a commonly used nanostructure for optoelectronics and sensing applications. The higher surface area creates more bonding sites with the surrounding material, making ZnO nanopopcorn useful for optoelectronic enhancement techniques such as exciton-phonon and exciton-plasmon interactions. The exciton-phonon coupling and the exciton-plasmon coupling create novel vibrational and optical modes, respectively.  Studying these fundamental properties will help us to fully characterize the physical and electronic properties of this novel material. Given these properties, ZnO nanopopcorn may be an ideal sensor for many medical and biological applications such as cancer cell detection [3] and electrochemical glucose sensing [4].

    1. Wang, X., Liu, W., Liu, J., Wang, .F, Kong, J., Qiu, S., He, C. and Luan, L. “Synthesis of Nestlike ZnO Hierarchically Porous Structures and Analysis of Their Gas Sensing Properties” Applied Materials and Interfaces, 4, 817-825 (2012).
    2. Politi, J., Rea, I., Dardano, P., De Stefano, L. and Gioffre, M. “Versatile synthesis of ZnO nanowires for quantitative optical sensing of molecular biorecognition” Sensors and Actuators B: Chemical, 220, 705-711 (2015).
    3. Sudhagar, S., Sathya, S., Pandian, K. and Lakshmi, B. “Targeting and sensing cancer cells with ZnO nanoprobes in vitro” 33, 1891-1896 (2011).
    4. Ali, S. “Fabrication and characterization of ZnO nanostructures for sensing and photonic device applications” Linköping Studies in Science and Technology Dissertation No. 1412, (2011).

  • Tao Hong - Engineering Science, CUNY Queensborough Community College

    Tao HongEducational Institution: CUNY Queensborough Community College
    List of Mentors: Dr. Deyu Li & Lije Yang
    Program: NSF REU
    Research Project: A Microfluidic Device for Sorting C. elegans
    Poster: NSF REU Tao Hong Poster.pdf
    Research Abstract:   Caenorhabditis (C.) elegans locomotion is a stereotyped behavior by generating waves of dorsal-ventral bends and propagating them forward along its body from head to tail. Noticeably absent from the C. elegans literature, however, are studies of evaluating the motility of nematode in waved-like channels in the microfluidic device. Major applications of immobilizing nematode are related to pressure involved process in the straight narrow-down channels. This presentation focus on studying of the spontaneity of mobility for C. elegans in wave-like channels. By utilizing this unique spontaneity, we designed and fabricated a microfluidic device which can sort and immobilize C.elegans from a colony mixed with nematodes in different larvae stage. The front part of channels in this microfluidic device is waved-like with the 30-micron diameter, so that only the fit-sized nematodes can swim in spontaneously and trapped in the body part which is straight and narrow down to 20 microns. Most medicine stimuli application of C.elegans is carried on synchronized well-fed young adults cultivated from only eggs with diameter vary from 30-35 micros. Synchronizing C.elegans by old method is labor-intensive and time-consuming.  This design performs a convenience to separate nematodes within any region of diameter from an unsynchronized colony, thus enhance of the efficiency of immobilization and further biological stimuli of C. elegans.

  • Ayisha Jackson - Engineering, Brown University

    Ayisha JacksonEducational Institution: Brown University
    List of Mentors: Dr. Craig Duvall & Dr. Meredith Jackson & Thomas Werfel
    Program: NSF REU
    Research Project: The Use of Microfluidic Mixing Devices for Minimizing Polyplex Nanoparticle Size and Increasing Tumor Penetration
    Poster: NSF REU Ayisha Jackson Poster.pdf
    Research Abstract: Despite the use of various formulation methods for the polyplex packaging and delivery of siRNA, current polyplex formulations remain inconsistent with poor shelf life, and often particles that are too large to allow sufficient penetration of tumor tissue. To solve these formulation challenges, the Lee Visco-Jet Micro-mixer has been used to examine methods of improving siRNA polyplex formulation due to its ability to increase turbulence and particle interaction; varying flow-rate settings to determine optimal conditions. Dynamic light scattering (DLS) was used to quantify the micro-mixer’s effect on PEGylated micelles’ size and polydispersity; using multiple polymers with DMAEMA and BMA cores and varying coronas. To test particle stability, the hand-mixed and micro-mixed particles were compared after lyophilization and reconstitution. Furthermore, a Ribogreen assay was used to determine the encapsulation efficiencies of each particle formulation method.Overall, these tests have shown that the use of the micro-mixer consistently minimizes particle sizes from a hand-mixed average of around 100 nm to around 60 nm. The micro-mixer also significantly improves the encapsulation efficiency of siRNA during formulation from an average of 65% up to almost 80%. Further studies will include examining the effects of excipient additions for increased long-term stability of nanoparticles. Additionally, further studies will include in vitro testing of micro-mixed nanoparticle performance on tumor penetration using 3D matrigel-based models. These studies also show that the micro-mixed particles were more stable after freeze-drying and reconstitution than the hand-mixed counterparts. The above mentioned results indicate the ability of micro-mixer use to provide optimal complexing processes for clinical practice.

  • Amira Kessem - Renewable Energy Engineering, Alfred University

    Amira KessemEducational Institution: Alfred University
    List of Mentors: Dr. David Cliffel & Dr. Kane Jennings & Dr. Jeremy Beam
    Program: NSF REU
    Research Project: Strategies for Scaling Up Solid State Photosystem I-based Devices for Solar Energy Conversion
    Poster: NSF REU Amira Kessem Poster.pdf
    Research Abstract: In order to commercialize solid state solar cell devices, it is important to show that they can be scaled up to industrially relevant sizes. Photosystem I (PSI)-based solid state devices for solar energy conversion have shown to yield an appreciable photocurrent over small surface areas. However, devices with larger surface areas have so far not been synthesized. This research project focuses on the fabrication and testing of solid state PSI-based solar cell devices of 4cm diameter and 6cm diameter. It includes two device architectures: p-Si/PSI/ZnO and TiO2/PSI-polyaniline.

  • Anne Leonhard - Chemical Engineering/Computational Science, Rose-Hulman Institute of Technology

    Anne LeonhardEducational Institution: Rose-Hulman Institute of Technology
    List of Mentors: Dr. Clare McCabe & Tim Moore
    Program: NSF REU
    Research Project: Coarse-Grained Simulations of the Self-Assembly of Skin-Relevant Lipid Structures
    Poster: NSF REU Anne Leonhard Poster.pdf
    Research Abstract:   The barrier properties of the skin are largely governed by the lipid lamellae of the outermost layer of skin, the stratum corneum (SC). While the composition of the SC is known, the molecular-level features of the lipid organization are not. This information would be useful for repairing an impaired skin barrier or selectively bypassing the barrier, e.g., for transdermal drug delivery. Molecular simulation allows precise control over system composition and direct visualization of the system structure, making it a useful tool for studying such systems. The slow kinetics of lamellar self-assembly make using atomistic models computationally inefficient. Thus, coarse-grained models, where groups of atoms are treated as individual interaction sites, are employed to study the self-assembly of SC lipids. Here, coarse-grained models of SC lipids, including CER NS C16, CER NS C24, cholesterol, and free fatty acids, are simulated to gain insight into the low-energy structures adopted by mixtures of these lipids. Self-assembly of both single and stacked bilayers in solution is studied by cooling systems from a high-temperature, disordered state. Structural properties, such as lipid positioning, angle between lipid tails, tilt angle of lipid tails, nematic order parameter, and bilayer lipid density are calculated. These properties are compared between simulations to determine the effects of lipid concentration on bilayer structure. This research increases understanding of the structural role of various lipids in SC organization and is an important step in the use of accurate coarse-grained models of the SC lipids.

  • Clara Simons - Physics/German, Wofford College

    Clara SimonsEducational Institution: Wofford College
    List of Mentors: Dr. Kane Jennings & Max Robinson
    Program: NSF REU
    Research Project: Photocatalytic Photosystem I/PEDOT Composite Films Prepared by Vapor Phase Polymerization
    Poster: NSF REU Clara Simons Poster.pdf
    Research Abstract:   Photosystem I (PSI) is a globally abundant protein complex that facilitates the light reactions of photosynthesis in green plants and cyanobacteria with near-unity quantum efficiency, and has been used in solid state cells and hydrogen production. Extracted PSI can also be rapidly assembled atop conductive surfaces for photocatalytic response. We report the incorporation of PSI proteins within an electrically conductive poly(3,4-ethylenedioxythiophene) matrix using a vapor phase approach, allowing for the desired increase of impedance and conductance in our films. The inclusion of Friedel-Crafts catalyst (FeCl3) within drop cast solutions of PSI permits subsequent polymerization when in contact with an appropriate monomer, while an ideal amount of surfactant (Triton X-100) improves film smoothness and uniformity. Using these techniques, we observe optimal photocurrents of nearly 1 μA/cm2 over control films when 6μM PSI is included in the drop cast solution. PSI’s absorbance spectrum has a characteristic peak at 675nm, which is indicative of its red light absorption and photocatalysis and which contributes significantly to photocurrent outputs following the vapor phase deposition of our polymer. Due to the significant red light photoresponse contribution of composite films, we suggest their use within light-activated counter electrodes in dye-sensitized solar cells.

2015

  • Christopher Banks - Physics, Norfolk State University

    Christopher BanksEducational Institution: Norfolk State University
    List of Mentors: Dr. Rizia Bardhan & Naiya Soetan
    Program: NSF REU
    Research Project: Analysis of the Catalytic Effects of Multi-branched Gold Nanostructures (MGNs) on the Kinetics of the Degradation of P-nitrophenol (PNP)
    Poster: NSF REU Christopher Banks Poster.pdf
    Research Abstract:  Recently, interest in metallic nanoparticles has skyrocketed. Applications using nanoparticles include photo-thermal biomedical uses, fuel cell technology, and constructing sensors based on localized surface plasmon resonance (LSPR). A type of nanoparticles known as multi-branched gold nanostructures (MGNs) are exceedingly interesting because their size and shape are tunable based on the pH and the concentration of 4-(2-hydroxyethyl)-1-piperazineethanesulfonic Acid (HEPES) and the concentration of HAuCl4 in the solution, in which the MGNs are suspended. The customizability of the size and shape of MGNs allows for use in various applications, because they enable optical tunability and the plasmonic enhancement of materials. We investigated the effects of the morphology of the MGNs on catalytic activity by observing their catalysis of the degradation of p-nitrophenol (PNP) to p-aminophenol (PAP) in the presence of sodium borohydride (NaBH4). Previous work shows that this reaction follows the Langmuir-Hinshelwood model. We found that the degradation of PNP on the surfaces of MGNs with plasmon resonances at ~680 nm and ~800 nm follow the Langmuir-Hinshelwood model in that the apparent rate constant, kapp,decreases as the concentration of PNP increases. These results will be useful for future research in MGN surface area and morphology and other metallic nanoparticle morphology including bimetallic nanoparticles, biosynthesized nanoparticles or other types of nanoparticles made from noble metals.

  • Ben Burdette - Chemical Engineering, University of Kentucky

    Ben BurdetteEducational Institution: University of Kentucky
    List of Mentors: Dr. Craig Duvall & Brian Evans
    Program: NSF REU
    Research Project: Testing Fabrication Conditions to Optimize Properties of Peptide-Loaded Nanoparticles
    Poster: NSF REU Ben Burdette.pdf
    Research Abstract:   The use of peptide-, protein-, and nucleic acid-based therapeutics has increased drastically due to the advantages they hold in terms of potency, specificity, and biocompatibility compared to commonly-utilized small molecule drugs. However, biomacromolecular therapeutics are limited by poor cellular uptake and susceptibility to proteolytic degradation, spurring the development of nanoparticle based systems that can protect biologic cargo and facilitate cellular internalization.  To realize the clinical translation of these nanoparticle-based systems, the parameters affecting synthesis need to be highly controlled to consistently yield an optimized drug delivery vehicle. Here, we studied the effect of various synthesis parameters on the formation of pH-responsive, electrostatically complexed nanoparticles for the intracellular delivery of an established therapeutic MAPKAP Kinase 2 inhibitory peptide.  Specifically, we studied the influence of ionic strength, solute concentration, and lyophilization/reconstitution on particle morphology and stability.  Upon investigating the impact of the charge ratio [CR: the molar ratio of the number of negatively charged carboxylates (COO-) moieties on the polymer to the number of positively charged primary amines (NH2+) present in the peptide) on nanoparticle synthesis, we found that a CR of 1:3 demonstrated robust complexation without aggregation. An important question for clinical translation is whether nanoparticles can be reconstituted and remain active following long-term storage as a lyophilized powder. Results were promising, as Lyophilization of our particles appeared to result in more monodisperse, smaller particles, and the size of lyophilized particles was inversely proportional to the ionic strength of the buffer used during lyophilization. These results indicate that nanoparticle morphology, polydispersity, and stability can be controlled by modulating specific parameters utilized during nano-scale synthesis. Flow cytometric quantification of the effect of particle fabrication conditions on cell uptake is ongoing.  Future work will involve investigation of the effect of formulation conditions on peptide bioactivity.  We ultimately seek to provide a framework for repeatable, optimized nanoparticle synthesis for the clinical translation of biomacromolecular therapeutics such as the MAPKAP Kinase 2 inhibitory peptide showcased herein.

  • Thomas Campbell - Engineering Physics, Murray State University

    Thomas CampbellEducational Institution: Murray State University
    List of Mentors: Dr. Richard Haglund & Robert Marvel
    Program: NSF REU
    Research Project: Characterization of vanadium dioxide by scanning probe microscopy
    Poster: NSF REU Thomas Campbell Poster.pdf
    Research Abstract:  Vanadium dioxide (VO2) experiences a phase transition from a monoclinic, semiconductor phase to a rutile, metallic phase, during which a vast change in physical, thermal, electrical, and optical properties are observed.  This transition, which can easily be induced by temperature change, optical pumping, or electric field, makes VO­2 an attractive material for applications in a wide range of device fabrication, from waveguide couples to passive thermal cooling devices.  The implementation of VO2 thin films onto micro- or nanoscale device structures necessitates the use of more advanced phase transition characterization techniques, as simple optical reflection or transmission experiments will no longer be viable in complicated device architectures.  This research project explores the feasibility of using Scanning Probe Microscopy (SPM) techniques to characterize and study the propagation of the vanadium dioxide phase transition in thin films.  Specifically, Scanning Tunneling Microscopy (STM) and Scanning Thermal Microscopy (SThM) techniques are discussed, with corresponding images.

  • Alyssa Cartwright - Electrical Engineering, Massachusetts Institute of Technology

    Alyssa CartwrightEducational Institution: Massachusetts Institute of Technology
    List of Mentors: Dr. Sharon Weiss & Gilberto Rodriguez
    Program: NSF REU
    Research Project: Detection of Specific DNA Sequences using Porous Silicon Photonic Crystal Nanobeams
    Poster: NSF REU Alyssa Cartwright Poster.pdf
    Research Abstract:  In this work, porous silicon (PSi) photonic crystal (PhC) nanobeam biosensors are computationally and experimentally demonstrated for the detection of specific DNA sequences. The structures are composed of a linear array of air holes forming mirror and cavity regions, which are lithographically etched into a PSi waveguide. The large internal surface area of the PSi substrate increases the probability of target molecule capture and increases the interaction between target molecules and light guided in the structure. The transmission spectra of the PSi nanobeams are characterized by a resonant peak within a photonic bandgap region, thus overcoming the potential limitations imposed by the free spectral range of ring resonator structures.  Design studies revealed that the air hole spacing is the most critical parameter in determining the resonance wavelength. Quality (Q) factors as high as 5000 have been experimentally measured for the PSi nanobeams. When an analyte is introduced within the pores of the nanobeam structure, the effective refractive indices of the structure are increased, resulting in a measurable shift of the resonance wavelength. The magnitude of this spectral shift directly correlates to the size and quantity of analyte introduced. The label-free detection of a 16-base DNA sequence is conducted by first functionalizing oxidized PSi nanobeams with the linker molecule, 3-aminopropyltrimethoxysilane (3-APTES), and then a 16-base PNA probe that is synthesized in-situ.  Complementary and non-complementary 16-mer DNA are exposed to the functionalized PSi nanobeams and selective detection is demonstrated.  The PSi nanobeam demonstrates an approximate 40-fold improvement in small molecule sensitivity over standard silicon-on-insulator (SOI) nanobeam biosensors, which is in good agreement with field confinement simulations. The merging of the PSi material with the compact, high Q-factor PhC nanobeam design results in the highest reported nanobeam sensitivity to date with a reduced fabrication cost when compared to traditional SOI devices.

  • Dion Casey - Engineering Mathematics, St. Augustine's College

    Dion CaseyEducational Institution: St. Augustine's College
    List of Mentors: Dr. Yaqiong Xu & TianjiaoWang
    Program: NSF REU
    Research Project: Fabrication and characterization of 2D materials
    Poster: NSF REU Dion Casey Poster.pdf
    Research Abstract:   Since the discovery of single layer graphene in 2004, the research field of 2-Dimensional (2D) material became very appealing. 2D material such as graphene, boron nitride (BN), and transition metal dichalcogenides (TMDCs) have unique electrical, optical, and mechanical properties that can be used in a wide range of applications. 2D material can be obtained in various methods, Chemical vapor deposition, Liquid phase exfoliation, etc. The method we used is the primary and most effective method is Mechanical exfoliation. Mechanical exfoliation is a physical process which gives the best results in purity and mobility of 2D material, rather than the other chemical processes. In this project we fabricated and characterized graphene and molybdenum disulfide based transistors/heterostructures. Graphene is single layer of carbon atoms arranged in a hexagonal lattice with a band gap of zero. Monolayer molybdenum disulfide (MoS2) has a triangular prismatic lattice and a direct band gap of 1.8eV. MoS2 and Graphene flakes were mechanically exfoliated from their bulk materials and then transfer to a degenerately doped 290 nm SiO2/Si substrate to build transistors/heterostructures . Then electrodes were fabricated using electron-beam lithography then thermal evaporation of Cr and Au. By studying the electrical and optical properties of these structures will offer a new way optimize optoelectronics devices.

  • Corey Combs - Materials Science, University of Tennessee, Knoxville

    Corey CombsEducational Institution: University of Tennessee, Knoxville
    List of Mentors: Dr. Sokrates Pantelides & Xian Shen
    Program: NSF TN-SCORE
    Research Project: Discovery of Unusual Structural and Electronic Properties in Monolayer and Multilayer Si2Te3
    Poster: NSF REU Corey Combs Poster.pdf
    Research Abstract:  Silicon telluride, a two-dimensional chalcogenide, could potentially bring unique 2d material properties to the fields of thermal and optical sensing.  Determined experimentally, silicon telluride, Si2Te3, assumes a two-dimensional layered crystal structure.  Not much is known of this material’s electronic properties, except that it is a p-type semiconductor with an experimentally determined indirect band gap close to 1 eV.  The tellurium forms a hexagonal close packed lattice, and the silicon sits in pairs in alternating layers of the material.  These silicon pairs occupy one of four possible orientations within the layers, three of which lie along the plane of the layer, and the fourth is orthogonal to the first three.  This gives rise to high variability concerning the electron band structure of the material, due to a near limitless number of possible combinations of the silicon dimer orientations.  Using molecular dynamics simulations, we see that the silicon dimers switch orientations without much difficulty at finite temperatures.  We also see that, if the majority of silicon dimers have the same orientation, the lattice constant will expand along the direction of the dimers.  Because of this, we believe strain could be used to control the orientation of the dimers.  As changes in temperature have a large effect on the properties of the electron band structure, this material could be useful in both optical and thermal sensing applications.

  • Marc Cummingham - Chemical Engineering, University of California, Berkeley

    Marc CunninghamEducational Institution: University of California, Berkeley
    List of Mentors: Dr. Peter Pintauro & Junwoo Park
    Program: NSF REU
    Research Project: Electrospun Nanofiber Bipolar Membranes
    Poster: NSF REU Marc Cunningham Poster.pdf
    Research Abstract:   Bipolar membranes (BPMs) consist of cation exchange and anion exchange membranes stacked together leading to formation of a bipolar junction at the interface. In an electrochemical cell, BPMs enable water splitting into protons and hydroxide ions. Unlike in standard water electrolysis, water splitting in BPMs occurs without the evolution of hydrogen and oxygen gas. Thus water splitting can theoretically occur at 0.83V, significantly lower than 1.23V required in electrolysis. A significant amount of energy (about 60%) can be saved. The key applications of BPMs include commodity chemical production, waste recycling, and water purification. Recently, attempts to use BPMs in fuel cells have also been reported. In my work, the fabrication of bipolar membranes via electrospinning was investigated. Electrospinning allowed for careful control of the BPM composition, morphology, and thickness. BPMs were electrospun as fiber mats and densified into membranes via solvent exposure and hot pressing. The key novelty was the introduction of a 3D bipolar junction by dual-fiber cospinning of anionic and cationic nanofibers. The membranes were tested in an electrodialysis cell where current-voltage curves were recorded. The composition and thickness of the bipolar junction was varied. Preliminary testing has shown increasing junction thickness relative to the ion exchange layers decreases the water splitting potential but also reduces selectivity. The best performing bipolar membrane fabricated had a total thickness of 30 microns, a 3 micron 3D bipolar junction, and an extrapolated water splitting potential of 0.95V. In terms of future work, the introduction of catalysts at the junction could further improve electrospun bipolar membrane performance. 

  • Autumn Douthitt - Chemical Engineering, Tennessee Technological University

    Autumn DouthittEducational Institution: Tennessee Technological University
    List of Mentors: Dr. Richard Haglund  & Christina McGahan
    Program: NSF TN-SCORE
    Research Project: Modeling of Au:VOPlasmon Nanomodulators
    Poster: NSF REU Autumn Douthitt Poster.pdf
    Research Abstract:  On-chip communication is currently the principal limiting factor in computer speed.  Optical modulators could replace electronic switches and interconnects on computer chips, carrying data by light pulses instead of electrical signals.  This would greatly increase speed while reducing electrical resistance and heat generation. Plasmonic devices built from metal nanostructures can be used to transmit and manipulate light on a sub-wavelength scale, reducing the modulator footprint. In this research project, the goal is to improve upon signal processing using optical modulators by simulating electromagnetic waves propagating through a gold:vanadium dioxide (Au:VO₂) dimer placed on a glass substrate using a finite-difference, time-domain (FDTD) modeling software (Lumerical® Solutions). Such dimers have recently been described as efficient photon modulators.1 Normalized data after repeating the Au:VO₂ computations reproduced those results. We hypothesized that dimers comprising gold nanorods and VO2 nanodisks would produce narrower resonances than the nanodisk dimer, resulting in higher contrast and optimized signal switching. FDTD simulations assessed the ideal aspect ratios for nanorods placed on a glass substrate. The results harvested from rod and disk simulations compared favorably with experimental observations.2 Working towards combining these studies, we have found that small (4nm) gaps between VO2 disks and Au particles with higher aspect ratios affect the plasmon resonance shift as the VO2 switches, seen previously for disk dimers.1
    1Appavoo, K. and Haglund, R. F., “Polarization selective phase-change nanomodulator,” Scientific Reports 4, 6771 (2014). 2. Sönnichsen C, Franzl T, Wilk T, von Plessen G, Feldmann J. “ Drastic reduction of plasmon damping in gold nanorods,” Phys Rev Lett 2002, 88:077402. *Research partially supported by the Office of Science, United States Department of Energy (DE-FG02-01ER45916)

  • Dennis Ejorh - Mechanical Engineering, Tennessee Technological University

    Dennis EjorhEducational Institution: Tennessee Technological University
    List of Mentors: Dr. Cary Pint & Rachel Carter
    Program: NSF TN-SCORE
    Research Project:
    Porous Silicon Templated Nanoporous Carbons for Tunable Li-S Battery Electrodes
    Poster:
    NSF REU Dennis Ejorh Poster.pdf
    Research Abstract:   Lithium-ion batteries have proven to be the universal standard for commercial battery technology. However, materials that comprise conventional lithium-ion battery electrodes are expensive and environmentally scarce (e.g. lithium, cobalt, etc.). Lithium- Sulfur batteries are currently viewed as the likeliest potential replacement for conventional lithium-ion electrodes, boasting high theoretical capacity about 6 times higher than conventional lithium-ion. In this work, we aim to promote an economically innovative means of fabricating high-performance electrode material, through the implementation of scalable processes and utilization of low-cost process materials: Silicon and Carbon. With fabrication of mesoporous carbon by means of Chemical Vapor Deposition on a highly controllable template such as nanoporous Silicon and subsequent Sulfur penetration, a high-quality cathode material is made; furthermore, the mesoporous nanostructure serves to improve cycle performance (the current focus in Li-S batteries) by preventing irreversible electrochemical reactions through encapsulation of sulfur atoms (allowing volumetric expansion of lithium-polysulfides) within the network formed by carbon meso-pores. Optimal device performance results of ~1360 mAh-gsulfur -1 (at a ~.1A/g current loading) upon initial charge/discharge cycling and subsequent cycle capacities of ~1000 mAh-gsulfur -1 have been shown; thus validating the feasibility of future industrial translation.

  • Yi Jane Jiang - Liberal Arts & Science, Queensborough Community College

    Jane JiangEducational Institution: Queensborough Community College
    List of Mentors: Dr. Kane Jennings & Maxwell Robinson
    Program: NSF REU
    Research Project: Macroporous TiO2 Photoanodes for High Efficiency PSI-Based Biohybrid Photovoltaics
    Poster: NSF REU Jane Jiang Poster.pdf
    Research Abstract: Photosystem I (PSI) is a protein complex residing within chloroplast of photosynthetic organisms. It is being studied as a candidate for dye-sensitized solar cell (DSSC) because it converts solar radiation to electrons with near-unity internal quantum efficiency. One of the obstacles that hinder PSI from being a more widely used dye is its large size. It is difficult to get sufficient PSI loaded throughout the photoanode of DSSC, a layer of titania (TiO2) nanoparticle coating, because the regular titania coating is mesoporous (pore size less than 50 nm).

    This presentation focuses on designing macroporous titania coatings with pore size as large as 1000 nm so that integration between titania coating and PSI would be enhanced. Sacrificial templating technique is employed to incorporate porosity into titania paste using oil-in-water emulsion and polystyrene latex as templating materials. The templated titania paste has been made directly from titanium dioxide powder. Then a titania coating has been produced on fluorine doped tin oxide (FTO) glass by doctor blading. The resulting coatings are uniform and crack-free. Scanning electron microscopy shows that the templated titania coatings have high porosity and interconnected meso and macro pores. They also demonstrate increased absorbance of PSI according to UV-Vis photospectroscopy. Using the macroporous titania coating as a photoanode would potentially enhance the overall efficiency of PSI-based biohybrid photovoltaics due to the high integration of PSI and titania coating. Further research will be carried to understand the effect of the added porosity on PSI and titania interface through cell performance studies.

  • Jack Lewis - Engineering Science, Trinity University

    Jack LewisEducational Institution: Trinity University
    List of Mentors: Dr. Cary Pint & Keith Share
    Program: NSF REU
    Research Project: Optimal Composition of Tungsten Diselenide (WSe2) Electrodes in Sodium Ion Batteries
    Poster:
    NSF REU Jack Lewis Poster.pdf
    Research Abstract:   This project explores for the first time the use of tungsten diselenide (WSe2) as an electrode material in sodium ion batteries. Using CMC as the binder and a mixture of EC:DEC as the electrolyte, we have achieved a 2nd discharge capacity of 225 mAh/g and retention of 69% after 25 cycles. Sodium ion batteries have recently attracted more attention as a viable energy storage method, due to the natural abundance of sodium and similarities to lithium ion technology. WSe2 is a transition metal dichalcogenide (TMD), and is comprised of a layered structure similar to graphite. Because of the large size of sodium, WSe2 is susceptible to damage caused by the insertion and removal of ions during cycling of the battery. Therefore, it is important that we select additive materials that will optimize the performance of our batteries. By determining which binders and electrolytes work well, we can drastically improve the capacity of the battery and how well it cycles. Charge/discharge tests were conducted to determine how each composition performed. This method gave us a way to measure the cell’s capacity and degradation, which we could use to compare different cells. For the future, we want to create nanostructured WSe2 to further improve the performance.

  • Sharon Lin - Chemical Engineering, University at Buffalo

    Sharon LinEducational Institution: University at Buffalo
    List of Mentors: Dr. Rizia Bardhan & May Ou
    Program: NSF REU
    Research Project: IR Laser Triggered Chemo-photothermal Treatment of Doxorubicin Resistant Breast Cancer Cells
    Poster: NSF REU Sharon Lin Poster.pdf
    Research Abstract:  Multibranched gold nanoantennas (MGNs), which are gold nanoparticles with multiple sharp protrusions, have been hailed as a potential agent for cancer treatment due to their ability to convert light to heat efficiently for photothermal therapy.  We synthesize MGNs using HEPES, a biological buffer that acts as a capping and reducing agent.   When MGNs are exposed to light at a characteristic wavelength, its surface plasmon resonance (SPR) is achieved, which leads to an enhanced light absorption, allowing for effective light-to-heat conversion.  A concentration of 170 ug of MGNs per ml that is exposed to a laser, at 4 W/cm2 in the near-infrared (IR) region, can produce a temperature increase of up to approximately 53oC.

    We utilize the photothermal characteristics of MGNs to exploit the drug delivery capabilities of liposomes.  We use thermo-sensitive liposomes, which will disassemble when it reaches its transition temperature, which is 42oC.  At this temperature, about 90% of the drug that is encapsulated will be released within the first ten minutes.  The cell line that we use in this project, MDA-MB-231, is normally Doxorubicin-resistant, but once these cells reach the hyperthermia temperature, which is also the transition temperature of the liposomes, they become more susceptible to Doxorubicin.  Because the photothermal characteristics of MGNs can allow liposomes to reach their transition temperature, this combination can be effective in photothermal therapy of breast cancer cells.

  • Jennifer Lomaki - Physics, State University of New York, Geneseo

    Jennifer LomakiEducational Institution: State University of New York, Geneseo
    List of Mentors: Dr. David Cliffel & Aaron Daniel
    Program: NSF TN-SCORE
    Research Project: Electrochemical TNT Detection Utilizing VO2 Particle Films
    Poster: NSF REU Poster Jennifer Lomaki.pdf
    Research Abstract:  Due to its toxic nature, rapid and sensitive detection of TNT is important for groundwater testing, especially near military bases or areas that have been exposed to large quantities of explosive materials.  Previous research has shown that vanadium dioxide (VO2) thin films have the ability to electrochemically detect 2,4,6-trinitrotoluene (TNT) in solution.  VO2 is an interesting material that undergoes a phase transition at 68°C from a semiconducting monoclinic phase (M) to a metallic rutile phase (R).  Limitations of the VO2 thin films include expensive reagents, expensive equipment and low yield.  The hydrothermal synthesis utilized in this project generates a larger yield using inexpensive precursors.  Additionally, doping the material with W6+ allowed for access to the VO2(R) phase at room temperature.  Both VO2(M) and VO2(R) particles were then cast onto a glassy carbon electrode and tested for the ability to detect TNT.  Various polar organic solvents were used to wash the particles and revealed that certain solvents either blocked or enhanced the particles’ ability to detect TNT. 

  • Naomi Mburu - Chemical Engineering, University of Maryland, Baltimore County

    Naomi MburuEducational Institution: University of Maryland, Baltimore County
    List of Mentors: Dr. Leon Bellan & Bradly Baer
    Program: NSF REU
    Research Project: Using 3D Printing to Model Disturbed Flow Through Arteries
    Poster:
    NSF REU Naomi Mburu Poster.pdf
    Research Abstract:  To develop artery-shaped fluidic channels that exhibit both laminar and disturbed fluid flow patterns expected in mouse arteries, we use a 3D printing strategy combined with relevant sacrificial materials. Our goal is to reproduce flow patterns found in mouse arteries in order to increase research speed while reducing cost and the need for animal testing.

    Models of arteries are designed using CAD software and printed on a modified MendelMax2 3D printer using water-soluble polyvinyl alcohol (PVA) filament. The sacrificial templates are then embedded in polydimethylsiloxane (PDMS), and after the PDMS has cured the devices are placed in a water bath to dissolve the PVA, thus leaving hollow channels in the PDMS. We use fluorescent imaging beads to track particle flow through the channels and particle tracking algorithms to analyze flow patterns through these devices. The velocity profiles are used to illustrate areas of laminar and disturbed flow by modeling the devices as tubes and comparing the experimental velocity profiles with expected Newtonian flow patterns. The next step will be to reduce the channel sizes to better emulate the size of an artery in a mouse. After the scaled-down channels have been fully characterized, endothelial cells will be grown on the channel walls of the device to mimic the inside of the artery. Eventually, these devices will be used to test the delivery of drugs targeted to sites of the artery that are prone to plaque buildup due to disturbed flow. The use of such 3D printed vessel models may eventually reduce the need to perform initial experiments on animal models, thus making research on vascular diseases like atherosclerosis more ethical and efficient.

  • Christopher McDonald - Physics, Austin Peay State University

    Christopher McDonaldEducational Institution: Austin Peay State University
    List of Mentors: Dr. Rizia Bardhan & Eric Talbert
    Program: NSF TN-SCORE
    Research Project: Perovskite Layer Optimization of Planar Solar Cells
    Poster: NSF REU Chris McDonald Poster.pdf
    Research Abstract:   Perovskite Solar Cells (PSC’s) are an extremely hot topic in research due to both how new the field is and the amazing growth in efficiency it has shown. This research was to discover an easily repeatable way of creating planar PSC devices that eliminated many of the issues that have currently plagued fabrication such as pin holes and excessive roughness. Our methodology included varying spin coating speeds, anneal temperature and time, and perovskite weight percentage to control layer thickness. To control roughness of the planar layers, which is a function of the crystallization speed, we tested the addition of toluene during spin coating, varied toluene deposition rates and times, and experimented with varying substrate temperature prior to deposition of the perovskite layer. Using profilometer measurements we discovered that the biggest contributing factors for perovskite smoothness were the addition of toluene via a slow drip method during the ramp phase while spin coating at 4000 rpm’s for 60 seconds, and using a 40 wt% solution of perovskite in dimethyl sulfoxide and y-butyrolactone. We then tested our devices using electrochemical impedance spectroscopy to quantify the improvements in efficiency, fill factor, and short circuit and open circuit voltage as a function of perovskite smoothness. This knowledge will help speed along the ability for others to produce reliable and consistent solar cell devices and allow more time and funding to be directed toward improving efficiency and stability.

  • Joshua Ryan Nolen - Physics, Lipscomb University

    Ryan NolenEducational Institution: Lipscomb University
    List of Mentors: Dr. Richard Haglund & Daniel Mayo
    Program: NSF TN-SCORE
    Research Project: ZnO nanowire radiation detectors with high spatiotemporal resolution
    Poster: NSF REU Ryan Nolen Poster.pdf
    Research Abstract: Zinc oxide nanowires are potentially useful photoluminescent (PL) radiation detectors, because both the ultraviolet (near band-edge) and visible (donor-acceptor pair defect) emission are altered by ionizing radiation.  Zinc oxide in thin film and nanopowder form has been studied for use as a scintillator, but the omnidirectional optical response is relatively weak for finite detector solid angles.  However, zinc oxide nanowires can be grown to emit in a single direction through waveguiding effects, therefore making PL detection highly efficient.  We have measured the PL response of zinc oxide nanowires to gamma rays (662 keV) and quantified the effects of nanowire surfaces and interfaces on the PL response.  By studying the PL kinetics as a function of time following irradiation, we infer the relaxation rates of specific radiation-induced defects, including oxygen vacancies.

  • Uchechukwu Uc Obiako - Chemical Engineering, Cleveland State University

    Uc ObiakoEducational Institution: Cleveland State University
    List of Mentors: Dr. David Cliffel & Evan Gizzie
    Program: NSF REU
    Research Project: Enhancement of Solar Energy Conversion in Bio-derived Cells via Side Selective Modification of Photosystem I
    Poster: NSF REU Uc Obiako Poster .pdf
    Research Abstract:  Deleterious effects of some methods used to harness energy from the environment today have garnered the exploration of safer and more reliable options, specifically solar energy conversion. Current solar cell technology has yielded quantum efficiencies commonly in the range of 10-20% but is limited by extensive processing methods, high cost, and need for rare materials. However, bio-derived solar cells containing Photosystem I (PSI) address these problems as PSI is highly abundant, very efficient, and low-cost. PSI acts as a biomolecular photodiode through rapid photoexcited charge separation, making it very promising for use as an integral element in solar cells. To further improve the efficiency of bio-derived cells, controlling the orientation of PSI films on gold substrates was explored. This was achieved by side-selectively modifying PSI to introduce terminal thiol groups to the protein complex thereby providing a vector of self-assembly onto the gold surface. Spinach thylakoid membranes containing PSI were extracted and chemically modified using the ligands: sulfo-N-succinimidyl S-acetylthioacetate and 2-iminothiolane. As a result, the functionalized PSI underwent direct surface coupling on gold electrodes in an inverted orientation. Fluorescence tagging was used to quantify ligand attachment to PSI. Additionally, photoelectrochemical analysis revealed an enhancement in photocurrent produced by the modified biohybrid electrodes.

2014

  • Nastasia Allred - Chemical Engineering, Tennessee Technological University

    Nastasia AllredEducational Institution: Tennessee Technological University
    List of Mentors: Dr. Rizia Bardhan & Will Erwin
    Program: NSF TN-SCORE
    Research Project: Plasmon Enhanced Tandem Dye-Sensitized Solar Cells
    Poster: NSF REU Nastasia Allred Poster.pdf
    Research Abstract:  
    Our current energy economy faces environmental concerns, as well as concerns of lacking availability of fossil fuels. In 2013, roughly 80% of energy consumption in the U.S. was achieved through fossil fuels, while only 0.3% of the energy consumed was produced by solar resources.1 Dye sensitized solar cells (DSSCs) show promise because they are less expensive and made of more easily recyclable, less hazardous materials than silicon photovoltaics (Si-PVs); however, one of the major problems with DSSCs is that they do not reach high enough efficiencies to compare to Si-PVs. In this work, two approaches to enhancing DSSC efficiency are complementary to each other; i) making a tandem DSSC with two types of sensitizing dye and ii) by incorporating tunable plasmonic particles into the devices. Each DSSC has a mesoporous TiO2 layer onto which an organic dye is adsorbed. In this study, the tandem DSSCs consist of cells using N719 (red) and N749 (black) dyes. The cells are arranged such that the light source strikes the cell containing the N719 dye first. This is such that the light not absorbed by the red dye now has the chance to be absorbed by the black dye, thus increasing the cell’s light harvesting capabilities. Plasmon enhancement is accomplished by incorporating broad resonance Au@Ag bimetallic nanoparticles into the mesoporous semiconductor layer, thereby increasing the scattered light and overall photocurrent of the device.

  • Efrem Beraki - Eletrical Engineering, Georgia Institute of Technology

    Efrem BerakiEducational Institution: Georgia Institute of Technology
    List of Mentors: Dr. Sharon Weiss & Yiliang Zhao
    Program: NSF REU
    Research Project: Kinetic Analysis of Porous Silicon Biosensors
    Poster: NSF REU Efrem Beraki.pdf
    Research Abstract:   
    This research investigates the molecular binding kinetics and detection sensitivity differences between mesoporous optical biosensors of closed-end porous films and open-ended, flow-through membranes. A porous silicon material system is employed due to its many advantages for biosensing applications, including a large active sensor surface area and tunable porosity and pore size, as well as it amenability to standard silicon lithographic processing techniques. Size-selective sensing and relatively high detection sensitivities have already been demonstrated in closed-end porous silicon biosensors. Here, we describe the fabrication process to realize porous silicon membrane sensors, which is based on photolithographic patterning and reactive ion etching of a silicon wafer followed by selective electrochemical etching to form the porous silicon regions. We then seek to characterize and compare the performance of closed-end and membrane style porous silicon sensors. The binding kinetics of the porous silicon sensors were evaluated by flowing different molecules through a flow-cell attached to each sensor and monitoring the change in the Fabry-Perot interference pattern as a function of time and flow rate.  A comparison of the detection sensitivity of closed-end and membrane sensors can be made by evaluating the rate of change of the interference pattern, as well as the saturation time for which all available binding sites are occupied. This work is expected to lead to the realization of lab-on-chip compatible porous silicon membrane sensor arrays capable of fast response, high sensitivity, and simultaneous detection of multiple analytes.

  • Matthew Billingsley - Chemical Engineering, Rose-Hulman Institute of Technology

    Matthew BillingslyEducational Institution: Rose-Hulman Institute of Technology
    List of Mentors: Dr. Peter Cummings & Andrew Summers
    Program: NSF REU
    Research Project: Investigating Wear Mechanisms of Alkylsilane Monolayers through Molecular Dynamics Simulation
    Poster: NSF REU Matthew Billingsly Poster.pdf
    Research Abstract:  
    Alkylsilane monolayers have been proposed as lubricants for microelectromechanical and nanoelectromechanical systems (MEMS and NEMS), having been shown to reduce friction and wear and protect surfaces from oxidation. However, these monolayers are known to degrade over time, whereby chains break off of the surface. In this study, we utilize molecular dynamics (MD) simulations to study the frictional properties of hexylsilane monolayers attached to silica substrates, focusing on the effects of monolayer wear. Wear is introduced in a controlled manner by randomly detaching a specified fraction of chains from each substrate. Frictional properties and free-chain mobility (i.e., broken chains) are investigated as function of induced monolayer wear. For crystalline silica substrates, we find that normal load has a negligible effect on the mobility of free chains; mobility is instead correlated with the fraction of broken chains. Amorphous systems reveal a higher degree of free-chain mobility compared to crystalline systems with identical levels of induced wear, which we correlate to the increased surface roughness of the amorphous substrates. Furthermore, systems with amorphous substrates have higher coefficients of friction (COF), suggesting an inclination toward increased wear at all conditions.

  • Elijah Brown - Electrical Engineering, Austin Peay State University

    Educational Institution: Austin Peay State University
    List of Mentors: Dr. Kirill Bolotin & Alex Wynn
    Program: NSF TN-SCORE
    Research Project: Nano-capacitors: Investigating Electrical Fields between Different 2-Dimensional Materials

    Research Abstract:
    Graphene is one of the most diverse and exciting materials currently being investigated by researchers. Graphene is known as a 2-Dimensional material, it is called this because electrons are only moving through the material in two dimensions. 2-Dimensional materials are observed as a one to three atom thick substance typically called a mono-layer. There are many other materials available to researchers that can produce mono-layers besides Graphene, such as molybdenum disulfide, tungsten disulfide, and niobium diselenide among others. Artificially creating new materials by stacking mono-layered substances such as these is becoming commonplace. When Graphene is stacked with some materials, such as the forementioned ones, researchers have witnessed the effects of sending an electric current through them, an electrical field begins to form in the gap between them. Generally researchers have taken for granted that the electrical field building up between these layers is due to the mechanics of charge transfer. However, there have been several other plausible speculations that could possibly explain this event; such as the suggestion of a characteristic called FRET (florescence resonance energy transfer). To allow for the testing of this hypothesis measurable devices will have to be fabricated. Capacitors are a commonly used component of analog electronic circuits. Capacitors are made using two electrically conductive plates separated by a small gap, as voltage is pushed through the plates over time an electrical field will build up between them. Since the stacked mono-layers behave like capacitors, it is possible to put them through the same physics tests as capacitors, and should prove or disprove that charge transfer is responsible for the phenomenon.

  • Kathryn Bumila - Chemical Engineering, Worcester Polytechnic Institute

    Katie BumilaEducational Institution: Worcester Polytechnic Institute
    List of Mentors: Dr. John Wilson & Max Jacobson
    Program: NSF REU
    Research Project: Developing New Amphiphilic Diblock Co-Polymers for Delivery of Cytosolicly Active Immunostimulants
    Poster: NSF REU Katie Bumila Poster.pdf
    Research Abstract:   
    A major barrier to synthetic vaccine development is inefficient delivery of immunostimulatory adjuvant molecules to the cytosol of antigen presenting cells. In order to overcome this challenge, we are developing pH-responsive diblock copolymers that can be utilized as nano-carriers for these adjuvants. A successful nano-carrier must form stable micelles under physiological conditions as well as have endosomal escape capabilities to promote delivery to cytosolic pathogen recognition receptors. A library of amphiphilic diblock copolymers was synthesized in order to compare the effect of the hydrophobic group on nanoparticle properties and drug delivery qualities. The hydrophobic groups compared were butyl methacrylate (BMA) and hexyl methacrylate (HMA), as components of [poly(ethylene glycol)]-block-[2-dimethylaminoethyl methacrylate-co-BMA] and [poly(ethylene glycol)]-block-2-[dimethylaminoethyl methacrylate-co-HMA] polymers, respectively. The second blocks were designed to have compositions of 20%, 30%, and 40% BMA or HMA. To determine the polymer’s ability to form micelles, dynamic light scattering was performed over a range of pH 5.8-7.4. This experiment showed that the polymer containing 30% HMA, 40% HMA, and 40% BMA successfully formed 13-18 nm diameter micelles at pH 7.4 and transitioned to unimeric polymer chains with decreasing pH. Next, a hemolysis assay was performed across the same pH range. The results showed that 40% BMA displayed the greatest membrane disruptive characteristics at pH 5.8 and pH 6.2, however, at most pH values 20% HMA and 30% HMA were significantly more hemolytic than their BMA counterpart. Lastly, a cell viability assay was carried out to determine if any of the polymers were harmful to cells. The results showed an average of 80% or higher cell viability at concentrations ranging from 0.01-10 μg/ml, with the 40% HMA polymer appearing the least cytotoxic. In conclusion, initial results suggest that PEG-bl-DMAEMA-co-BMA and PEG-bl-DMAEMA-co-HMA are promising cytosolically active nano-carriers. However, the novel HMA containing polymers could prove to be even more efficacious for this application because of the increased membrane destabilizing activity and particle stability associated with longer hydrophobic chains. 

    • Katie presented her summer research poster at the 2014 American Institute of Chemical Engineers Annual Meeting in Atlanta, GA.
  • Ashton Davis - Mathematics, LyMoyne-Owen College

    Ashton DavisEducational Institution: LeMoyne-Owen College
    List of Mentors: Dr. Cary Pint & Andrew Westover
    Program: NSF TN-SCORE
    Research Project: Remote Charging for Light Integrated Energy Storage Systems via Lasers
    Poster: NSF REU Ashton Davis Poster.pdf
    Research Abstract:
    As we move into the future, finding new methods of obtaining energy has become a priority of research. Solar Panels have proven to be an efficient means of converting energy from sunlight to electricity and super capacitors have proven to be one of the most efficient energy storage systems for our future. This project is focused on combining both of these technologies in order to have an energy storage device that can obtain a charge remotely with a supercapacitor integrated on the back of the solar cell. One potential method of remotely charging these integrated energy storage devices is through the use of LASERS. LASERS give a form of transmissible energy that can be used at any time. One of the great advantages of lasers is their high wall plug efficiency allowing for efficient energy in addition to its remote capabilities Not only do lasers have great energy efficiencies, but they can be used distances farther than kilometers away and being paired with a supercapacitor, the device can be charged rapidly. This technology will allow for high efficiency remote charging of a variety of energy storage devices ranging from UAVs, household electronics, robotics etc. The research and findings of this project are promising to greatly improving everyday energy usage.

  • Elizabeth Delesky - Materials Science & Engineering, University of Florida

    Elizabeth DeleskyEducational Institution: University of Florida
    List of Mentors: Dr. Eva Harth & Kelly Gilmore
    Program: NSF REU
    Research Project: Biodegradable Polyester Hydrogels for Sustained Drug Delivery
    Poster: NSF REU Elizabeth Delesky Poster.pdf
    Research Abstract:   
    Hydrogels have recently emerged as promising materials for drug delivery applications for both synthetic and biological cargo. However, many of the current systems are limited due to the non-degradable nature of the gels. Polyester hydrogels synthesized using oxime click chemistry are an attractive option as drug delivery vehicles due to their biocompatibility and degradability. In this study, we have utilized a copolymer comprised of δ-valerolactone and 2-oxepane-1,5-dione as well as an amino-oxy functionalized polyglycidol to synthesize these gels. Hydrogels were synthesized using three different ratios of the two reactants in order to tune the swelling and degradation profiles. The swelling profiles revealed that maximum swelling occurs within the first few hours.  Swelling was observed after degradation began as the ester linkages were hydrolyzed, which allowed water to infiltrate the gels and increase the mass as the gels degraded.  Both the swelling and degradation profiles revealed that increasing the amount of cross-linker prevents rapid degradation of the hydrogel. The free drug release rate of these hydrogels was also studied, using brimonidine as a model drug, as well as release rates incorporating the drug into an additional complex, such as β-cyclodextrin. β-cyclodextrin can be homogeneously dispersed through the hydrogel to provide an ancillary boundary for the drug and prolong the release.

  • Amadou Fall - Chemistry, Tennessee State University

    Amadou FallEducational Institution: Tennessee State University
    List of Mentors: Dr. Janet Macdonald  & Andrew LaCroix
    Program: NSF TN-SCORE
    Research Project: Investigating the electronic coupling of quantum dot-ligand interaction
    Poster: NSF REU Amadou Fall Poster.pdf
    Research Abstract:  
    Photocatalysis and the use of solar cells are having an ever increasing importance in our search for renewable energies. Quantum dots, which are nanoscale particles of semiconductors (in our case Cadmium selenide), are a driving force in this endeavor. Reasons for this include that they are inexpensive to make, have a strong molar absorptivity, and are easily tunable to the desired size.  The synthetic methods used to obtain monodisperse samples of different sizes require charge transfer inhibiting organic ligands. The Macdonald group has discovered a crystal-bound ligand system that can increase nanoparticle stability and charge transfer efficiency. We optimized the synthesis of CdSe@ZnS core-shell nanoparticles to increase the quantum yield. Hydrolysis of the ester group in dodecyl-3-mercaptopropionate-capped CdSe@ZnS core-shell nanoparticles results in a red shift in absorbance and fluorescence, which could be due to energetic overlap of the carboxylate ligand and the CdSe@ZnS core-shell nanoparticle. In this project we plan to compare the results of our seed, shelling, and hydrolysis with the Brus quantum confinement equation to determine if the observed electronic interaction is with the valence or conduction band. We can use the results of the data to design better and more efficient photocatalytic and photovoltaic devices.  

  • Nicholas Morgan - Chemical Engineering, University of Oklahoma

    Nicholas MorganEducational Institution: University of Oklahoma
    List of Mentors: Dr. Peter Pintauro & Devon Powers
    Program: NSF REU
    Research Project: Optimizing the Fabrication of Solution-Cast Membranes
    Poster: NSF REU Nicholas Morgan Poster.pdf
    Research Abstract:   
    As the current fossil fuel-based economy continues to present environmental challenges and issues of sustainability, the fuel cell shows promise to be a highly efficient source of clean energy in the near future. Integral to the operation of a fuel cell is the membrane, which separates the cathode and the anode and provides pathways for proton transport. For efficient operation, the membrane must exhibit high proton conductivity, robust mechanical strength, and low fuel crossover. The most common proton transport material used is perfluorosulfonic acid (PFSA) polymer, sold by DuPont under the name Nafion. This material exhibits high conductivities but also relatively high crossover rates for many fuel and oxidants used in fuel cells such as methanol or bromine species, leading to the degradation of catalysts at the electrodes. Additionally, Nafion’s poor mechanical strength poses a problem due to excessive swelling during each on/off cycle. To make up for these deficiencies, Nafion can be mixed with an inert reinforcing polymer such as polyvinylidene fluoride (PVdF), resulting in a favorable reduction in swelling and fuel crossover but also a loss of conductivity. In the present study, Nafion-PVdF membranes were fabricated by solvent casting, where a solution containing the two polymers is spread on a glass plate to form a film that is dried in an oven, producing a 50-100 μm-thick membrane. We investigate the effect of using N,N-dimethylacetamide, N,N-dimethylformamide, and N-methyl-2-pyrrolidone as casting solvents and the effect of varying annealing times and temperatures on the conductivity, water uptake, and swelling properties of these blended membranes. We also vary the Nafion-to-PVdF ratio for each solvent to map the ranges over which the most successful solvent-annealing combination can be applied. Results indicate that the annealing condition that yields the highest conductivity is not solely a function of solvent but of both solvent and proportion of Nafion, with membranes containing the highest and lowest proportions of Nafion showing sensitivity to higher annealing temperatures and subsequent losses in conductivity. Phase separation is observed to consistently lead to a loss in conductivity as well. Water uptake and swelling properties appear to be constant and largely independent of solvent and annealing conditions. Future work will include testing additional combinations of solvents, annealing conditions, and Nafion proportions in order to draw further conclusions about the interactions of these parameters, as well as examining fuel crossover and tensile strength.

  • David Needell - Math & Physics, Bowdoin College

    David NeedellEducational Institution: Bowdoin College
    List of Mentors: Dr. David Cliffel & Gabriel LeBlanc
    Program: NSF REU
    Research Project: Biohybrid Solid State Solar Cells
    Poster: NSF REU David Needell Poster.pdf
    Research Abstract: 
    While traditional p-n junction photovoltaic panels continue to be the most popular solar cell currently available, the cost of processing and constructing these cells have limited their dissemination into the energy market.  For this, alternative solar cells constructed from organic and easier to obtain materials aim to be one solution to this problem.  Photosystem I (PSI) is an essential part of the photosynthetic process present in green plant cells and cyanobacteria – a protein responsible for exciting a free electron given an incident photon. PSI’s abundance in nature and nearly perfect quantum efficiency make PSI a prime candidate for use in solar cells. 

    The ultimate aim of this research is to determine if a biohybrid, solid-state solar cell – constructed from inexpensive conductive substrates – can generate electrical power.  Conductive and transparent Reduced Graphene Oxide (rGO) and Poly(3,4-ethylenedioxythiophene) Polystyrene sulfonate (PEDOT:PSS) served as the counter and working electrode in the solid-state cell, respectively. Current-voltage analyses and photochronoamperometry tests show that both rGO and PEDOT:PSS can be successfully incorporated into a fully functional, solid-state biohybrid cell with a doped semiconducting substrate.  This information gives strong support to the construction of a working, metal free, and biohybrid solid-state solar cell with rGO, PSI, and PEDOT:PSS.  Future work includes refining the technique of constructing this metal free, flexible solar cell and improving the orientation alignment of the multilayered PSI film.  

  • Jason Ray Alfaro - Physics, Juanita College

    Jason Ray AlfaroEducational Institution: Juanita College
    List of Mentors: Dr. Qi Zhang & Kristina Kitko
    Program: NSF REU
    Research Project: Effects of Cholesterol Enhancement on Cell Properties in the Presence of Graphene
    Poster: NSF REU Jason Ray Alfaro Poster.pdf
    Research Abstract:   
    Graphene is a two-dimensional carbon crystal with remarkable mechanical strength and a singular electrical conductivity, a combination that has led to surging interest in its biomedical applications. However, this demands a clear understanding of graphene’s interaction with cell surface molecules and its impact on cell function. Here,  based upon the observed increase of synaptic surface cholesterol in cells directly growing on bare graphene, we propose that graphene interacts with cholesterol. This increase changes the amount, the release probability, the turnover mode and the reuse rate of synaptic vesicles, which results in a presynaptic potentiation of neurotransmission. Further spectral analysis of fluorophore interaction with graphene reveals a time-dependent fluorescence decay that is unique from that of the fluorophore, consistent with the interaction involving energy transfer. Assaying for the cholesterol concentration of culture media in the presence of graphene may provide direct insight into this interaction. These data may be further supported by an increase in the membrane resistance in the presence of graphene, although additional verification is necessary. Our findings highlight a molecular mechanism underlying graphene's effect on the lipid membrane and cell signaling, which infers caution as well as opportunity in basic research and translational implementation of graphene. 

  • Jesús Sosa-Rivera - Biotechnology, Universidad del Este

    Jesus Sosa-RiveraEducational Institution: Universidad del Este
    List of Mentors: Dr. Craig Duvall
    Program: NSF REU
    Research Project: Localized Delivery of a Chemotherapeutic from Cell-Degradable Polymeric Films
    Poster: NSF REU Jesus Sosa-Rivera Poster.pdf
    Research Abstract:  
    Cancer is the second leading cause of death worldwide. In gastric cancer, most patients are treated by tumor resection in the early progression stages. However, recurrence of cancer at the margin of resection can occur in 50% of cases.  Secondary, more systemic treatments like chemotherapy and external radiation are the current gold-standard treatments for inhibiting cancer recurrence but produce systematic totoxicities that can severely limit the long term survival of the patient. To limit these systemic toxicities, we hypothesize that prolonged, localized drug delivery at the tumor resection margins will prevent cancer cells proliferation and tumor recurrence. Here, we propose to incorporate a hydrophobic, anti-neoplasmic drug into a hydrophobic, acidically-inert, polymeric film to achieve prolonged drug release and sustained inhibition of cancer cell proliferation in the harsh environment of the stomach. These films were made with poly(thioketal) (PTK) polymers, which are both stable across a wide range of pH values and are specifically degraded by cell-produced reactive oxygen species (ROS). The PTK polymers, synthesized from biocompatible mercaptoethyl ether (MEE) monomers, were rigorously characterized and then incorporated into films by solvent casting with a non-degradable hexamethylene diisocyante trimer (HDIt). The PTK-UR films were loaded with either Nile Red (fluorescent hydrophobic model drug) or the strong anti-tumor hydrophobic drug 10-hydroxycamptothecin (HCPT), which has seen limited clinical use due to its poor aqueous solubility but has great potential as a locally delivered chemotherapeutic (Wolinsky, JB. et al 2010). In preliminary studies, Nile Red-loaded PTK-UR films demonstrate gradual, sustained levels of drug release when incubated in an ROS-producing medium, while demonstrating minimal drug release when incubated in saline. Ongoing studies are evaluating the cytotoxic activity of released HCPT and drug release under stomach-mimicking acidic conditions, while futures studies will evaluate the sustained cytotoxic effect of released HCPT both in vitro and in vivo.

    • Jesus presented his summer research poster at the 2014 Annual Biomedical Research Conference for Minority Students in San Antonio, TX (won ABRCMS award).
  • Lucas Thal - Biochemistry, University of Tennessee, Knoxville

    Louis ThalEducational Institution: University of Tennessee, Knoxville
    List of Mentors: Dr. David Cliffel & Gabriel LeBlanc
    Program: NSF TN-SCORE
    Research Project: A New Method for Improving Solar Energy Conversion: Side Selective Modification of Photosystem I
    Poster: NSF REU Poster Louie Thal.pdf
    Research Abstract:  
    Adverse environmental impacts caused by traditional methods for harnessing energy have prompted the search for clean renewable energy. Recently, solar power has been at the forefront of researchers’ investigations for viable new, sustainable sources of energy. Solar cell devices on the market convert solar radiation to electricity at around 10-20% efficiency. They are constructed with inorganic materials (e.g. silicon, indium, and tellurium) that are resource- and cost-limiting. Alternatively, biohybrid cells produce photocurrent when integrated with the plant protein Photosystem I (PSI)—a sterically stable transmembrane redox protein found in light-dependent photosynthesis. This approach offers extremely efficient solar conversion (approaching 100% at specific wavelengths) without resource depletion. Given that the charge separation that occurs in is unidirectional with regard to PSI’s molecular orientation, the protein must be oriented on electrodes such that the P700 chlorophylls are aligned away from the electrode. Visual inspection of the crystal structure of the protein extracted from spinach (PDB ID: 2WSF), reveals that the hydrophilic areas are similar in both basic and acidic acid compositions.  This similarity allows for the protein to bind to electrodes in both upright (P700 distal from the electrode) and inverted orientations. Previous research has shown that increasing the fraction of upright oriented proteins on electrode in turn increases photocurrent produced [1]. We can accomplish this by modifying the chemical properties of the hydrophilic regions to promote surface asymmetry so that the stromal/luminal sides of the protein have different affinities for the underlying electrode. Side-selective functionalization of extracted PSI was performed by pre-extraction EDC/Sulfo-NHS coupling to glutamic and aspartic acids with thiol terminated adducts on the stromal side of the thylakoid. We have shown that the functionalization was successful by performing - UV-vis and fluorescence spectroscopic analysis. We have also developed a chromatographic purification procedure that would potentially remove the unmodified proteins from the bulk sample. Currently, we are performing electrochemical analysis on the effectiveness of the functionalized samples.  Further optimization of this method will create a new library of ligands to adjoin allowing for many new biomolecular applications.

    • Louie presented his summer research poster at the 2014 66th Annual Southeastern Regional Meeting for the American Chemical Society in Nashville, TN and is scheduled to present his poster at the 249th American Chemical Society National Meeting and Exposition in March 2015.
  • Holly Thomas - Mechanical Engineering, St. Ambrose University

    Holly ThomasEducational Institution: St. Ambrose University
    List of Mentors: Dr. Melissa Skala & Jason Swartz-Tucker
    Program: NSF REU
    Research Project: Metabolic Imaging of Human Breast Carcinoma Treatments
    Poster: NSF REU Holly Thomas Poster.pdf
    Research Abstract:  
    Human breast carcinoma is known to dramatically alter cellular metabolism. Rather than generating ATP through oxidative phosphorylation, cancerous cells utilize aerobic glycolysis, which requires an increase in glucose consumption. Current autofluorescence imaging techniques, particularly two-photon microscopy, are capable of detecting changes in cellular metabolism by quantifying biological markers of cellular metabolic rate. These markers include the autofluorescent metabolic co-enzymes NADH and FAD, and two-photon microscopy is used to measure their fluorescence lifetimes and relative intensities (redox ratio). These measurements reflect enzyme activity and relative rates of cellular glycolysis, respectively. However, redox ratio and lifetime analysis neglects the possible effects of glucose uptake and mild hyperthermia in breast cancer cells. To measure glucose uptake in breast cancer cells, cells were incubated with the fluorescent glucose molecule 2-NBDG and imaged at the NADH and 2-NBDG emission wavelengths using two-photon microscopy. Additionally, cells were treated with the anticancer drugs trastuzumab, paclitaxel, and XL147 to investigate their effects on 2-NBDG uptake. The findings demonstrated a significant (p<0.05) decrease in 2-NBDG fluorescence in cells treated with anticancer drugs from those that were left untreated. Furthermore, treated and untreated breast cancer cells were incubated with iron oxide-coated gold nanorods and imaged at the NADH, FAD, and nanoparticle emission wavelengths to determine whether the presence of gold nanorods altered cellular metabolism. Controlled photothermal heating of nanorods in distilled water verified that the nanorods are capable of being heated, yet two-photon imaging indicated that the nanorods were not functionalized properly for in vitro applications. Further work must be done to properly functionalize the nanorods and image them in vitro to measure variations in cellular metabolism. 2-NBDG fluorescence imaging will likely be expanded to measure glucose uptake in three-dimensional organoids with the goal of implementing these measurements to determine the most beneficial treatment for breast cancer patients on an individual basis.

  • Vincent Viola - Physics, Rhodes College

    Vincent ViolaEducational Institution: Rhodes College
    List of Mentors: Dr. Peter Pintauro & Jun Woo Park
    Program: NSF TN-SCORE
    Research Project: Solvent Effects on Single-Fiber Electrospinning and Membrane Properties
    Poster: NSF REU Vincent Viola Poster.pdf
    Research Abstract:   
    Fuel cells utilize redox chemistry to convert chemical energy of various fuels, for example hydrogen, into electrical energy.  They provide environmentally friendly alternative to conventional energy conversion devices, like internal combustion engines, that use fossil fuels. However, currently available fuel cells still require optimization to improve their performance and lifetime. The key areas of interest are more durable and cheaper catalysts and better membranes.  This study focuses on novel proton conducting membranes fabricated using single-fiber electrospinning of Nafion-PVDF (polyvinylidene fluoride) blends. Here, a solution of Nafion and PVDF mixture is electrospun onto a rotating and oscillating aluminum target forming a porous mat of thickness 120-200 μm. The mat is then annealed at elevated temperture (150-210oC) and hotpressed at 182oC and 24000lb, to close the pores and create dense, defect free proton conducting membrane. Finally, the membrane is preconditioned in boiling 1M H2SO4 and then boiling water.  The goal of this study is to understand the effect of electrospinning solvent, composition and post-processing conditions on the membrane proton conductivity, water uptake and swelling. The conductivity was measured using four-electrode Bekktech cell. Water uptake was measured gravimetrically and areal swelling was determined by comparing membrane’s dry and wet dimensions.   The most desired characteristics were obtained for membranes electrospun from 80% Nafion and 20% PVDF, pre-compacted and annealed at 150oC for 1.5 hours under vacuum. The obtained conductivity was in the range 0.066-0.070 S/cm, the gravimetric swelling was in the range 12.91-13.74% mg/mg, and the areal swelling was in the range 15.59159681-17.98638329% mm2/mm2.   Selected membranes will later be tested in hydrogen, direct methanol and hydrogen-bromine fuel cells.

  • Patrick Wellborn - Chemistry & Engineering, Washington & Lee University

    Patrick WellbornEducational Institution: Washington and Lee University
    List of Mentors: Dr. Kane Jennings & Max Robinson
    Program: NSF REU
    Research Project: Bridging the Gap: Photosystem I Initiated Polymer Growth for Solid-State Solar Cell Applications
    Poster: NSF REU Patrick Wellborn Poster.pdf
    Research Abstract:  
    Photosystem I (PSI) is a photocatalytic membrane protein contained within the thylakoid membranes of plants.  Boasting ~1 V light-induced charge-separation and near-unity quantum yield, PSI has garnered interest as a photoactive species in next generation biohybrid solar cell devices.  Order-of-magnitude improvements in generated photocurrents have been observed for PSI-integrated systems utilizing a liquid electrolyte mediator to transport photoexcited electrons from PSI to the anode.  However, practical devices of this sort introduce problems of degradation and expense. Solid-state devices eliminate the need for liquid mediation, shuttling photoexcited electrons directly using solid conductive materials, creating a more durable device.

    This study explores a PSI-initiated polymerization technique, providing a route to more efficient PSI-PSI electron transport within the active layer of solid-state devices.  Incident amino acid residues from PSI are used as initiators for Surface-Initiated Ring-Opening Metathesis Polymerization (SI-ROMP). A fluoro-alkyl substituted norbornene monomer—characterized by fast growth kinetics and a unique spectroscopic signature—was chosen for preliminary studies. Polarization-Modulation Infrared Reflection Absorption Spectroscopy (PMIRAS) and three-electrode photochronoamperometry were used to establish retained secondary structure and photoactivity during each step of the polymerization process.

    Two methods of polymer attachment were utilized on PSI monolayers and multilayers: lysine-based attachment using amine termini and glutamic and aspartic acid-based attachment using carboxylic acid termini. Both methods proved successful for polymer growth, achieving ~10nm of growth on monolayers and hundreds of nanometers of growth on PSI multilayers. Results of polymer growth were characterized using goniometry, ellipsometry, profilometry, and IR. With no previous literature indicating polymer growth on proteins via SI-ROMP, this study acts as a proof-of-concept with promising results. Future work entails the synthesis of an anchored polythiophene (PT) monomer to a norbornene backbone, providing for a covalently-wired and highly conjugated polymer matrix for efficient PSI-PSI charge mediation. 

  • Anna Yanchenko - Physics & Math, University of Virginia

    Anna YanchenkoEducational Institution: University of Virginia
    List of Mentors: Dr. Richard Haglund & Rod Davidson
    Program: NSF REU
    Research Project: Electric-Field-Induced Second-Harmonic Generation in Asymmetric Nanogaps
    Poster: NSF REU Anna Yanchenko Poster .pdf
    Research Abstract:  
    Asymmetric plasmonic nanoparticles can be used to generate and control the spatial distribution of electric fields at the nanoscale in order to efficiently generate second-harmonic light and control its polarization response. Electric-field-induced second-harmonic generation (EFISH) allows for the optical modulation of second-harmonic light using an external, applied electric field.  Previous work has shown modulation of EFISH signals using DC electric fields in plasmonic grating geometries. (Brongersma, Science 2011) The governing mechanism in second-harmonic generation is a second order, nonlinear process controlled by a tensor, χ(2), which vanishes under central symmetry.  In our experiments, we fabricated novel asymmetric gold nanogaps and demonstrated that they produced second-harmonic light with a conversion efficiency on the order of 10-11.  Three plasmonic geometries were fabricated to create unique electric field gradients on a length scale of the order of 100nm.  Finite-difference time-domain (FDTD) simulations and experimental extinction spectra of the nanogaps were performed, and the nanogaps were found to have broad plasmonic resonances at 800 nm.  The plasmons were excited with a horizontally polarized ultrafast Ti:Sapphire laser at 800nm and a spatial light modulator was used to compress these pulses to ~20fs. The SHG efficiency resulting from this plasmon excitation was measured as a function of power.  PMMA was then deposited into the nanogaps, and we found that the PMMA red-shifted the plasmon resonance and reduced the SHG conversion efficiency due to absorption by the PMMA.  Future experiments are planned with additional centrosymmetric materials, such as Si, Si3N4, and SiO2, non-centrosymmetric materials, like GaAs, and ferroelectric materials, such as BaTiO3.  Additionally, the relation between the polarization of the incoming pulse and the produced SHG will be explored and further experiments are planned to pump the gold nanogaps with a different frequency of light (1053 nm), with potential applications for optical switching.

2013

  • Christopher Armenia - Chemistry, Villanova University

    Christopher ArmeniaEducational Institution: Villanova University
    List of Mentors: Dr. Eva Harth & Dan Beezer
    Program: NSF REU
    Research Project: Derivatization of Polyglycidol and the Synthesis of Hydrogels by Oxime Click Chemistry
    Poster: NSF REU Christopher Armenia Poster.pdf
    Research Abstract:
    A hydrogel is a network of hydrophilic polymers that has the ability to absorb water. These gels have similar properties to human organs and tissues, and thus have many medical applications, such as drug transport and gene therapy. These hydrogels can act as a matrix to which biomedical nanoparticles can be attached and allow drugs to be more effectively delivered throughout the human body. This project focused on the synthesis of polyglycidol hydrogels by functionalizing polyglycidol polymers and reacting these various derivatives with each other. Three different polyglycidols were synthesized: amino-oxy polyglycidol, 3-mercaptopropanoyl polyglycidol, and 4-pentenoyl polyglycidol. In order to characterize the properties of the derivatives that were synthesized, model reactions were conducted using 3-ethoxy-1,2-propanediol because it has similar functional groups to polyglycidol. Using click reactions, three hydrogels were synthesized: the first was composed of 3-mercaptopropanoyl polyglycidol and 4-pentenoyl polyglycidol, the second was composed of 4-pentenoyl polyglycidol and 3,6-dioxa-1,8-octanedithiol which acted as a linker between the polymers, and the third was composed of the amino-oxy polyglycidol and a previously synthesized polymer of o-phenylenediamine and valerolactone. These gels are further characterized of their functionalities and physical properties.

  • Megan Burcham - Engineering, University of Tennessee, Martin

    Megan BurchamEducational Institution: University of Tennessee, Martin
    List of Mentors: Dr. Peter Pintauro & Ethan Self
    Program: NSF TN-SCORE
    Research Project: Influence of Polymer Binder Properties on the Performance of Si-Based Anodes for Li-ion Batteries
    Poster: NSF REU Megan Burcham Poster.pdf
    Research Abstract:
    Since their 1990 market debut by Sony, Li-ion batteries (LIBs) have become a popular energy storage platform for portable electronic devices. Electric vehicles powered by LIBs have also experienced recent successes, but they are currently limited to short range commutes due to the low capacity of electrode materials. Silicon is a promising candidate for next generation LIB anodes due to its high theoretical capacity (3,576 mAh/g), which is an order of magnitude greater than that of graphite (372 mAh/g) used today in commercial battery anodes. Industrial adaptation of Si anodes, however, has been hindered by complications arising from Si volumetric changes (~400%) during battery charging and discharging. These volumetric swings ultimately lead to poor capacity retention resulting from Si electronic isolation and an unstable solid-electrolyte interface. In this study, a number of polymers —poly(acrylic acid), carboxymethyl cellulose, poly(vinyl butyral-co-vinyl alcohol-co-vinyl acetate), and poly(vinylidene fluoride)—were investigated as potential binders to accommodate Si swelling without compromising the overall electrode integrity. The selected polymers contained different functional groups to better understand the effects of Si-binder and binder-electrolyte interactions on anode stability. Thermally induced polymer crosslinking was also examined as a way to house Si volume changes without disrupting the electronic conductivity network. Composite anodes containing Si nanoparticles and conductive carbon powder embedded in a polymeric binder were characterized in Li-ion half-cells where anode performance was evaluated by means of cyclic charge/discharge experiments. These composite anodes exhibited outstanding initial capacities, exceeding 1,000 mAh/g. Moderately stable anodes were obtained using binders that (i) participated in hydrogen bonding with the Si-O surface layer on the Si nanoparticles and (ii) exhibited low swelling in the battery electrolyte. Crosslinking the polymeric binders did not further enhance capacity retention. These findings will be used as reference data for future studies that will focus on silane surface modified Si nanoparticles.

  • Emily Darby - Chemistry, Pomona College

    Emily DarbyEducational Institution: Pomona College
    List of Mentors: Dr. David Cliffel & Gabriel Leblanc
    Program: NSF REU 
    Research Project: Transparent Reduced Graphene Oxide Electrodes with Photosytem I for Photoconversion
    Poster: NSF REU Emily Darby Poster.pdf
    Research Abstract:
    Photosystem I (PSI) is a photoreactive electron transport protein found in plants that participates in the process of photosynthesis. Because of PSI’s abundance in nature and its efficiency with charge transfer and separation, we are interested in applying the protein to photovoltaic devices. Past research has shown increased photocurrents by integrating PSI with graphene electrodes. Here, we developed a transparent, conductive electrode using reduced graphene oxide (RGO) on which PSI could be deposited. The electrodes were characterized using Raman spectroscopy, UV-Vis spectroscopy, and electrochemical techniques; and we determined the photocurrent density in varying concentrations of several mediator solutions.

    The use of transparent RGO electrodes is an attractive alternative to graphene because it affords facile and inexpensive production through chemical processes. Furthermore, the transparency of the RGO electrode gives us the ability to utilize an opaque mediator solution, such as dichloroindophenol. The resulting photoelectrode demonstrated current densities comparable to a gold electrode modified with PSI and significantly higher than a graphene electrode modified with PSI. The relatively large photocurrents produced by integrating PSI with RGO and using an organic mediator can be applied to the production of more economic, easily produced, and completely organic solar cells.

  • Domenic DiGiovanni - Physics/Economics, Hillsdale College

    Domenic DiGiovanniEducational Institution: Hillsdale College
    List of Mentors: Dr. Yaqiong Xu & Roel Flores
    Program: NSF TN-SCORE
    Research Project: Chemical Treatment Effects on the Photoluminescence and Raman Spectra of Atomically-Thin Molybdenum Disulfide
    Poster: NSF REU Dominic DiGiovanni Poster.pdf
    Research Abstract:
    Monolayers of the transition-metal dichalcogenide molybdenum disulfide exhibit properties that could make the material ideal for future nano-scale optoelectronic applications. The monolayers’ direct bandgap property and photocurrent-generating ability makes single-layer MoS2 a promising material for use in nano-scale devices such as high-sensitivty photodetectors. This study focuses on the changes of MoS2 monolayers’ photoluminescence (PL) and Raman spectra due to chemical treatments. Samples of few-layer and single-layer MoS2 obtained using mechanical exfoliation and transferred to SiO2 substrates were treated with ozone or oxygen plasma. The flakes were identified using optical microscopy and analysis of Raman spectra; their PL and Raman spectra were measured before and at various stages during the plasma treatment. Synthesis of MoS2 monolayers using a vapor-solid method for the purpose of comparative study was also attempted and is discussed. This study demonstrates that the photoluminescence of the monolayers increases by up to a factor of four with the plasma treatments, perhaps due to the adsorption of oxygen. In the future, we plan to improve our synthesis methods and to investigate how optoelectronic properties of MoS2 phototransistors’ can be altered by chemical and x-ray treatments.

  • Jon Paul Elizondo - Mechanical Engineering, Texas A&M University

    Jon Paul ElizondoEducational Institution: Texas A&M University
    List of Mentors: Dr. Cary Pint & Dr. Rizia Bardhan &  Landon Oakes
    Program: NSF REU
    Research Project: Electrophoretic Deposition of Nanomaterials for Plasmonically Enhanced Photodetectors
    Poster: NSF REU Jon Paul Elizondo Poster.pdf
    Research Abstract:
    Nanocarbon materials coupled with plasmonically active nanoparticles show great promise in ultrafast, tunable photodetection. However, current methods for producing such devices are costly and non-scalable, making them impractical for manufacturing. In this study, we propose electrophoretic deposition (EPD) as an alternative means for fabricating structures necessary for plasmonically enhanced photodetectors. EPD is a scalable, cost-effective assembly method that utilizes coulombic interactions to deposit materials onto a substrate. Typical substrates used in the EPD process are conductors; however, through the application of novel EPD techniques we have deposited films of Au nanoparticles and graphene onto dielectrics, creating morphologies suited for plasmonic photodetection. Tests of these devices indicate slight plasmonic activity (~1% difference), and we believe that future optimization of the EPD process will significantly improve these results.

  • Timothy Haley - Physics, University of Tennessee, Chattanooga

    Timothy HaleyEducational Institution: University of Tennessee, Chattanooga
    List of Mentors: Dr. Kirill Bolotin & Hiram Conley
    Program: NSF TN-SCORE
    Research Project: Chemical Vapor Deposition of Atomically Thin Films of MoS2 for Electro-Optical Devices
    Poster: NSF REU Timothy Haley Poster.pdf
    Research Abstract:
    After graphene was developed and the scientific community began to understand its properties and limitations, it became prudent to explore other two-dimensional materials. Molybdenum Disulfide is a dry lubricant with similar properties to graphite. Likewise, we may confine it to a single layer, where it becomes an atomically thick, 2D material. Unlike graphene, monolayer Molybdenum Disulfide is a direct band gap semiconductor. This property allows monolayer MoS2 to be useful in the field of optics and will allow monolayer MoS2 to be integrated into modern electronic devices like resonators and transistors. As of now, the majority of monolayer MoS2 is obtained by using exfoliation methods. These methods produce quality monolayers but have limited flake size. Here, we explore chemical synthesis processes for creating millimeter-sized atomically thin films of MoS2. We then intend to use this material to fabricate tunable electro-optical devices. In these devices, a film of MoS2 suspended over a hole can be controllably strained using a gate electrode. Since it has been shown that the band gap of monolayer MoS2 is inversely proportional to strain, the band gap of these membranes -- and hence their optical absorption and photoluminescence -- would be tunable by controlling their deflection. These devices could have the potential to create more efficient photovoltaic devices, tunable lasers, and excitonic concentrators.

  • Jeffrey Holzgrafe - Engineering & Physics, Olin College

    Jeffrey HolzgrafeEducational Institution: Olin College
    List of Mentors: Dr. Cary Pint & Landon Oakes
    Program: NSF REU
    Research Project: Electrophoretic Deposition for Inexpensive Carbon Nano-Composite Lithium Air Battery Cathodes
    Poster: NSF REU Jeff Holzgrafe Poster.pdf
    Research Abstract:
    Lithium air batteries take advantage of a reversible oxidation reaction of lithium with O2 to create a rechargeable energy source with energy densities that could approach that of gasoline. We demonstrate that the relatively inexpensive and easily scaled process of electrophoretic deposition can be used to create carbon nanotube-nanohorn composite air electrodes for Li-air batteries. Preliminary results suggest that these composite materials improve the specific capacity of Li-air batteries over that of nanotube only materials. While significant work is still required to control and optimize these composites, the results suggest that electrophoretic deposition is a viable high-throughput process for manufacturing improved Li-air battery cathodes.

  • Olivia Hurd - Engineering, Vanderbilt University

    Olivia HurdEducational Institution: Vanderbilt University
    List of Mentors: Dr. Rizia Bardhan & Holly Zarick
    Program: NSF TN-SCORE
    Research Project: Au@SiO2 Core-Shell Nanocubes for Plasmon-Enhancement of Dye-Sensitized Solar Cells
    Poster: NSF REU Olivia Hurd Poster.pdf
    Research Abstract:
    As the need for renewable sources of energy has become a more pressing topic, a number of solutions have been presented and remain in the running as promising sources of energy, solar cells included. In order for any energy source to remain competitive, devices must constantly make advances in terms of cost and efficiency. In the field of photovoltaics, dye-sensitized solar cells (DSSCs) were introduced as an economical alternative to the traditional silicon-based solar cells, but modifications can still be made to improve the efficiencies of these DSSCs and make them more comparable to the traditional solar cells. This project focuses on improving the photo conversion efficiencies of these cells through plasmon-enhancement. Brown et al. [Plasmonic Dye-Sensitized Solar Cells Using Core-Shell Metal-Insulator Nanoparticles. Nano Lett. 2010, 11, 438-445] showed efficiency improvements through plasmon-enhancement achieved with core-shell Au@SiO2 nanospheres. Similarly, this project focuses on the integration of Au@SiO2 nanocubes. These nanocubes, as opposed to nanospheres, show near-field enhancement at their corners and edges due to localized surface plasmons, which prompts greater efficiencies in the completed cells. The DSSCs are enhanced and tested using two different incorporation geometries of the nanocubes, top layer and imbedding. Top layer geometry is achieved by airbrushing the nanocubes over the layer of titania on the anode of the cell, so that they remain mostly on top of the titania. Cells with the imbedded geometry are made by mixing the nanocubes directly into titania paste before it is added as a layer onto the cell. The efficiencies of these enhanced cells and those of reference cells lacking nanoparticles are tested using a solar simulator and a potentiostat, and the photo conversion efficiencies of DSSCs with incorporated nanocubes are found to be greater. Future work will continue to compare the efficiencies of reference cells with those of Au@Ag@SiO2 nanocube-enhanced DSSCs.

  • Jacob Jordan - Engineering, Tennessee Tech University

    Jacob JordanEducational Institution: Tennessee Tech University
    List of Mentors: Dr. David Cliffel & Gabriel LeBlanc
    Program: NSF TN-SCORE
    Research Project: Synthesis of Polyviologens as Mediators for Photosystem I-Based Assemblies
    Poster: NSF REU Jacob Jordan poster.pdf
    Research Abstract:
    Photosystem I (PSI) is a well-studied integral membrane protein that is found in algae, bacteria, and plants that mediates electron photo-excitation. When an electron within PSI is excited by light, it is transported across the protein through a series of electron accepting steps in the electron transport chain and is finally carried to the Fb site, an iron-sulfur complex that acts as a final electron acceptor. This project centers around removing electrons from the Fb site to a counter electrode in order to complete the circuit. Viologens have been an interesting mediator type to study as they have a formal potential very similar to that of the Fb site and thus can accept the electron from PSI with relatively little energy loss. Polyviologens are of specific interest as the polymer network allows increased electron transfer, reduces orientation effects, stabilizing PSI, and allowing a three-dimensional network. Electrochemical tests involving various electrode setups allowed us to generate photo-response data for polyviologens when used in conjunction with PSI. The polyviologens were synthesized using the Menshutkin reaction and characterized with 1H NMR and electrochemistry. Two different PSI-polymer electrode setups were assembled in order to test the photo-response: a gold macro-electrode system that was alternately layered with a polymer and PSI; and a heavily-P-doped silicon electrode system that used the polymers as aqueous mediators.

  • Helena Keller - Chemical Engineering, Michigan Tech University

    Helena KellerEducational Institution: Michigan Tech University
    List of Mentors: Dr. Kane Jennings & Leo Yang
    Program: NSF REU
    Research Project: Organic Monolayers on p-Doped Silicon Affect Photocurrents of Photosystem I Films 
    Poster: NSF REU Helena Keller Poster.pdf
    Research Abstract:
    Biohybrid solar cells convert light energy to electricity through the use of Photosystem I (PSI), a protein complex that drives photosynthesis in green plants. The near-one-hundred percent quantum efficiency of PSI, in addition to its vast abundance in nature, gives this technology enormous potential as a sustainable source of energy. Prior work from our group has shown that PSI films on p-doped silicon yield photocurrents that approach 1 mA/cm2, far exceeding those for PSI on metals or for unmodified silicon. In this project, we have investigated the use of organic monolayers deposited between the p-doped silicon semiconductor and the PSI layer to facilitate electron transfer and increase the stability of the PSI film. These monolayers were prepared by exposing silicon to solutions containing -terminated alkynes to produce an alkenyl attachment of the monolayer to silicon and create a surface of the -terminated functionality for interaction with PSI. Of the monolayer surface groups tested, including alcohols, amines, carboxylic acids, and covalently reactive groups, the carboxylic acid terminus most consistently achieved the highest photocurrents, suggesting favorable electrostatic attraction between the negative surface of the monolayer and positive patches on PSI. Carboxylic acids of varying carbon chain lengths—specifically three, five, six, and seven carbons—were then tested using photochronoamperometry in order to observe the effect of monolayer thickness on photocurrent as well as the stability of the photocurrent over time.

    • Helena presented her summer research poster at the 2013 AIChE Annual Meeting: Global Challenges for Engineering a Sustainable Future, San Francisco, CA.
  • John Lonai - Physics & Engineering, Northwest Nazarene University

    John LonaiEducational Institution: Northwest Nazarene University
    List of Mentors: Dr. Sharon Weiss & Gilbert Rodriquez
    Program: NSF REU
    Research Project: Optimized porous silicon Bloch surface and sub-surface wave structure for simultaneous detection of small and large molecules
    Poster: NSF REU Poster John Lonai.pdf
    Research Abstract:
    A Porous silicon (PSi) Bloch surface and sub-surface wave (BSW/BSSW) biosensor is optimized and demonstrated for the size selective detection of both small and large molecules. PSi biosensors have been previously shown to offer enhanced label-free sensing of small biological and chemical molecules that can infiltrate the pores due to a large internal surface area and tunable optical properties. The PSi BSW/BSSW biosensor offers the possibility to sensitively detect both small molecules that infiltrate the pores and large molecules attached on the sensor surface. The BSW/BSSW structure consists of a periodic stack of high and low refractive index layers, known as a Bragg mirror, with a reduced optical thickness surface layer. The truncated surface layer gives rise to a BSW with an evanescent tail that extends above the surface and enables the detection of large surface-attached molecules that cannot penetrate the porous matrix. Implementation of a step or gradient refractive index profile within the Bragg mirror generates a large electric field intensity spatially localized to a desired region of the mirror, known as the BSSW. The BSSW mode is entirely confined within the multilayer Bragg mirror and can detect small molecules attached within the pores with an enhanced sensitivity compared to other PSi biosensor designs. The design and experimental realization of optimized step and gradient refractive index profiles necessary to realize the BSSW is presented here for the first time. The PSi BSW/BSSW biosensor is designed using rigorous coupled wave analysis and transfer matrix theory simulations. Size-selective molecular detection is demonstrated using a prototypical small chemical molecule, 3-Aminopropyltrimethoxysilane (3-APTES; size of 0.8 nm) and large, 60 nm carboxyl latex nanospheres. Attachment and quantification of the small and large species are performed by monitoring the angle-resolved reflectance spectrum of the PSi BSW/BSSW structure. The BSW and BSSW modes are each manifested as a distinct resonance peak in the spectrum, and the angular shift of each peak can be used to quantify the number of molecules or nanospheres attached to the sensor. Detection and quantification of the 3-APTES attachment and nanosphere binding is separately performed with the BSSW mode and BSW mode, respectively. Good agreement between theoretical simulations and experimental measurements is found for both the PSi step and gradient BSW/BSSW biosensors. The size-selective detection of both small and large molecules using the same sensor platform is expected to be a significant advantage for future multi-analyte detection schemes using a microfluidics approach.

  • Katina Mattingly - Engineering & Physics, Murray State University

    Katina MattinglyEducational Institution: Murray State University
    List of Mentors: Dr. Jason Valentine & Wei Li
    Program: NSF REU
    Research Project: Development of nanophosphor films for use in thermometry of nanoscale thermoplasmonic antennae
    Poster: NSF REU Katina Mattingly Poster.pdf
    Research Abstract:
    With a variety of applications in optics, semiconductors, and drug delivery; thermoplasmonic nanoantennae, which act as nanoscale heat sources, have a growing need for optimization and characterization. Current thermometry techniques that implement phosphors involve a high temperature annealing step. This step, used after deposition of the phosphor film, limits the device design and allowable substrates. In this project, an improved thermometry technique based on nanophosphors is investigated in an effort to improve current thermal characterization ability. To achieve maximum detector coverage, a nanoparticle phosphor film has been developed. Cerium doped yttrium aluminum garnet phosphor powder was first created via combustion synthesis and then transformed into nanoparticles via laser ablation. The nanoparticles are distributed onto nanoscale plasmonic devices in a uniform film that is utilized to detect the local temperature through the temperature dependent photoluminescence lifetime of the phosphor. The proposed thermometry technique removes the necessity of an annealing process, allowing for greater flexibility in device design and material. This research will help optimize thermometry of thermoplasmonic antennae and remove limitations on design parameters.

  • Marc Panu - Chemical Engineering, Vanderbilt University

    Marc PanuEducational Institution: Vanderbilt University
    List of Mentors: Dr. Bridget Rogers & Courtney Mitchell
    Program: NSF TN-SCORE
    Research Project: Fabrication of Gadolinium Aluminum Garnet Phosphor by Combustion Synthesis
    Poster: NSF REU Marc Panu Poster.pdf
    Research Abstract:
    Cerium-doped gadolinium aluminum garnet (GAG:Ce) can be used to improve the efficiency of white-light LEDs (light emitting diodes). The Rogers group has gained expertise in combustion synthesis of yttrium aluminum garnet doped with Ce and/or Eu, however the process procedure does not produce good quality, pure phase GAG. This project focused on developing a gel-combustion synthesis of GAG:Ce. Photoluminescence (PL) spectroscopy, powder x-ray diffraction (XRD), and x-ray photoelectron spectroscopy (XPS) were used to characterize the effects of processing conditions on the resulting materials’ properties. Fuel type, combustion temperature, annealing temperature and annealing time were investigated. XRD showed that nearly pure phase GAG was formed by using citric acid as the fuel, a combustion temperature of 500°C, and a 4.5 hour, 1100 °C anneal. The trends observed in our results are consistent  with phase diagrams that indicate pure-phase GAG should be formed at 1200 °C and above. Material combusted at 400 °C and annealed for 14 hours at 1100 °C had the most intense PL emission but did not contain the most garnet phase of the materials produced. This observation indicates PL emission intensity depends on factors in addition to crystal phase. We investigated the effects of host doping on GAG PL intensity. Yttrium was substituted for gadolinium, and gallium was substituted for aluminum in the GAG lattice. XRD and XPS analyses were used to interpret the trends in PL emission of these host-doped materials.

    • Mark presented his summer research poster at the GEM 2013: Expanding Our Horizons in San Juan, Puerto Rico, the 2013 AICHE conference in San Francisco, CA, the 2013 National Society of Black Engineers -Region 3 in Lexington, KY, where he won first place and was invited to present his poster at the National NSBE conference which was held in Nashville.
  • Michael Reynolds - Physics, Columbia State Community College

    Michael ReynoldsEducational Institution: Columbia State Community College
    List of Mentors: Dr. Richard Haglund & Jed Ziegler
    Program: NSF REU
    Research Project: Good Vibrations: Plasmon-Exciton Coupling in Gold/Molybdenum Disulphide Hybrid Systems
    Poster: NSF REU Michael Reynolds Poster.pdf
    Research Abstract:
    Monolayer Molybdenum Disulphide (MoS2), a two dimensional transition metal dichalcogenide, has interesting optical and electronic characteristics, specifically a direct optical band gap of 1.85 eV that is tunable by stress, applied voltage, as well as optical excitation source intensity. This band gap along with a large (0.5 eV) exciton binding energy makes MoS2 an attractive candidate for applications in two dimensional photoelectronics. In this study, we intend to couple the excitons from MoS2 to a second species of bound state generated in gold nanoparticles, the local surface plasmon, which is the oscillation created by electron cloud and photon wave coupling as light passes through metallic particles. We fabricate gold nanorods of varying lengths on top of MoS2 flakes separated by a spacer layer to promote direct coupling between the two bound states, excitons and plasmons. Photoluminescence measurements are taken using excitation energies at 532 nm and 633 nm, to probe the exciton-plasmon binding behavior of the hybrid system. This system presents in two configurations, which are observable in the photoluminesce and extinction spectra: off resonant enhancement or on resonant binding. Off resonant enhancement occurs when the resonant energy of the plasmon occurs at a higher energy than the energy of the exciton, resulting in an increase in exciton emission intensity. On resonant binding occurs when the resonant energy of the plasmon is equal to the exciton energy and results in a significant blue shift and enhancement of the MoS2 excitonic photoluminescent peaks. This typically signifies strong, coherent coupling between the exciton and plasmon, a bound state termed plexcitons. The plexciton could be used to modulate and enhance the excitonic properties of MoS2 and thereby introduce further versatility to MoS2-based two dimensional transistors.

  • Ryan Rhoades - Physics & Applied Math, Florida State University

    Ryan RhoadesEducational Institution: Florida State University
    List of Mentors: Dr. Richard Haglund & Rod Davidson
    Program: NSF REU
    Research Project: Mapping Plasmonic Response of Nanostructures via Multiphoton Absorption in Poly (methyl methacrylate)
    Poster: NSF REU Ryan Rhoades Poster .pdf
    Research Abstract:
    The near-field plasmon response of nanoparticles has previously been mapped by complex techniques such as electron energy-loss spectroscopy (EELS) and scanning near-field optical microscopy (SNOM). However, recent research has shown that four-photon absorption in poly(methyl methacrylate) (PMMA) is a more efficient way to map and characterize localized surface-plasmon resonance modes. In this work, the use of PMMA development as an optical means to characterize plasmonic responses in the near-field is verified with simple nanoparticles and then applied to more complex structures with resonance modes that have been only computationally observed. Nanoparticles were spin-coated with PMMA, exposed to an Ti:sapphire laser to induce areas of intense electric fields that cause polymer scission. Once the polymer is developed, it is characterized by scanning-electron microscopy to create an electric near-field intensity profile that corresponds with areas where the strong localized surface-plasmon resonance has generated the largest electric field. This process then will be used to experimentally map multiple plasmonic modes in gold Archimedean nanospirals. Future studies will refine and optimize this characterization technique and apply it to additional complex resonance modes in nanospirals and other asymmetric nanoparticles.

  • John Shannon - Biochemistry, Colorado State University

    John ShannonEducational Institution: Colorado State University
    List of Mentors: Dr. James Crowe
    Program: NSF REU
    Research Project: Exploring Respiratory Syncytial Virus Fusion and Matrix Protein Interactions in Membranes Using Recombinant Proteins and Nanodiscs
    Poster: NSF REU John Shannon Poster .pdf
    Research Abstract:
    Respiratory syncytial virus (RSV) belongs to the Paramyxoviridae family and is the leading cause of severe viral respiratory disease in young children, the elderly and immunocompromised individuals. Currently, there is no effective vaccine available and each year there are over 64 million reported cases of RSV resulting in ~160,000 deaths worldwide. RSV infects predominately epithelial cells of the upper respiratory tract, and little is known about how the virus mediates viral assembly and release in the host. In cell culture systems, it has been shown that RSV infects at, and is released from, the apical surface of polarized cells and exhibits distinct and dynamic filamentous structures in non-polarized cells. Our laboratory has previously shown that RSV viral filament formation requires interaction of the viral nucleoprotein (N), matrix (M) protein, and phosphoprotein (P) through a terminal phenylalanine (Phe) residue of the fusion protein cytoplasmic tail (F CT). We hypothesized that RSV M and RSV F have a transient interaction that mediates assembly of the viral proteins into filamentous structures prior to budding and release from epithelial cells. Data provided here using site-directed mutagenesis and confocal microscopy show attenuated filament formation in RSV M mutants, as compared to those that possess the wild-type sequence of M protein. Given the transient nature between RSV M and F, it has been difficult to detect the interaction through commonly used molecular and cell biology techniques. We sought to develop an innovative method to examine the transient interaction between these viral proteins utilizing nanodiscs and Förster resonance energy transfer (FRET). We generated a RSV F CT wild-type recombinant soluble protein and a F CT (F22A) mutant protein to be assembled and displayed in a nanodisc platform, and we used these constructs in interaction assays using FRET-based technologies. This approach will provide a practical method for examining transient protein-protein interactions that occur only in the context of lipid bilayer membranes. Data obtained through these various assays provides insight into the mechanism controlling RSV viral egress, leading towards the development of novel disease interventions

    • John Shannon presented his summer research at the 2014 Keystone Symposia: Pathogenesis of Respiratory Viruses, Keystone Colorado.
  • Corban Swain - Biomedical Engineering, Washington University, St. Louis

    Corban SwainEducational Institution: Washington University, St. Louis
    List of Mentors: Dr. Craig Duvall & Chris Nelson
    Program: NSF REU
    Research Project: Controlled Release of siRNA from Hydrolytically Degradable Nanomicelles for Potent Gene Knockdown
    Poster: NSF REU Corban Swain Poster .pdf
    Research Abstract:
    RNA interference—an endogenous system in eukaryotic cells by which double-stranded RNAs lead to the degradation of complementary mRNA—can be exploited by small interfering RNAs (siRNAs) to silence almost any gene in the human body.[1] This premise allows siRNA to be utilized as a targeted therapeutic agent against disease. However, siRNA alone is prone to degradation by enzymes and marked by limited transfection into cells; moreover, delivery is the primary barrier to the use of siRNA as a therapeutic. Our previous work has shown safe and effective delivery of siRNA and gene silencing in cells with the use of PEG-shielded#, pH-responsive, endosomolytic, micellar nano-polyplexes (NPs) formed from diblock copolymers[2] (poly(EG-b-[BMA-co-DMAEMA]))*.

    Intracellular release of siRNA from NPs once they have been internalized is a limiting step in siRNA bioavailability and bioactivity. In this study, working under the motivation to have greater siRNA release post endosomal escape, we employ a new set of polymers (poly(EG-b-[BMA-co-DMAEA]))** capable of self-catalyzed hydrolysis. In aqueous solution, poly(DMAEA) will degrade to poly(acrylic acid) and a benign alcohol; by this process the positive charge on the BMA-co-DMAEA polymer block will undergo charge reversal over time, leading to decomplexation and release of negatively charged siRNA. Förster resonance energy transfer (FRET) studies showed our hydrolytically degradable (HDG) NPs to have significantly greater release (with tunability) of labeled DNA over time when compared to non-HDG NPs. Flow cytometry measurements showed comparable cellular uptake for HDG NPs vs. non-HDG NPs at multiple dosages, proving that cellular uptake is not significantly reduced despite the different polymer chemistry of our HDG NPs. These data suggest that HDG NPs are a novel platform to improve siRNA gene silencing through enhanced intracellular bioavailability. Ongoing work will confirm improved intracellular release and bioactivity of HDG NPs relative to our established non-HDG NP system.

    • Corban gave an oral presentation of his summer research poster at the 2013 Annual Meeting of the Biomedical Engineering Society, Seattle, WA.
  • Miranda Trentle - Chemistry, University of Tennessee, Chattanooga

    Miranda TrentleEducational Institution: University of Tennessee, Chattanooga
    List of Mentors: Dr. Rizia Bardhan & Will Erwin
    Program: NSF TN-SCORE
    Research Project: Large Area Nanoplasmonic Architectures for Solar Applications”
    Poster: NSF REU Miranda Trentle Poster .pdf
    Research Abstract:
    Solar energy represents a transformational energy resource for future sustainability. Everyday ~0.56x1022 J of energy is incident on Earth from sunlight. By efficiently harvesting only 7 % of this incident light in one day, the global energy needs (0.41x1021 J) for one year can be effectively fulfilled. Solar energy driven dye-based and polymer-based organic solar cells offer a promising and inexpensive alternative to crystalline Si solar cells; however, the efficiencies of these organic solar cells remain <10%. Recent advances have demonstrated that plasmon resonances in metal nanostructures can be engineered to enhance carrier collection in adjacent molecules and semiconductors resulting in significant optical enhancements and better performance. However, the integration of plasmonic nanostructures for enhanced photon concentration in organic solar cells remains in its infancy due to the lack of conceptual understanding of plasmonic engineering. Therefore in this project I have designed large area plasmonic architectures with various geometries and dimensions, and unique optical resonances enabling the capture of broadband solar radiation. These wafer scale nanoplasmonic architectures have ideal surface characteristics to directly integrate with organic and inorganic media for solar device fabrication.

    The plasmonic architectures (nanoholes, Fischer patterns, and nanocups) were designed by nanosphere lithography (NL). In NL a close-pack monolayer of polystyrene or silica nanospheres are formed on a substrate by self-assembly, followed by metal deposition to generate an array of plasmonic architectures. Unlike electron beam lithography which is reproducible but is a slow, expensive process, NL has low precision, but is relatively fast and cost effective. In our approach we casted a closed-packed layer of nanospheres on the surface of water and then transferred the free-floating nanosphere mask on a solid substrate. Long range ordering (~ 1 cm x 1 cm) with very few defects were observed using this method of NL. By using nanospheres of different sizes, and combing Cr/Au deposition by electron beam and reactive ion etching, we generated plasmonic Fischer patterns and nanoholes of variable diameters and pitch length. The plasmon resonances of these large area architectures are highly tunable by simply altering the nanosphere size. Our experimental absorption properties demonstrate a broadband absorption across the visible and near-field overlapping with the solar spectrum. We are currently designing routes to integrate these with standard dye-sensitized solar cells to achieve higher efficiency by plasmonic enhancement.

2012

  • Keisha Carr - Chemical Engineering, University of Maryland

    Keisha CarrEducational Institution: University of Maryland, Baltimore County
    List of Mentors: Dr. David Piston and Dr. Tara Schwetz
    Program: NSF REU
    Research Project: α-cell Response to Low Glucose
    Poster: NSF REU Keisha Carr Poster.pdf
    Research Abstract:
    Pancreatic α-cells play an important role in regulating glucose homeostasis by secreting glucagon during hypoglycemia. To date, it has been poorly understood how intact α-cells respond to very low levels of glucose (less than 1mM). To elucidate α-cell behavior within the islet, mouse islets were loaded with Fluo4-AM, a calcium (Ca2+) indicator dye, to detect changes in intracellular Ca2+. The islets were exposed to glucose concentrations between 0.1 and 5 mM and the changes in α-cell parameters were determined by confocal microscopy. Further, two-photon excitation microscopy was used to measure the combined autofluorescence of NADH and NADPH (NAD(P)H, collectively), which serves as a cellular redox state indicator and provides information on the cell's metabolic activity. NAD(P)H autofluorescence was measured as a function of glucose (between 0.1 and 5 mM). As glucose concentration increases, both Ca2+and NAD(P)H activity also increase. However, there is minimal activity at 0.1 mM glucose in the α-cells. These data show that intact α-cells exhibit a reponse to glucose even at very low concentrations. Thus, it is postulated that α-cell activity as a function of glucose may be left-ward shifted compared to the β-cell, which is active at higher glucose levels.

  • William Crosby - Chemistry, University of Tennessee - Martin

    William CrosbyEducational Institution: University of Tennessee, Martin
    List of Mentors: Dr. David Cliffel and Gabriel LeBlanc
    Program: NSF TN-SCORE
    Research Project: Photoreduction of Graphene Oxide with Photosystem I
    Poster: NSF REU Will Crosby Poster.pdf
    Research Abstract:
    Photosystem I (PSI) is a protein in green plants that carries out the processes of photosynthesis. Graphene has shown potential and popularity in electronics research due to its high conductivity and optical transparency. Graphene can be produced through the oxidation of graphite, producing graphene oxide (GO) followed by thermochemical reduction to reduced graphene oxide (rGO). Here we aimed to combine PSI and rGO in order to produce an efficient, photoactive electrode with many applications. We prepared the biohybrid composite by photoreducing GO to rGO using PSI as a photoactive reducing agent. This alternative reduction method lowers the risk of denaturing PSI, which is likely with the high heat and harsh chemicals used in traditional reduction methods of GO. The resulting biohybrid composite demonstrated decreased solubility in water after exposure to light, which we attributed to the partial reduction of the GO. This insolubility greatly benefits the composite deposition on electrodes for use in aqueous experiments as it promotes good contact with the electrode surface and thus faster electron transfer. The new PSI-rGO composite material was characterized using UV-Vis spectrophotometry, Raman spectroscopy, and various electrochemical techniques. It has been shown that PSI-rGO biohybrid composites can be prepared and deposited on many electrode materials while still maintaining photoactivity.

  • Karla Dumeng - Chemical Engineering, University of Puerto Rico at Mayaguez

    Karla DumengEducational Institution: University of Puerto Rico at Mayaguez
    List of Mentors: Dr. Kane Jennings and Darlene Gunther
    Program: NSF REU
    Research Project: The Improvement of Photosystem I Deposition Using a Spin-coating Method
    Poster: NSF REU Karla Dumeng Poster.pdf
    Research Abstract:
    Photosystem I (PSI) is a photocatalytic protein complex that drives photosynthesis in green plants and cyanobacteria. PSI extracted from plants and deposited onto a surface can covert solar energy to electrical energy. Previous methods, such as vacuum-assisted assembly, face challenges when depositing PSI onto an active electrode, including lengthy deposition time and controlling the coverage and uniformity of the PSI film. Here we deposit PSI, which is extracted from the spinach leaf, onto a gold substrate by spin-coating for the first time in order to optimize the coverage of the PSI layer. The spin-coating method consists of adding an aqueous solution of PSI onto a gold substrate and then rotating it to remove the water from the system, obtaining a thick film of PSI that can be rinsed down to a dense monolayer. Electrochemical experiments using a 3-electrode cell show that photocurrents of ~50-100 nA/cm2 are obtained for samples with thicknesses of ~40-80 Å. The spin-coating method provides improved uniform deposition of PSI, is an order of magnitude faster than vacuum-assisted assembly, and creates a consistent light-induced current. For future work, we will deposit thicker films of PSI with the aim of increasing the photocatalytic response of the system.

    • Karla Dumeng presented her poster at the 2012 Ana G. Mendez University System Research Symposium, San Juan, PR and the 2012 American Institute of Chemical Engineers Annual Meeting, Pittsburgh, PA.
  • Adam Edwards - Chemical Engineering, Tennessee Technological University

    Adam EdwardsEducational Institution: Tennessee Technological University
    List of Mentors: Dr. Peter Pintauro and Matt Brodt
    Program: NSF TN-SCORE
    Research Project: Nanofiber Composite Membranes for Formic Acid Fuel Cells
    Poster: NSF REU Adam Edwards Poster.pdf
    Research Abstract:
    Direct formic acid fuel cells (DFAFCs) have great potential for portable power applications. DFAFCs have the advantages of high efficiency and reasonable power densities (156 mW/cm2) at low temperatures. While DFAFCs have been proven to be less susceptible to fuel crossover than direct methanol fuel cells, crossover still occurs and is a function of concentration and temperature. Unreacted fuel that permeates from the anode to the cathode can create a mixed potential, flood the cathode, and decrease the efficiency of oxygen reduction. This research project is focused on making low formic acid crossover membranes. A dual-nanofiber electrospinning approach was employed where composite membranes composed of Nafion and poly (phenyl sulfone) were prepared. The performance of the composite membranes in direct formic acid fuel cells was measured and compared with commercial Nafion 212 film at 40oC. The resistance to water swelling of composite membranes should reduce the permeability of fuel crossover in formic acid fuel cells, thus providing an alternative polymer electrolyte membrane for future DFAFC applications.

  • Robert Fuller - Physics, Villanova University

    Robert FullerEducational Institution: Villanova University
    List of Mentors: Dr. Sharon Weiss, Jeremy Mares, Gilbert Rodriguez
    Program: NSF REU
    Research Project: Real-Time Biomolecular Sensing with Porous Silicon Microcavity Films
    Poster: NSF REU Robert Fuller Poster.pdf
    Research Abstract:
    Porous silicon has become a very promising material for biological sensing due to its large internal surface area, tunable optical properties, and rapid fabrication. Present transducers have limited porous silicon devices to the confines of a lab; however, with the integration of a microfluidic channel, real-time sensing is achievable with applications in medical, food, environmental, and military monitoring. In this work, we report on the demonstration of real-time sensing in porous silicon microcavities integrated with microfluidic channels and the evaluation of molecular diffusion speeds and size-dependent molecular sensing in the pores. Electrochemical etching is used to create the porous films on silicon wafers. The etching parameters are adjusted to produce films with multiple layers of various thicknesses and porosities, allowing the optical properties of the film to be carefully tuned. The porous silicon microcavity structure used in this study consists of a pair of multilayer Bragg mirrors separated by a cavity or “sensing” layer deep within the structure. The reflectance spectrum of the microcavity is characterized by a sharp resonant dip. Introduction of an analyte into the film changes the effective refractive indices of the porous layers, causing a shift in the cavity’s resonant wavelength. The magnitude of the shift quantifies the amount of analyte in the cavity. Porous silicon microcavities were exposed to two different lengths of DNA molecules. Unlike prior work that suggest long diffusion times for molecules to reach the active sensing region of the microcavities, real-time sensing experiments performed in this study show that small molecule infiltration times are comparable to thinner porous sensing structures. However, due to the buried active sensing region, size-dependent sensitivity of molecular detection was observed. Detection of short, 8-mer DNA at concentrations as low as 18uM was demonstrated, while 40-mer DNA was found to not have a resolvable spectral shift, likely due to the inability of the larger molecule to penetrate deep inside the porous film to the active sensing region of the microcavity. In summary, porous silicon microcavity sensors integrated with microfluidic channels are promising for the real-time detection of small molecules and have the ability to size-selectively filter out larger molecules.

  • Walter Harrington - Biochemistry, University of Tennessee, Chattanooga

    Walter HarringtonEducational Institution: University of Tennessee, Chattanooga
    List of Mentors: Dr. Jim Davidson and Hank Paxton
    Program: NSF TN-SCORE
    Research Project: Diamonds are a Sun’s Best Friend: A study to improve TEC efficiency using solar energy
    Poster: NSF REU Walter Harrington Poster.pdf
    Research Abstract:
    Thermionic Energy Conversion (TEC) is a means by which thermal energy can be directly converted into electrical energy, bypassing the conventional need to go through the medium of mechanical energy via a generator. When a material is heated, electrons with sufficient energy will be emitted through a process known as thermionic emission. A current can be established using this principle by engineering a “hot emitter” nanometers away from a “cooler emitter,” thus capitalizing on the flow of electrons from hot to cold surfaces. Diamond is one of the most efficient electron emitting materials known; this study examined the photoconductivity of a boron doped diamond film deposited on a molybdenum substrate as a means to create a more efficient TEC device capable of using solar energy as both the thermal and photonic source. The results obtained imply that a thermionic device using diamond as the electron emitter could be enhanced though solar photons. Thermal tests were similarly run on the diamond film to characterize its behavior in relation to temperature. A conceptual study was also performed which shows the use of preexisting solar concentrators would be sufficient to reach the temperature needed for a diamond TEC device to operate. By using solar energy to heat the diamond, the TEC device could benefit from the diamond’s inherent photoconductivity along with its high rate of thermionic emission from heating alone.

  • Albert Hinman - Biological Sciences, Virginia Polytechnic Institute and State University

    Albert HinmanEducational Institution: Virginia Polytechnic Institute and State University
    List of Mentors: Dr. Scott Guelcher and Jon Page
    Program: NSF REU
    Research Project: The Synthesis, Optimization, and Characterization of Polyurethane Foams
    Poster: NSF REU Albert Hinman Poster.pdf
    Research Abstract:
    NSF There is a need for regenerative therapies for soft tissue applications that have lower costs, less invasive procedures, and can deliver biologics more effectively. Injectable polyurethane foams have been shown to be applicable for these purposes, primarily for soft tissue repair applications. For this study, novel diisocyanates were utilized to develop injectable polyurethane foams for soft tissue repair. Two unique, fully degradable diisocyanates, para-amino benzoic acid-lactide-diethylene glycol (PLD) and para-amino benzoic acid-glycolide-diethylene glycol (PGD),were compared along with two common urethane blowing catalysts, triethylene diamine (TEDA) and dimethyl aminoethyoxyethanol (DMAEE) for maximal foam efficiency. The foams were composed of a degradable isocyanate, water, sucrose bead fillers, and a degradable, trifunctional polyester (polyol). Each formulation was analyzed for utilization as an injectable graft. The diisocyanates used in the study allowed for microphase separation through unique hard segment symmetry. The hydrogen bonded microdomains allow for greater mechanical properties when dry. However, the foams weaken in aqueous environments due to water breaking the hydrogen bonding. Glass transition temperatures were determined with dynamic scanning calorimetry. PLD foams had a Tg -4oC, while PGD foams had a Tg 24oC.. Formulations were tested for porosity both gravimetrically and via electron microscopy with each catalyst and isocyanate. A peak porosity value around 86% was attained for each formulation. Additional porosity was created by the addition of the sucrose filler. The sucrose can be quickly leached out for an additional 5-7% porosity. This increases interconnectivity and can allow for better cellular infiltration in vivo. Cytotoxicity analysis showed that DMAEE is lethal to cells while TEDA is nontoxic. TEDA was utilized for the remainder of the experiments. PLD and PGD foams had an elastic modulus ranging from 50-90 kPa. Degradation testing has shown that the foams remain stable in vitro up to 21 days. Further work in this study can demonstrate the effectiveness of the polyurethane diisocyanate networks effects within synthetic regenerative medicine.

  • Erik Jewell - Chemistry, Austin Peay State University

    Erik JewellEducational Institution: Austin Peay State University
    List of Mentors: Dr. Janet Macdonald and Emil Hernandez
    Program: NSF TN-SCORE
    Research Project: Photodegradation study of Copper (I) Oxide nanoparticles synthesized with different geometries
    Poster: NSF REU Erik Jewell Poster.pdf
    Research Abstract:
    Copper (I) Oxide (Cu2O) has been widely researched as a photocathode for overall water splitting due to its high absorption in the visible range, with a band gap of 2.2 eV. In addition, it is made of abundant, inexpensive, and non-toxic elements, making it suitable for large scale production. However, this material photodegrades under conditions required for practical photoelectrochemical cells (PECs), which hinders its application. In order to develop preventative techniques, fundamental studies of the degradation process are desired. A major question is how does this degradation vary for Cu2O with different exposed crystal facets. To this end we have synthesized cubic, truncated octahedral, and bipyrimidal Cu2O nanoparticles. Structural characterization was carried out by Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), and Transmission Electron Microscopy (TEM). The particles were then used as photocathodes in a PEC, and their photodegradation was studied employing cyclic voltammetry under dark and illuminated conditions.

    • Eric Jewell presented his summer research at the 2013 American Chemical Society Meeting in New Orleans, LA.
  • James Kintzing - Chemistry, Grove City College

    James KintzingEducational Institution: Grove City College
    List of Mentors: Dr. Craig Duvall and Chris Nelson
    Program: NSF REU
    Research Project: PEG-Cloaked, pH-Responsive Nanomicelles for Effective and
    Poster: NSF REU James Kintzing Poster.pdf
    Research Abstract:
    Small interfering RNA (siRNA) is a potent mediator of cellular expression and can be used to assert precise control over cell behavior. Harnessing the power of gene therapy through siRNA is emerging as powerful approach to disease treatment. This auspicious technique hinges on the development of a safe and effective delivery mechanism. A variety of polymer formulations have been proposed as a method for carrying genetic material into cells, but many existing schemes have been hindered by barriers to successful delivery. An efficacious carrier must overcome the hurdles of enzymatic degradation, cytotoxicity, and endosomal escape to make treatment feasible. In this study, a novel pH-responsive diblock polymer (polyethylene glycol–[block]–2–(dimethylamino)ethyl methacrylate–[co]–butyl methacrylate) is used to form nanomicelles that encapsulate siRNA, forming nanomicelle polyplexes (NMPs). The micelle corona is composed of a polyethylene glycol (PEG) shell, which cloaks the surface charge and improves biocompatibility. NMPs are characterized using dynamic light scattering and transmission electron microscopy and have a hydrated diameter of ~100nm. NMPs have a measured zeta potential of 0mV, which confirms the ability of PEG to cloak the internal charge. NMPs are both stable and nontoxic over time and remain inert and intact when incubated in human whole blood. Cell uptake, measure by flow cytometry, shows slow internalization compared to commercial standards, yet gene knockdown assays demonstrate that slight uptake of NMPs is enough to maintain acute gene silencing activity. Treated cells experience up to 75% reduction in gene expression after 48 hours. These results indicate that NMPs escape endosomal trafficking and deliver siRNA with exceptional release efficiency. The development of an innocuous siRNA carrier with maintained delivery capacity and whole blood stability provides strong support for the plausibility of intravenous micelle injection. The findings of this study suggest that NMPs are a useful platform for siRNA delivery and can be effective in-vivo via IV injection.

  • Laura Lanier - Polymer & Fiber Engineering, Georgia Institute of Technology

    Laura LanierEducational Institution: Georgia Institute of Technology
    List of Mentors: Dr. Eva Harth
    Program: NSF REU
    Research Project: Controlled Branching of Glycidol Polymers and Subsequent Formation of Bioconjugates with Improved Biocompatibility
    Poster: NSF REU Laura Lanier poster.pdf
    Research Abstract:
    Glycidol, an analog of ethylene glycol, provides a promising polymer system for medical applications of nanomaterials. Due to their hydroxyl functionality, glycidol polymers are inherently hydrophilic, an important property for applications inside the body, such as nanoparticles for drug delivery and solubilization for biomolecular transport. Polymerization of glycidol proceeds through a ring-opening polymerization of the epoxide ring, and as the epoxide ring can open in two ways, these systems are generally hyperbranched. Linear systems are possible, but the process is more complicated and oxygen sensitive. However, it has been recently determined that the amount of branching in the system can be kinetically controlled. Being able to control the amount of branching easily is very desirable, as it allows polyglycidol to be tuned for specific applications, including biomaterials, nanoparticles, and biomolecular transport. Part of this study focused on incorporation of a second monomer with allyl functionality into the system. The desired monomer has epoxide functionality for ring-opening polymerization, allyl functionality for post-modification, and an ester group to impart degradability on the system. However, incorporation of this mixed length glycidyl ester allyl (MLGEA) monomer into the glydicol polymer is difficult as the polymerization of the MLGEA proceeds much more slowly than that of the glycidol. This problem was addressed through the use of an analog of glycidol with a protected hydroxyl group. The second part of this study focused on grafting polyglycidol to proteins to increase solubilization and biostability of the biomolecule. Maleimide alcohol was attached to the free thiols of bovine serum albumin (BSA), and glycidol polymers were grown directly from these alcohols on the protein. The bioactivity of these conjugates will be studied using a bioactivity assay. Future work will study the effect of branching on the bioactivity of the protein.

  • Marc-Andre LeBlanc - Chemistry & Physics, Lyon College

    Marc-Andre LeBlancEducational Institution: Lyon College
    List of Mentors: Dr. Eva Harth
    Program: NSF REU
    Research Project: Synthesis and Characterization of Polyester Nanosponges for Drug Delivery
    Poster: NSF REU Marc-Andre LeBlanc Poster.pdf
    Research Abstract:
    Poor water solubility is one of the most significant and fundamental barriers limiting drug delivery. Not surprisingly, many promising chemotherapeutics, antibiotics, and peptide therapeutics have failed clinically due to solubility issues. A recent approach with the potential to fix the issue of solubility uses nanoparticles to encapsulate the potential therapeutic. By using biodegradable nanoparticles, or nanosponges, it is possible to increase the solubility of the therapeutic without altering the drug itself. These nanoparticles are formed by covalently cross-linking linear, functionalized polyesters. The functional groups included in the polyesters allow us to add targeting ligands or imaging agents after nanoparticle formation, enabling targeted drug delivery and imaging. Our current research focuses on optimizing the synthesis of both the polyesters and the nanoparticles. In the synthesis of the polyesters, by increasing the amount of catalyst and using precipitation in place of dialysis we have reduced the previous three day synthesis to six hours. Additionally we have started optimizing the cross linking process, running a kinetics study to ensure optimal reaction time. After completing optimization, we will move on to test the drug encapsulation ability of the particles using thiostrepton, a powerful breast cancer drug that is completely water-insoluble. Finally we will utilize imaging dyes to monitor biodistribution of our tumor-targeted nanoparticles in vivo.

  • Ruben Medina-Perez - Physics, California State University

    Ruben Medina-PerezEducational Institution: California State University, Dominguez Hills
    List of Mentors: Dr. Kalman Varga and Dr. Sergiy Bubin
    Program: NSF REU
    Research Project: Investigation of electron and ion dynamics in small hydrocarbons subjected to short intense laser pulses
    Poster: NSF REU Poster Ruben Medina.pdf
    Research Abstract:
    With advances in lasers, the last two decades have seen a growing interest in studying the interaction of matter with strong electric fields. In particular, there have been recent experiments with small hydrocarbon molecules subjected to short intense laser pulses. While a lot of interesting features can be determined through the experimental measurements of fragments formed in the process of the light-matter interaction, the internal electron and ion dynamics often remains vague. In this work, we study the ion dynamics in methane and ethylene subjected to 17 fs (FWHM) pulses of intensities of 8, 16, and 24 * 1014 W/cm2. These molecules represent a simple, yet nformative, case when the details of the dynamics taking place during the Coulomb explosion can be studied. In the framework of time-dependent density functional theory (TDDFT) complemented with the Ehrenfest molecular dynamics, we have performed numerical simulations which provide an insight into the mechanism of Coulomb explosion in small molecules. In particular, we have shown that the ejection of protons occur simultaneously, thereby confirming the all-at-once scenario proposed by Roither et al. [Phys. Rev. Lett. 106, 163001 (2011)]. We have found that for higher intensity pulses the kinetic energies of the protons ejected in each explosion are very similar in magnitude. We have also studied the orientational dependence of the fragmentation process by repeating the calculations for several representative configurations.

  • Barclay Randall - Physics, Middle Tennessee State University

    Barclay RandallEducational Institution: Middle Tennessee State University
    List of Mentors: Dr. Sandra Rosenthal and Toshia Wrenn
    Program: NSF TN-SCORE
    Research Project: Electrochemically Assisted Deposition of Indium Tin Oxide for Use in
    Poster: NSF REU Barclay Randall Poster.pdf
    Research Abstract:
    Indium tin oxide (ITO) was used as a hole conductor for quantum dot sensitized solar cells (QDSSC) and optimization of the deposition of ITO was investigated. To determine optimal voltage for electrochemically assisted deposition (EAD) of ITO, linear sweep voltammetry was employed. The results showed a cathodic voltage of 0.8V is an optimal voltage for the reactions needed to facilitate ITO deposition. To determine an optimal time for deposition of ITO, EAD of ITO was performed on multiple titanium foils for various times. The optimal time was determined to be around 300 seconds as determined by using scanning electron microscopy (SEM) to look at the morphology of the film deposited. QDSSCs were created by anodization of titanium to produce titanium dioxide nanotubes, nanotubes were sensitized by chemical-linking of cadmium selenide quantum dots, and EAD of ITO. Devices were subjected to EAD of ITO for 60s, 120s, and 300s. EDX of this device showed that there was significantly more indium and tin throughout the device area than either the 60 second or 120 second film, indicating that the 300s device has the largest active area. In agreement with the EDX findings, photovoltaic efficiency of these devices showed that the device that underwent EAD for 300s had the highest efficiency.

  • Sarah Robb - Biomedical Engineering, Robert Morris University

    Sarah RobbEducational Institution: Robert Morris University
    List of Mentors: Dr. Bridget Rogers, Dr. Greg Walker, and Bobby Harl
    Program: NSF REU
    Research Project: Mixed Fuel Combustion Synthesis of Yttrium Aluminum Garnet (YAG)
    Poster: NSF REU Sarah Robb Poster.pdf
    Research Abstract:
    Yttrium aluminum garnet (YAG) doped with cerium (Ce) fluoresces when irradiated by photons. Combustion synthesis is a common route to making YAG. Typically, a single fuel is used to produce YAG via combustion synthesis. Recently, optimization of combustion processes through using fuel mixtures has been studied. This project focuses on characterizing the properties of YAG:Ce1% combusted using a mixture of citric acid and urea in different fuel ratios.

    Citric acid is a chelating agent, which creates a well-distributed dopant solution during dehydration, and thus in the final product. Urea produces a high flame temperature during combustion, which crystallizes the YAG:Ce1% upon formation. We hope that by using a mixture of fuels, the combustion synthesis will produce crystalline YAG:Ce1% with a uniform dopant distribution.

    Photoluminescent spectroscopy (PL) and x-ray diffraction (XRD) were conducted on the resulting materials to determine the effect of synthesis conditions on the properties of the product. The PL compared the intensity of the fluorescence and XRD compared the crystal structure of the synthesized YAG:Ce1%. We have shown that mixing the fuels produces YAG:Ce1% with an overall lower PL signal than either pure fuel. We have also studied the effect of post-synthesis heat treatment on the PL intensity and crystal structure. Materials produced with pure urea have the highest PL intensities for all heat treatments studied. Urea also produces YAG:Ce1% with the best initial crystal structure. Combustion synthesis using fuel mixtures with increasing percentages of citric acid produces materials with decreasing crystallinity.

    • Sarah Robb presented her summer research at 2012 American Institute of Chemical Engineering Annual Symposium in Pittsburg, PA.
    • Sarah Awarded NSF Graduate Research Fellowship in 2014
  • Andrew Santos - Chemical Engineering, North Carolina State University

    Andrew SantosEducational Institution: North Carolina State University
    List of Mentors: Dr. Peter Cummings and Will French
    Program: NSF REU
    Research Project: Impact of Metal Type on the Deformation and Conductivity of Ultrathin Nanowires
    Poster: NSF REU Andrew Santos Poster.pdf
    Research Abstract:
    Metallic nanowires have shown potential to meet the demand of the miniaturization of electronics due to their promising structural and electrical properties. These properties can be classified in specific metals by straining nanowires. In this study, gold, platinum, silver, copper and aluminum nanowires were elongated with a constant applied tensile strain rate at 10 K and 298 K. Elongation was simulated using molecular dynamics with the second moment approximation of the tight binding potential. Different deformation modes, characterized by necking and slip planes, were exhibited in each metal. The different deformation modes were identified by an analysis of the stress-strain relationship, changes in the minimum cross-sectional area and visual inspection. For smaller nanowires, the conductance was shown to be strongly dependent on structural changes and impurities. Decreases in conductance up to 28% of the initial crystalline structure were caused by slip planes and twin boundaries; drastic changes of the structure were correlated with sudden changes of the conductance.

  • James Taylor - Chemistry, University of Maryland, Baltimore County

    James TaylorEducational Institution: University of Maryland, Baltimore County
    List of Mentors: Dr. Hak-Joon Sung and Tim Boire
    Program: NSF REU
    Research Project: Synthesis and Characterization of a New Class of Shape Memory Polymers for Development of “Smart” Vascular Constructs
    Poster: NSF REU James Taylor Poster .pdf
    Research Abstract:
    Current vascular stents, grafts, and patches for treating occluded or ruptured blood vessels associated with vascular diseases require open surgeries, which leads to cumbersome implantation and removal procedures. Through the development of a shape-memory polymers (SMPs) however, we hope to create minimally invasive ways to deliver vascular patches or stents through catheters or laparoscopes, which would make the procedure a lot more patient-friendly. Poly(ε-caprolactone) (PCL) is a thermoresponsive and biodegradable shape memory polymer that can be programmed into a specific shape at one temperature and return to its original shape at the melting point. In order to use PCL in physiological conditions, its melting point would have to be slightly less than 37 degrees C. The melting temperature should be tuned by copolymerizing with varying the molar ratio of carboxylated-PCL (cPCL). The polymer is currently being characterized by differential scanning calorimetry (DSC) for thermal properties; gel permeation chromatography (GPC) for degradation properties; dynamic mechanical analysis (DMA) for theromechanical (“Shape memory”) properties; and goniometry for surface properties. Preliminary results show promise in synthesizing this polymer with an appropriate melting point, suggesting its possible utility in creating non-invasive and biodegradable vascular therapeutics.

    • James Taylor presented his REU poster at the 2012 Annual Biomedical Research Conference for Minority Studetns in San Jose, CA.
    • Taylor was co-author on a poster presented at the 2012 Biomedical Engienering Society Annual Meeting in Atlanta, GA.

2011

  • Rebecca Cioffi - Materials Science, Rensselaer Polytechnic Institute

    Rebecca CioffiEducational Institution: Rensselaer Polytechnic Institute
    List of Mentors: Dr. Yaqiong Xu, Yunhao Cao, Tu Hong
    Program: NSF REU Program
    Research Project: Use of micromechanical exfoliation of bulk graphite and MoS2 to establish a graphene/MoS2 junction
    Poster: Rebecca Cioffi Student Poster.pdf
    Research Abstract:
    The goal of this study is to explore the properties of a graphene/molybdenum disulfide junction using photoconductivity measurements. To begin, micromechanical exfoliation via the scotch-tape method has been used to obtain monolayer and few layer thick flakes of graphene and MoS2. Optical and Raman microscopes have been used to determine whether the flakes are one atomic layer thick. Using the same cleavage process as for cleaving bulk graphite and MoS2, graphite and MoS2 will be cleaved simultaneously, creating a junction between the two single-layer flakes. This mixture will be deposited onto the SiO2/Si substrate. This will form a Schottky barrier between the graphene, a semimetal and MoS2, a p-type doped semiconductor. Electrodes will then be deposited connecting to both materials on the silicon wafer. Analysis of the electronic transport properties and photon-electron conversion of the graphene/MoS2 junction will allow for further research into the potential usage of such a device in photovoltaics, transistors, and optoelectonic devices.

  • Jonathan Clinger - Physics, Lipscomb University

    Jonathan ClingerEducational Institution: Lipscomb University
    List of Mentors: Dr. Kirill Bolotin, Hiram Conley
    Program: NSF TN-SCORE Program
    Research Project: Creating controllable strain in graphene
    Poster: Jonathan Clinger Student Poster.pdf
    Research Abstract:
    It has been predicted that a controlled distribution of strain in graphene can create a band gap in its density of states, which could potentially lead to multiple device applications of graphene in electronics. We developed two novel methods to induce strain in large-scale graphene grown by chemical vapor deposition. We demonstrated creation of uniaxial strain up to 0.5% by fabricating a device where a sheet of graphene is suspended between two gold supports and then controllably pulling the graphene down onto a third support. In a different approach, we induced a strain of 0.2% in graphene by depositing it onto a polymer that was then strained. The graphene can then be transferred onto an arbitrary substrate to enable greater flexibility in device design. We expect that the devices fabricated using these methods will allow us to investigate the influence of strain on electronic transport in graphene.

  • Justin Colar - Civil Engineering, Alabama A&M University

    Justin ColarEducational Institution: Alabama A&M University
    List of Mentors: Dr. Greg Walker, Dr. Rachael Hansel, Sarah Gollub
    Program: NSF-REU
    Research Project: Investigation of the Quenching Concentration of Europium in Photo Luminescent Lanthanum Zirconate
    Poster: Justin Colar Student Poster.pdf
    Research Abstract:
    Lanthanum Zirconate, La2Zr2O7 (LAZ) is commonly used within the aeronautics industry as a protective coating on the surface of gas turbine blades. The LAZ coating is used to protect the blades from the hot corrosive gases that are produced during the operation of a gas turbine. When LAZ is doped with europium (Eu) it can become a temperature sensor. This is done by beaming a wavelength of light to excite the electrons within the LAZ:Eu lattice, and as the electrons come back to down to the ground state they will give off energy in the form of photons. The time it takes for the electrons to come back down to the ground state is known as the decay time. Decay time is temperature dependent; therefore, the time it takes for the electrons to come down to the ground state is proportionate to the temperature. However, it is currently not known at what concentration of europium in LAZ will give the brightest intensity. The goal of this summer research project is to find out at what concentration of europium in LAZ will quench. This is possible by increasing the concentration of europium and then comparing the emissions spectra at different concentrations. This research will produce a higher intensity sensor that will be able to relay better results when trying to measure temperature.

  • Megan Dunn - Chemical Engineering, University of Arkansas

    Megan DunnEducational Institution: University of Arkansas
    List of Mentors: Dr. Craig Duvall, Dr. Hongmei Li, Brian Evans
    Program: NSF-REU
    Research Project: Delivery of an MK2 Inhibitor Utilizing Peptide Stapling
    Poster: Megan Dunn Student Poster.pdf
    Research Abstract:
    Coronary artery bypass grafting is an effective treatment for ischemic heart diseases, but long-term patency remains a significant problem. Recent studies have shown that greater than 45% of grafts experience failure in the first 18 months. Graft failure is primarily attributed to intimal hyperplasia, a pathological process in which vascular smooth muscle cells (VSMCs) migrate, proliferate, and deposit extracellular matrix into a neointima. MAPKAP kinase II (MK2) is an upstream regulator of heat shock protein 27 which has been shown to play a major role in the transition of VSMCs to the pathological, proliferative phenotype characteristic of intimal hyperplasia. Therefore, we hypothesize that successful inhibition of MK2 will prevent intimal hyperplasia and ultimately improve graft patency. A previous study has identified a peptide sequence, MK2i, which effectively inhibits MK2 at a concentration range of 8.1-134 µM. However, efficient intracellular delivery of the peptide emains a significant barrier. The overall goal of this project is to determine if peptide stapling can be utilized to enable intracellular delivery of the MK2i peptide. Peptide stapling uses a ring closing reaction to add a hydrocarbon “staple” to successive turns of an α-helix. Stapled peptides have increased helicity, potency, protease resistance and most importantly, cell permeability. The specific aim of this project was to determine if MK2i was a suitable candidate for peptide stapling and develop a protocol for the synthesis of the stapled MK2i peptide. Mk2i was synthesized using solid-phase peptide synthesis (SSPS) with Fmoc chemistry. Circular dichroism was used to assess secondary structure of MK2i in both water and trifluoroethanol which is known to induce α- helical secondary structure in peptides. The circular dichroism results showed that the peptide was 6% α-helical in water and 13% α-helical in trifluoroethanol. These findings suggest that MK2i may be a suitable candidate for peptide stapling. This hypothesis will be further tested by implementing the developed peptide stapling protocol to determine if stapled MK2i peptides showed increased potency, specificity and cell permeability for potential use as a therapeutic in coronary artery bypass grafting.

  • Elly Earlywine - Chemistry, Hope College

    Elly EarlywineEducational Institution: Hope College
    List of Mentors: Dr. Sandra Rosenthal, Emily Jones
    Program: NSF REU Program
    Research Project: Exploring Cytotoxicity of Silica Coated Water-Soluble CdSe Nanocrystals
    Poster: Elly Earlywine Student Poster.pdf
    Research Abstract:
    For this study, red-emission CdSe nanocrystals were prepared and their cytotoxicity was tested. In order for hydrophobic CdSe nanocrystals to be used in biological studies, they must be coated with a water soluble, nontoxic shell such as ligands, polymers, or silica. Using the standard pyrolysis of organometallic reagents, CdSe nanocrystals were prepared and coated with a silica shell by a reverse microemulsion method. UV-Visible absorption spectroscopy and transmission electron microscopy were used to determine the characteristics of the nanocrystals prepared. The CdSe nanocrystals were approximately 4.4nm in diameter. MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) colorimetric assay was performed in HELA cells to determine the cytotoxicity of the CdSe nanocrystals. Toxicity of the CdSe nanocrystals was compared to 605 ITK amino quantum dots (Invitrogen). As the assay exhibited, the CdSe quantum dots were more cytotoxic than the 605 ITK amino quantum dots. Improvements in the silica coated nanocrystals still need to be made before their cytotoxicity can be fully tested. Some of the nanocrystals were successfully coated in silica; however, a great deal of aggregation of both the nanocrystals and silica were observed.

    • Elly presented her summer research poster at the 2012 ACS National Meeting in San Diego, CA.
  • Stephen Filippone - Materials Science, Johns Hopkins University

    Stephen FilipponeEducational Institution: Johns Hopkins University
    List of Mentors: Dr. Florence Sanchez, Lesa Brown
    Program: NSF REU Program
    Research Project: Effect of C-S-H Coated CNFs on the Performance of Cement Paste
    Poster: Stephen Filippone Student Poster.pdf
    Research Abstract:
    Increasing the strength of cement can bring huge benefits to people and the environment. Research has been conducted on the incorporation of carbon nanofibers (CNFs) and carbon nanotubes (CNTs) into cement. CNTs and CNFs have properties desirable to make strong and durable cement composites. Although effective means of dispersing fibers in solution have been found, upon adding that solution to cement, the fibers re-agglomerate leading to cement pastes that do not exhibit large enough strength increases to be good composites. The goal of this study was to devise an effective means of preventing the re-agglomeration of CNFs in cement by coating them with synthetic calcium silicate hydrate (C-S-H) to help the fibers bond better with the cement matrix. An effective way to form C-S-H on the CNFs was first studied using both calcium oxide and silicon dioxide or calcium nitrate tetrahydrate and sodium meta-silicate pentahydrate. The calcium and silica salts were easier to react and were used in the cement pastes that were tested. It was found that the sonication time of the salts in solution affected the consistency of the cement paste. Longer sonication times led to more synthetic C-S-H formed and thicker cement paste that was difficult to pour, leading to a porous material. Less porous cement pastes were made by decreasing the sonication time. SEM coupled with EDS (energy dispersive X-ray spectroscopy) was used to characterize the coating of the CNFs with C-S-H and also the dispersion of the CNFs in the cement matrix. Compression and flexural strength test were conducted on the cement pastes after 24 hours, 3 days and 7 days.

  • Annalisa Fowler - Mechanical Engineering, University of Alabama, Huntsville

    Annalisa FowlerEducational Institution: University of Alabama, Huntsville
    List of Mentors: Dr. Jason Valentine, Joy Garnett
    Program: NSF REU Program
    Research Project: Maxwell Fisheye for Use as an Optical Cross Connect
    Poster: Annalisa Fowler Student Poster.pdf
    Research Abstract:
    The Maxwell fisheye lens is a non-homogenous, aberration free, perfectly focusing lens. This lens focuses light from a point source on the surface of the lens to another point on the opposite side. While the fisheye has been studied in the past for its application in imaging, here we extend its use for chip based photonics. Specifically, we are developing the lens for use as a massively parallel and low-loss optical cross-connect. Our study focuses on creating this lens in a silicon-on-insulator (SOI) architecture which is commonly used in optical circuitry because of its high refractive index contrast. A correlation can be found between modal refractive index and silicon waveguide height by using effective waveguide theory. With grayscale electron beam lithography and reactive ion etching (RIE), a gradient refractive index can be fashioned in the silicon by varying its height, allowing the non homogenous lens to be produced. An important part of this project was developing a precise RIE transfer process with low roughness and accurate pattern transfer from a lithographically defined pattern. This was done by varying the chemistry, power, and pressure of the etch. Based on this work the designed lens can now be fabricated and experimentally characterized for use in on chip photonics applications.

    • Annalisa Fowler co-authored a poster presented at the 2012 OSA Conference on Lasers and Electro-Optics/Quantum Electronics and Laser Science in San Jose, CA.
  • William "Reb" Kornahrens - Chemical Engineering, North Carolina State University

    William "Reb" KornahrensEducational Institution: North Carolina State University
    List of Mentors: Dr. Eva Harth, Benjamin Spears
    Program: NSF-REU
    Research Project: Synthesis and Characterization of Nanosponges for Drug Delivery and Brain Cancer Treatment
    Poster: William Kornahrens Student Poster.pdf
    Research Abstract:
    Degradable 3-D polyester nanoparticles, or nanosponges, have been receiving more attention for their potential biomedical applications. Conventional cancer treatments involve the use of drugs that are toxic to healthy cells as well as tumor cells. A more ideal form of treatment could be facilitated through the use of nanoparticles crosslinked with targeting units, such as peptides, that selectively recognize receptors on the surfaces of tumor cells. Unlike other delivery systems, nanosponges have the advantage of enabling a controlled, linear release of a large amount of drug over a long period of time. In addition, post modification strategies can be utilized to alter several properties of nanosponges, such as hydrophobicity, morphology, particle size, and functionality. We utilized two different linear copolymers for nanoparticle formation: one is poly( valerolactone-allylvalerolactone ) and the other is poly( valerolactone-allylvalerolactone –oxepanedione). These two linear polymers have different morphologies and will be investigated with future in vivo andin vitro drug release studies. In particular, temezolomide, a chemotherapeutic used to treat advanced brain tumors, will be encapsulated inside these nanoparticles and the rate of drug release will be measured with UV-visible spectroscopy. Furthermore, the nanoparticles will be labeled with a fluorescent dye in order to conduct biodistribution studies to determine if they are capable of crossing the blood-brain barrier.

  • Rory Locke - Physics, Middle Tennessee State University

    Rory LockeEducational Institution: Middle Tennessee State University
    List of Mentors: Dr. Sandra Rosenthal, Amy Ng
    Program: NSF TN-SCORE Program
    Research Project: Fabrication of hybrid TiO2-CdSe nano "matchstick" photovoltaic devices
    Poster: Rory Locke Student Poster.pdf
    Research Abstract:
    Sources of alternative energy continue to be a well-studied area of research across the globe. Solar power remains one of the best solutions for future energy requirements; however, low efficiencies and high cost of manufacture are limiting factors of silicon based solar cells. Semiconductor nanocrystal research has introduced many types of nanocrystalline photovoltaic devices,for instance, thin films of dispersed nanocrystals in a conductive polymer. While these devices have less than comparable efficiencies versus silicon-based devices, they remain a viable option for low cost/economically friendly solar cells. In this project, titanium dioxide (TiO2) nanorods were synthesized, and then a preferential growth of cadmium selenide (CdSe) nanocrystals onto the tips of the nanorods produced “matchstick” nanostructures. Once the desired size and shape of the nanostructures was obtained, electrophoretic deposition was used to align and attach the matchstick nanostructures to a glass/ITO substrate; the photovoltaic device was completed by thermally depositing an aluminum contact on top of the nanorods. Current-voltage curves with then be used to test the efficiency of the device.

  • Carl Merrigan - Physics, William Jewell College

    Carl MerriganEducational Institution: William Jewell College
    List of Mentors: Dr. Richard Haglund, Victor Diez Blanco, Joyeeta Nag
    Program: NSF REU Program
    Research Project: Laser Switching of Thin Films of Vanadium Dioxide
    Poster: Carl Merrigan Student Poster.pdf
    Research Abstract:
    Vanadium dioxide (VO2) undergoes a phase transition from a semiconducting state to a metallic state at a temperature of 68⁰C. This phase transition involves changes in the transparency, conductivity and crystal lattice structure of VO2. VO2 can be switched in several ways, including by heat, by an applied electric field, or by high-power laser irradiation. My project for the summer was to study the behavior of this phase transition in thin films of VO2 being heated by laser irradiation. In order to characterize this thermally induced phase transition, we built an optical pump-probe experiment. We tested three different pump lasers, including a 5 mW 1550 nm laser, an 80 mW 785 nm laser, and a 200 mW 532 nm laser. We also conducted computational simulations in Comsol Multiphysics 4.2 in order to model the laser-induced temperature rise in our samples. This research is a part of a long-term project to design and fabricate an optical switch using VO2. Such switches could eventually be used in high-speed photonic circuitry.

  • Geoffrey Musick - Biochemistry, Lipscomb University

    Geoffrey MusickEducational Institution: Lipscomb University
    List of Mentors: Dr. Yaqiong Xu, Yunhao Cao, Tu Hong
    Program: NSF TN-SCORE Program
    Research Project: Creating a junction between single layer graphene and single layer MoS2
    Poster: Geoff Musick Student Poster.pdf
    Research Abstract:
    The intent of this project is to create a junction between 2-dimensional graphene and MoS2for photovoltaic applications. First efforts have been made to mechanically exfoliate graphene and MoS2from their layer-by-layer bulk materials to SiO2/Si substrates using the scotch tape method. Moreover, optical and Raman microscopes have been used to identify and classify single or few layer graphene and MoS2. Once both samples are successfully cleaved down to the single layer, the goal is to create an overlap between the two single layers by placing a mixture of the two samples on scotch tape to create a single layer junction between two different materials. A Schottky barrier between metallic graphene and semiconducting MoS2will form in this junction. The nanoscale photon-electron conversion of this junction will be investigated via scanning photocurrent measurements.

  • Danna Sharp - Biochemistry, University of Tennessee, Knoxville

    Danna SharpEducational Institution: University of Tennessee, Knoxville
    List of Mentors: Dr. Kane Jennings, Gabriel Leblanc, Gongping Chen
    Program: NSF TN-SCORE Program
    Research Project: “Isolation and Deposition of Photosystem II onto Gold Electrodes”
    Poster: Danna Sharp Student Poster.pdf
    Research Abstract:
    Photosystem II (PSII) is a protein found in the thylakoid membranes of phototroph’s chloroplasts. It has the ability to collect energy from light and split water molecules to produce protons, electrons, and oxygen gas. Once an electron is released, it is then excited using solar energy and is passed on through the membrane to be used as an energy source for other cell processes. In this work, a procedure was developed to isolate PSII from spinach chloroplast membranes without the use of an ion exchange column. Oxygen activity was measured in solution using a platinum microelectrode with a Ag/AgCl reference in an airtight electrochemical cell. Different mediators were examined to optimize oxygen gas production. Finally, the isolated PSII proteins were immobilized on planar gold electrodes using self assembled monolayer techniques. The films were analyzed with ellipsometry, IR spectroscopy, and photochronoamperometry. Further research in the development of PSII films will enable the development of PSII bio-hybrid devices which utilize water as a preliminary electron source.

  • Scott Surles - Physics, Middle Tennessee State University

    Scott SurlesEducational Institution: Middle Tennessee State University
    List of Mentors: Dr. Sandra Rosenthal, Scott Neizgoda
    Program: NSF TN-SCORE Program
    Research Project: The Road to Air-Stable Quantum Dot Solar Cells by Way of 1,4-phenylene-bis(dithiocarbamate)
    Poster: Scott Surles Student Poster.pdf
    Research Abstract:
    By harnessing the power of the sun, the rapidly growing field of solar technology offers a great potential for a source of clean and renewable energy. Despite the multitude of possible light harvesting materials, solar cell technology has mainly relied on silicon for the past 60 years. In an effort to design a more low cost, highly efficient alternative to the traditional solar cell, our research implements lead sulfide nanocrystals as light harvesters. Semiconducting nanocrystals are promising candidates for photovoltaics because they offer size-tunable band gaps, notably high extinction coefficients, and facile colloidal synthesis. Traditionally, however, nanocrystals suffer from high amounts of photo-oxidation and electron-hole-pair recombination. In light of this, 1,4-phenylene-bis(dithiocarbamate) (PBDT) is investigated as a possible ligating species which has promise of not only facilitating electron transport due to being fully conjugated, but should also fully passivate the surface of the nanocrystals. This full passivation should render the nanocrystal more resilient to photo-oxidative effects, leading to more air stable devices. In this study, devices are tested routinely over a period of several weeks to monitor the effect that PBDT has on the lead sulfide nanocrystals.

  • Thomas Werfel - Engineering Physics, Murray State University

    Thomas WerfelEducational Institution: Murray State University
    List of Mentors: Dr. Craig Duvall , Dr. Hongmei Li, Brian Evans
    Program: NSF REU Program
    Research Project: "Proximity Activated" smart nanoparticle for the delivery of siRNA to metastatic tumor cells
    Poster: Thomas Werfel Student Poster.pdf
    Research Abstract:
    Permeability-glycoprotein (P-gp) over expression in breast cancer cells desensitizes the tumor to chemotherapeutics and can lead to the development of multiple drug resistance (MDR), significantly worsening patient survival. siRNA presents a powerful tool for silencing P-gp, but in vivo delivery barriers such as endosomal trafficking and off-target cytotoxicity must be overcome to make the treatment feasible. MMP-7 plays a significant role in tissue breakdown and cell migration, and its over expression is a hallmark of tumor progression into metastasis. In this study, an MMP-7 responsive peptide and polyethylene glycol (PEG) cloak were incorporated onto a previously designed smart polymeric nanoparticle (SPN) that contains a cationic corona for condensing siRNA and pH-responsive, endosomolytic core. The cationic corona of the SPN can trigger nonspecific cell uptake in normal tissues. The PEG cloak shields the positive surface charge of the SPNs until being cleaved in MMP-7 rich tumor environments, allowing “proximity activated” delivery of siRNA. “Proximity activated” SPNs were characterized by dynamic light scattering (DLS) and transmission electron microscopy (TEM) and have a diameter of ~80nm. Zeta potential measurements of the PEGylated SPNs showed a 3-fold increase in surface charge from 4.1 mV to 12.6 mV after being exposed to MMP-7 over time. Gel electrophoresis showed that the PEGylated SPN condensed siRNA effectively, and furthermore, flow cytometry confirmed MMP-7 dependent cytosolic delivery of siRNA. These results indicate the potential of this carrier design to improve tumor targeting and efficient delivery of siRNA designed to overcome MDR and re-sensitize breast cancers to standard chemotherapeutic regimes.

  • Jia Jia Zhang - Biomedical Engineering, Harvard University

    Jia Jia ZhangEducational Institution: Harvard University
    List of Mentors: Dr. Kane Jennings, Darlene Gunther
    Program: NSF REU Program
    Research Project: Deposition of Photosystem I onto Graphene for Photoactive Electrodes
    Poster: Jia Jia Zhang Student Poster.pdf
    Research Abstract:
    Thin film, bio-inspired systems utilizing the photoactive protein complex Photosystem I (PSI) hold great promise in advancing solar energy conversion technologies. Monolayer (~7nm) and multilayer (~700nm) films of PSI deposited on conducting electrodes exhibit photocatalytic capabilities when incorporated into electrochemical cells. In this project, I use a vacuum-assisted approach to rapidly assemble monolayer and multilayer films of PSI onto graphene, a one-atom thick carbon material that could one day become ubiquitous in the production of low-cost, transparent, and flexible electronic devices. Cyclic voltammetric experiments demonstrate that increasing PSI film thickness (from bare to monolayer to multilayer PSI) decreases electrode peak currents, confirming the additional adsorption of insulating material onto the surface of graphene. Further, photochronoamperometric measurements show that PSI-coated graphene electrodes exhibit a greatly amplified photoresponse, which varied with redox mediator used, in comparison to a control. Future work in the optimization of graphene-PSI interfaces could lead to improvements in the efficiency and cost of solar devices.

Synaptotagmin-1 (Syt-1) is a prominent synaptic vesicle protein and one of the Ca2+ sensors that triggers neurotransmitter release. Given the heterogeneity of the synaptic vesicle population and the associated variation of Ca2+ sensors, it is informative to study the distribution and mobility of individual Syt1-containing vesicles within live neurons. Quantum dots (Qdots), a.k.a. photo-luminescent semiconductor nanocrystals, possess superior optical properties ideal for single vesicle tracking. Their high quantum efficiency leads to a large signal-to-noise ratio and their photostability enables long-term tracking. Qdots were randomly tagged to single vesicular Syt-1 in live neurons via a highly selective monoclonal antibody; stimulation-induced synaptic vesicle turnover. After labeling, continuous fluorescence imaging of single Qdots was performed while neurons were continuously stimulated to induce vesicle release. Image stacks were processed in FIJI and single Qdot tracking trajectories were generated using the TrackMate plug-in.

We observed significant differences (>20%) between diffusion coefficients for stimulation vs. non-stimulation using antibody-conjugated Qdots. However, there was only a 6% difference in the mean diffusion coefficients between stimulation and another control - non-specifically uptaken Qdots. Looking further into this discrepancy, we noted that there was also a significant loss of Qdots over time during field stimulation (40%). Although the effect of activity is an important cornerstone of understanding vesicle mobility, results throughout the literature remain inconsistent. Given this information, we propose that a possible explanation for the discrepancies among the literature is that when vesicles release during field stimulation, Qdots are washed away after dissociating from the antibody in the acidic vesicular environment.  Future research directions involve combining Qdot imaging with dyes to specifically label synaptic vesicles, but this information holds the potential to impact the validity of results from previous findings using field stimulation.