Schematic of Electrophoretic Deposition of Colloidal Nanocrystals

Conductive

Electrodes

 

NC suspension

 

Department of Physics and Astronomy

Europium oxide Nanocrystals    EPD Europium oxide Nanocrystals    EPD

Europium sulfide Nanocrystals    EPD Europium oxide Nanocrystals    EPD

Europium oxide Nanocrystals    EPD Europium oxide Nanocrystals    EPD

Europium sulfide Nanocrystals    EPD Europium oxide Nanocrystals    EPD

 Europium oxide Nanocrystals    EPD Europium oxide Nanocrystals    EPD

Europium sulfide Nanocrystals    EPD Europium oxide Nanocrystals    EPD

Europium oxide Nanocrystals    EPD Europium oxide Nanocrystals    EPD

Europium sulfide Nanocrystals    EPD Europium oxide Nanocrystals    EPD

Europium oxide Nanocrystals    EPD Europium oxide Nanocrystals    EPD

Europium sulfide Nanocrystals    EPD Europium oxide Nanocrystals    EPD

Rare earth nanocrystal    EPD Europium oxide Nanocrystals    EPD

Rare earth nanocrystal    EPD Europium oxide Nanocrystals    EPD

Rare earth nanocrystal    EPD Europium oxide Nanocrystals    EPD

Rare earth nanocrystal    EPD Europium oxide Nanocrystals    EPD

Rare earth nanocrystal    EPD Electrophoretic deposition    EPD

Rare earth nanocrystal    EPD Electrophoretic deposition    EPD

Rare earth nanocrystal    EPD Electrophoretic deposition    EPD

Nanocrystal Electrophoretic deposition    EPD nanocrystals

 nanocrystals  Electrophoretic deposition    EPD

Electrophoretic deposition    EPD Electrophoretic deposition    EPD

Electrophoretic deposition    EPD Electrophoretic deposition    EPD

Electrophoretic deposition    EPD Electrophoretic deposition    EPD

Electrophoretic deposition    EPD Electrophoretic deposition    EPD

Electrophoretic deposition    EPD nanocrystals

Electrophoretic deposition    EPD nanocrystals

Electrophoretic deposition    EPD nanocrystals

Electrophoretic deposition    EPD nanocrystals

 nanocrystals Electrophoretic deposition    EPD nanocrystals

 nanocrystals Electrophoretic deposition    EPD nanocrystals

Some of Our Research Interests

Optical & Magnetic Properties of Nanocrystals and Nanocrystalline Thin Films:

My group’s current research can be divided into two thrusts: one focusing on thin film deposition of semiconducting heterostructures for optical structure fabrication, and one focusing on the synthesis of novel nanocrystals for magneto-optical and/or spintronic applications.  Currently, we are investigating three groups of nanocrystals: II-VI semiconducting nanocrystals (CdSe and CdTe), lanthanide chalcogenide nanocrystals (EuS & EuO) and lanthanide oxide nanostructures (Eu₂O₃, Tb₂O₃, etc.).  Cadmium selenide is, perhaps, the best known and most widely employed colloidal nanocrystal, as it is relatively easy to synthesize and its optical properties are robust and well characterized.  Europium chalcogenides (EuO, and EuS) have received similar attention, particularly europium oxide due to its luminescence-enhancing properties and EuS, due to its intriguing magnetic properties.  Eu₂O₃ particles have been employed heavily as phosphors in most television screens ever produced.

Such interest in these nanostructured materials lies in their possible use as constituent building blocks for nanostructured films and, in the case of the europium-based material, their use as optical and magneto-optical materials.  Currently, we are investigating how the size and the arrangement of different europium chalcogenides.   can affect the apparent (magneto-, electro-) optical properties of the material.  We have synthesized Eu₂O₃ nanocrystals and nanospindles, with the intention to produce nanowires and nano-ribbons.  We also are investigating the deposition of thin films of nanostructures, suspended in solution, through a variety of methods, including electric-field assisted film deposition.  How bi-layers of dissimilar colloidal materials, particularly CdSe and CdTe, can be deposited controllably in a site-selected format will be integral to our development of nanoscale devices.  Such a pursuit would lead to the assembly of nanoscale heterostructures, consisting solely of nanocrystalline materials.

Growth of Nanocrystalline Thin Films

Creation of nanoscale opto-electronic devices requires a different approach to the assembly of the associated structures from that of the common epitaxial methods, molecular beam epitaxy (MBE) and metal-organic chemical vapor deposition (MOCVD).  Use of nanocrystals to produce semiconductor thin films or to fabricate individual crystals for nanoscale devices has garnered substantial attention recently.  Although some research on nanocrystals focuses on individual crystals for devices (single-photon emitters, for example), our interests exist in device construction from dots, wires, ribbons, and thin films of these objects.  The more common methods of producing films of nanocrystals are dry casting and spin casting.  Both techniques involve films that are produced as the solution in which the crystals are suspended evaporates.  Although effective in producing films, neither provides adequate control over the film thickness or over the orientation of the individual nanocrystals in the film.

A recently developed technique, electrophoretic deposition of nanocrystals (EPD), exhibits great promise to control these parameters.  Electrophoretic deposition, also called simply electrophoresis, involves the translation of charged particle, suspended in solution, due to an ambient dc electric field.  A similar phenomenon, dielectrophoresis involves the locomotion of charged, dipolar, or polarizable objects, also suspended in a fluid, due to ac or a gradient electric field.  We incorporate aspects of both of these phenomena to yield electrophoretic deposition, which uses dc and gradient (fringe) electric fields to translate charged, dipolar, and polarizable nanostructures onto conducting substrates.

One of the positive aspects of electrophoretic deposition is the control over the deposition rate and, hence, deposition thickness for a certain material.  Also, a positive characteristic of electrophoretic deposition is the selectivity of the deposition site, due to electrode selection.  This means that film deposition only occurs at sites across which a voltage is applied.   Thus, floating or unbiased conducting electrodes yield no colloid deposition. 

Our interest is to observe the deposition of these nanocrystals in densely-packed arrays.  We believe that if these arrays also contained ordered, unidirectionally aligned nanocrystals, that very interesting, novel materials could be realized.