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He, Weidong
Ph.D. in Interdisciplinary Materials Science, May 2012

Research Information

Ph.D. Thesis Title
Ultra-Small Nanocrystals: Synthesis, Optical and Magnetic Properties, Oriented Attachment, and Film Assembly

Ph.D. Thesis Advisor
James Dickerson, Physics and Astronomy

Ph.D. Committee Members
Timothy Hanusa, Chemistry
Jason Valentine, Mechanical Engineering
Kalman Varga, Physics


Abstract. This dissertation focuses on the colloidal synthesis, and size-dependent optical & magnetic properties of several nanocrystals, such as EuX (X=O, S, Se, Te), Eu2O2S, and Te nanoparticles and nanorods. Significant Néel temperature enhancement and diamagnetic-magnetism transition were observed in EuTe and Eu2O2S nanocrystals, respectively. To better control the synthesis and improve the properties of these materials, the reaction kinetics and growth mechanism of EuS nanocrystals were evaluated using our newly-derived analytical expression for van der Waals interaction between a growing nanorod and an attaching nanoparticle. Towards the application of these nanocrystals, the synthesized nanocrystals were deposited into uniform nano-films using an automatic electrophoretic deposition technique.

Selected Publications

Superantiferromagnetic EuTe nanoparticles: room temperature colloidal synthesis, structural characterization, and magnetic properties. He, WD; Somarajan, S; Koktysh, DS; Dickerson, JH, NANOSCALE, 3, 184-187 , (2011)

Thermally driven isotropic crystallinity breaking of nanocrystals: Insight into the assembly of EuS nanoclusters and nanorods with oleate ligands. He, WD; Dickerson, JH, APPLIED PHYSICS LETTERS, 98, 081914 , (2011)

EuS nanocrystals: a novel synthesis for the generation of monodisperse nanocrystals with size-dependent optical properties. Koktysh, DS; Somarajan, S; He, W; Harrison, MA; McGill, SA; Dickerson, JH, NANOTECHNOLOGY, 21, 415601 , (2010)

Vanderbilt University