Heterostructures Prepared by Surface Modification of Nanocrystals
Lee, Bo Hyun
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Permalink
https://hdl.handle.net/2142/82864
Description
Title
Heterostructures Prepared by Surface Modification of Nanocrystals
Author(s)
Lee, Bo Hyun
Issue Date
2009
Doctoral Committee Chair(s)
Shim, Moonsub
Department of Study
Materials Science and Engineering
Discipline
Materials Science and Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Materials Science
Language
eng
Abstract
Inorganic nanocrystals (NCs) have drawn the attention from many researchers due to their promising potentials for next generation technologies, from photovoltaics to biological applications. Various types of NCs have become available by synthetic protocols developed in the last two decades. In addition, multicomponent hybrid NCs which can be expected to exhibit novel and unique properties from collective interaction between components have been reported recently. Despite this progress in the preparation of nanoscale materials, developing efficient and reliable ways of assembling/patterning NCs into ordered structures to utilize their potentials still remains a challenge. Controlling surface moieties of individual NCs may be one of the most effective methods to tailor surface properties of particles to be compatible with other surrounding phases (e.g. polymer or metal oxide) that may be necessary and thus leading to robust and ordered NC assembly. In addition, anisotropic surface functionalities on multicomponent hybrid NCs may lead to functional NC heterostructures with single particle precision. Here, we present NC-based heterostructures achieved from surface modified NCs. Surfactant bilayers formed around NCs have allowed hydrophobic NCs to be transferred into aqueous phase as well as facilitating formation of NC heterostructures via polymerization or sol-gel reaction. Coincidence lattice mismatch and surface functionality effects of metal oxide seed particles have been examined for formation of metal oxide-Au heterostructures by direct growth of Au NCs. Based on studies of surface cap exchange reaction of single component NCs, Au-Fe3O4 heterodimers have been asymmetrically surface modified to utilize coalescence of small Au particles to bring together different types of nanostructures. With coalesced Au bridges as interconnects, hybrid NC-based higher order structures have been achieved. The configuration of coalesced structures exhibits steric hindrance limited assembly. Upon asymmetric surface modification, reactive Au in heterodimers adsorb on Au nanorod (NR) surface and coalesce into ordered, plasmonic NC-based heterostructures.
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