Document Type

Thesis

Date of Award

5-1-2001

Keywords

Nanoparticles, Nanostructured materials

Degree Name

Chemistry (BA, BS)

Department

CHEMISTRY

First Advisor

Chuan-Jian Zhong

Second Advisor

M. Stanley Whittingham

Third Advisor

David C. Doetschman

Abstract

The study of nanoparticles is an emerging field of nanoscience and nanotechnology. A challenging issue is how deliberate tailoring and processing of the nanoscale materials can lead to well defined and functional nanostructures. In this thesis, we explore new strategies of nanoscale design and processing to address the challenge.

A core-shell chemical processing route towards fabrication of functional composite nanomaterials with defined sizes, shapes, compositions and surface properties is demonstrated. New findings of an investigation of thermally-activated core-shell reactivities of nanoparticles in solutions are described. Gold nanoparticles of ~2-nm core size with thiolate monolayer encapsulation were chosen as a model system for delineating design and processing parameters. We have demonstrated a remarkable evolution of the preformed particles in solutions towards monodispersed larger core sizes (5~10 nm) with well-defined shape and facet morphologies. The particles thus evolved were encapsulated with the thiolate shells, and exhibited striking propensities of forming long range ordered arrays.

While temperature driven crystal growth is known for bare particles, the evolution of the encapsulated nanoparticles in solutions into well-defined morphologies represents an intriguing pathway for size and shape control. It is further demonstrated that solution-annealing treatment in the presence of encapsulating thiols could lead to highly monodispersed nanoparticles. Insights into shell desorption, core coalescence and shell re-encapsulation have been provided by detailed examination of evolution temperature, thiolate chain length and core alloy composition. TEM, FTIR, UV-Visible, XRD, techniques were utilized for morphological and structural characterizations. The implication of our findings to the development of abilities in chemical processing nanoparticle size, shape and surface properties is also discussed.

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