Date of Award

Summer 2011

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Graduate Group

Chemistry

First Advisor

Christopher B. Murray

Abstract

The aim of this dissertation is to understand the molecular chemistry of nanomaterials and to correlate their structures to their functions. The first part of this dissertation explores how we can use precursor chemistry to develop a synthetic approach to novel structures of nanomaterials. There will be a demonstration of morphology control in lead chalcogenide nanocrystals following an investigation of the precursor chemistry which gives valuable information on precursor decomposition during the crystal growth. At the same time, there will be a discussion about how we can understand structure-dependent properties of nanomaterials using advanced spectroscopic techniques. Well-established synthetic approaches discussed in the first part allow for the study of morphology-dependent optical properties of lead chalcogenide nanocrystals, including the shape-dependent electronic level structure of lead chalcogenide nanomaterieals and the symmetry-dependent phonon modes of lead chalcogenide nanocrystals.

For the second part of this dissertation, I will address the importance of ligand and surface chemistry of colloidal nanomaterials. New ligand systems will be introduced which allow a variety of interesting studies in chemical, optical, and electrical analyses of nanomaterials. Especially flexible electronic devices using low temperature process of thiocyanate chemistry will be demonstrated for lead chalcogenide nanomaterials to show promising opportunities of these ligand systems. For the electronic transport in a 1-dimensional confined system, NWs-based field-effect transistors are studied with post-processed surface treatment. Investigating the role of chemical treatment reveals how the surface/interface chemistry of NWs affects the electronic tranposport in 1-dimensional confined nanostructures.

To sum up, this dissertation first focuses on the molecular chemistry of nanostructures to help understand the synthesis and ligand/surface chemistry of nanomaterials. This understanding then enables us to study the optical and electric properties of these materials with various morphologies and assembled structures. With the ability to control the size, shape, and composite materials of the individual building blocks, I hope this dissertation can aid in the formation of collective ensembles with tunable material properties and structures. The ultimate goal is the creation of nanomaterial-based devices with programmable performances.

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