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Dissertation/Thesis Abstract

Synthesis of Lead Sulfide Nanocrystals and Their Two-Dimensional Electronic Spectra in a Spinning Cell
by Baranov, Dmitry, Ph.D., University of Colorado at Boulder, 2017, 254; 10618212
Abstract (Summary)

This thesis describes new aspects of the synthesis and ultrafast spectroscopy of PbS nanocrystals. The first part of the thesis investigates two aspects of PbS nanocrystal synthesis: the identity and composition of oleylamine reagent and the nature of sulfur species in sulfur solutions in long-chain amines. Oleylamine, formally cis-9-octadecyl-1-amine, is a solvent, a reactant, and a ligand in the synthesis of high-quality PbS nanocrystals and other nanomaterials. It is shown that commercial oleylamine samples contain elaidylamine, trans-9-octadecen-1-amine. Sulfur solutions in long-chain amines (n-octylamine and oleylamine) are common precursors in metal sulfide nanomaterial synthesis. Resonance Raman experiments on sulfur-amine solutions established the presence of various polysulfide anions, which slowly equilibrate on the timescale of days, causing a change in reactivity of the sulfur precursor. This aging of sulfur-amine solutions is shown to be strongly correlated with irreproducibility in PbS nanocrystal syntheses.

The second part of the thesis deals with non-linear optical experiments on sensitive samples, where vibrational stability, repetitive excitation, and sensitivity to air and moisture constitute a set of challenges often preventing an experiment without photoproduct contamination. As a solution to this problem, we designed, constructed and characterized a compact spinning sample cell suitable for liquid and thin film samples. The spinning sample cell, enclosed in a copper gasket sealed enclosure, enables complete sample exchange in optical experiments with up to 100 kHz repetition rates while maintaining an oxygen and water free environment at the 1 ppm level for over a month. The spinning sample cell was successfully used in a two-dimensional electronic spectroscopy experiment on PbS nanocrystals in solution, eliminating the buildup of the long-lived photoproducts and reducing trap emission in the spinning sample.

Indexing (document details)
Advisor: Jonas, David M.
Commitee: Damrauer, Niels H., Dukovic, Gordana, Nozik, Arthur J., Rogers, Charles T.
School: University of Colorado at Boulder
Department: Chemistry
School Location: United States -- Colorado
Source: DAI-B 79/01(E), Dissertation Abstracts International
Subjects: Physical chemistry, Nanoscience, Materials science
Keywords: Nanocrystals, Oleylamine, Repetitive excitation, Sample cell, Sulfur, Two-dimensional spectroscopy
Publication Number: 10618212
ISBN: 978-0-355-23231-8
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