An Investigation of Solutions of Sulfur in Oleylamine by Raman Spectroscopy and Their Relation to Lead Sulfide Quantum Dot Synthesis

Undergraduate Honors Thesis

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Citeable URL: https://scholar.colorado.edu/concern/undergraduate_honors_theses/s7526c82v

Abstract

The first Raman spectrum of oleylamine was obtained after a multistep purification procedure based on acid-base chemical exchange techniques. The purification was needed because commercially available oleylamine shows photoluminescence in the Raman spectrum, obscuring the Raman peaks. Using the purified oleylamine, sulfur in oleylamine solutions were studied by resonance Raman, UV-vis, absorbance, NMR, and IR spectroscopy. Additionally, the time dependence of sulfur species present in these solutions was studied over several days using Raman spectroscopy. Based on the changes in the Raman spectra over time, it is hypothesized that the concentration of the polysulfide species S₄^2- increases, while the polysulfide species S₆^2- decreases over time in solutions of sulfur in oleylamine. Based on UV-vis spectra of lead sulfide quantum dots synthesized with sulfur in oleylamine precursor that was aged for different times, it is suggested that when a solution of sulfur in oleylamine is used as a precursor for the synthesis of lead sulfide quantum dots, it is best used within a few hours of preparation in order to minimize the absorption linewidth of the quantum dot 1S-1S transition (the lowest lying electronic transition). Spectroscopic information about the sulfur species present in sulfur oleylamine solutions during the first few hours and at later times is further discussed.

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