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Dissertation Defense: Alexandra Koziel, Chemistry

Posted by on Tuesday, February 13, 2024 in Events, News.


Alexandra C. Koziel, Chemistry
*under the direction of Janet Macdonald

“Think Smaller: Understanding Selenium Pathways in Metal Chalcogenide Nanocrystal Synthesis

03.07.24  |  2:00PM CST  |  512 Light Hall

As nanochemistry grows as a field and the applications of nanomaterials emerge, the importance of understanding what happens in the reaction flask during synthesis—thinking smaller than the nanoscale level to the molecular level—has never been more important. Being able to track how the precursors are decomposing and affecting the resulting metal chalcogenide phase leads to more predictable and reproducible nanoparticle syntheses. The following dissertation outlines three mechanistic studies tracking selenium in the production of metal selenide nanoparticles. Diselenides were thoroughly investigated as they are important precursors in synthesizing metstable phases in nanochemistry. First, five hypotheses were explored for why diselenides experience much larger thermal movement in their chemical shift compared to monoselenides or selenols, including 1) rapid equilibrium to an isomer, 2) temperature dependent solute-solute interactions, 3) shielding, 4) solvent effects, and 5) molecular twisting. Second, molecular pathways from diselenide precursors to all eight copper selenide phases were tracked and two mechanisms were proposed—a Chan-Lam like and hydrogen peroxide like mechanism. Finally, tunable selenoureas and a combination of solvents were explored in the synthesis of iron selenides. Mechanistic deconvolution is still in progress. Ultimately, this dissertation shows progress towards a mechanistic toolbox that can be applied when uncovering pathways in nanoparticle syntheses of metal selenides.


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