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Date of Award
Stephanie L. Brock
The thesis study was focused on developing stable metal chalcogenide QD assemblies with robust links to harness their interfacial properties in a variety of applications (i.e., catalysis, sensing, and imaging). Oxidatively assembled metal chalcogenide QD systems are prone to disassemble in reducing chemical environments. To address the redox instability problem, oxidized dichalcogenide linkers produced by oxidative gelation were modified using the oxidative addition reagent Ni(1,5-COD)2 to produce redox innocent 2-D and 3-D QD assemblies. Although some Ni incorporation and improved redox stability were observed, the nature of the Ni speciation is not clear, and the process remains unoptimized. As an additional approach to effectively control the amount of oxidative addition reagent introduced during an experiment, quantification of diselenide linkers present per mg of CdSe aerogel was explored using a phosphorus containing reducing agent (TCEP) with the reaction followed by 31P NMR studies. However, the calculations revealed significant errors in concentration determination and formation of TCEP=O as a byproduct by a reaction path that remains undetermined. PbS QD assemblies are of interest for sensing, radiation detection, and other energy related processes. Another study tested the potential of obtaining PbS assemblies for NO2 gas sensing using oxidative assembly or electrogelation. However, due to inherent stability issues in the thiolate capped QDs and the poor kinetics associated with the cubic crystal phase intrinsic to PbS QDs, films were challenging to prepare. Electrochemically formed QD films from a sulfide capped PbS QD sol in water underwent composition changes/oxidation with the applied potential. Another aim of the thesis study was to explore the methods to utilize PbS QDs in a Si matrix to design X-ray radiation detectors for medical CT systems. A variety of deposition methods were examined to obtain better filling and adherence of QDs in a porous Si matrix. However, only 40-60% pore filling could be obtained and the PbS QDs were poorly adhered to the silicon substrate.
Mawella Vithanage, Lalani Pathmakumari, "Metal Chalcogenide Nanoparticle Systems: Towards Stable Assemblies And Applications In Imaging And Sensing" (2021). Wayne State University Theses. 833.