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Physical Chemistry Seminar


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Surface Chemistry of Zinc Oxide
Nanoparticles: From Optochemical Sensing to Applications in
Fiber Technology
Zinc oxide nanoparticles have applications that range from catalysis to optoelectronics. The metal oxide is unique in that its surface is fairly reactive with respect to gas adsorption, and it
has a bimodal room temperature photoluminescence (PL) spectrum consisting of UV excitonic and surface defect-related visible emission peaks. A goal of our research has been to study how adsorption on the surface of ZnO nanoparticles affects their PL spectrum and to investigate the possibilities of monitoring adsorption for so-called “optochemical sensing” and gas filtration/ residual life indication applications. It has been found that physisorption causes reversible changes in the ratio of the UV and visible emission peaks, while chemisorption leads to dramatic irreversible changes in the ratio. Adsorbed hydroxyl groups, which act as charge traps and may be replaced by chemisorption of molecules such as sulfur dioxide and methanethiol, are found to play a key role in the PL changes. Experimental surface science studies, including X-ray
photoelectron spectroscopy measurements, have been accompanied by density functional theory (DFT) calculations to understand the surface chemistry that occurs and to correlate it with observed PL changes. A portable UV LED, two wavelength flurometer optimized for monitoring PL changes of metal oxide nanoparticles has also been constructed, and its applications have been demonstrated. Initial results will also be presented related to decorating the surface of polypropylene (PP) fibers and fabrics with reactive ZnO nanoparticles. Methods of achieving surface reactive ZnO will be discussed, including surface segregation of melt extruded ZnO/PP