Enhancing the Scope of Metal Oxide Nanoparticles via Doping and Plasmonic Coupling

Metal oxide semiconductors with a band gap between 2-4 eV are an important class of compounds in the electronics industry and for photocatalysis. As such, the demand for these materials is expanding rapidly. The fabrication of nano-sized metal oxide particles increases their cost-effectiveness by increasing the surface-to-volume ratio. Colloidal synthesis of nanoparticles also offers much greater control over morphology and grain size. However, most metal oxide nanomaterials suffer from an inability to utilize the majority of the solar spectrum, as well as from rapid electron-hole recombination of photo-generated charge carriers. The optical and electrical properties of these metal oxide nanoparticles can be improved by doping and by coupling with plasmonic noble metal nanoparticles. Doping metal oxides can change their band gap and induce a remarkable increase in conductivity. On the other hand, noble metal nanoparticles can strongly absorb light in the visible and near-infrared regions by virtue of localized surface plasmon resonance (LSPR) properties. This dissertation describes simple and reproducible procedures for the synthesis of uniform, monodisperse tin oxide (SnO2) and doped tin oxide nanoparticles, where the band gap and conductivity was successfully tuned by doping separately with antimony (ATO) and zinc (ZTO). This dissertation also details methods for reliable synthesis of LSPR-active gold nanoparticles (Au NPs) and gold-silver nanoshells (GS-NSs). These plasmonic nanoparticles are coupled with doped tin oxides as the shell in core-shell nanoparticles. This report also presents a unique way of synthesizing core-shell nanoparticles with TiO2 shells covering LSPR active GS-NSs; as well as core-dual-shell nanoparticles with either an insulating (SiO2) or semiconducting (SnO2) interlayer between the GS-NS and TiO2 shell. All these composite nanoparticles exhibit strong, tunable absorption in visible to near-infrared regions. These core-shell nanostructures also show a near-complete suppression of electron-hole recombination in the TiO2 and doped tin oxide shells. This report also presents a simple spin-coating method to fabricate uniform films on various substrates, starting with the aforementioned pre-synthesized colloidal metal oxide nanoparticles. These carefully designed metal oxide structures can be very effective in creating well-controlled systems for photocatalysis, solar cells, sensors, optoelectronics, multi-layered devices, and for the treatment of air and water pollutants.Chemistry, Department o