UC Irvine

Fabricated noble metal-loaded TiO2 nanoparticles situated on highly oriented pyrolytic graphite have been studied for photocatalytic enhancement and surface enhanced Raman spectroscopy properties. Plasma treating the HOPG surface results in an increase of TiO2 nanoparticle population. This increases the number of noble metal nucleation sites as well as increasing the likelihood for organic molecules to chemisorb on metal surfaces for molecular detection. High resolution characterization can be made to observe changes in surface morphologies of specific nanoparticles before and after experimentation.

Platinum nanoparticles deposited onto TiO2 substrates were analyzed for photocatalytic efficiency by Methylene Blue (MB) photodegradation. Various Pt morphologies on TiO2 were fabricated to determine photodegradation in relation to Pt surface area coverage. Pt morphologies ranged from individual Pt nanoparticles, partially encapsulated TiO2 particles, and completely encapsulated Pt-TiO2 (Noted as Small, Medium, and Encapsulate). Individual Pt nanoparticles (Small) on TiO2 were found to be the most efficient in photodegradation with the highest rate constant compared to low surface area coverage (k/SA).

Ag-TiO2 nanoparticles were fabricated in order to observe surface enhanced raman phenomena (SERS) with adsorbed thiophenol molecules. These particles were fabricated by coating the substrate in Ag precursor salt and irradiating the surface with UV light. Raman microscopy was used to determine signal intensity of adsorbed thiophenol. Signal enhancement was quantified by an enhancement factor (EF) calculation of ~10^5 in magnitude.

Bi-metallic loaded TiO2 nanoparticles were fabricated via sequential photodeposition. Initial attempts at fabricating distinct Pt and Au nanoparticles on TiO2 were made, however other methods need to be considered as Pt/Au-TiO2 were encapsulated by opposing metal material. Ag-Pt-TiO2 nanoparticles were fabricated by utilizing the Ag substrate coating method after Pt nanoparticles were photodeposited. Scanning electron microscopy reveals Ag nanoparticles forming alongside Pt nanoparticles adsorbed onto TiO2. SERS studies were performed on these particles to determine Ag antenna capabilities for enhancing nearby molecules adsorbed on Pt. Cyclohexene was used as a probe molecule that binds exclusively to Pt surfaces and dehydrogenates into benzene near room temperatures. Benzene signal was observed on Ag-Pt-TiO2 surfaces and an EF of ~10^4 was observed.