| Nanocomposites combine the merits of two or more nanomaterials and their development is a rapidly growing field. Two inorganic materials, SiO2 and TiO2, have long served as adaptable nanomaterials due to their non-toxic properties, low cost, high thermal and chemical stability. The goals of the research reported in this dissertation were to develop some novel nanocomposites based on these two nanomaterials, and to test their applications in environmental analysis and energy-related catalysis.;Silica-supported Pt and Pt/Ru nanocatalysts were prepared using a template synthesis and applied in a direct methanol fuel cell. Various techniques such as EDS, TEM, XRD, UV-vis, and electrochemical measurements (i.e., cyclic voltammetry and electrochemical impedance spectroscopy) were conducted to characterize the catalysts and to demonstrate their electrochemical behavior for the methanol electro-oxidation reaction. Amphiphilic silica-encapsulated magnetic nanoparticles, modified with carboxyl and octadecyl hydrocarbon groups, were prepared using a sol-gel approach and applied for the detection of trace lead in water samples. The magnetic nanoparticles featured large adsorption capacities, strong magnetic response, and high precision in the analysis. Anodic stripping voltammetry and atomic absorption spectroscopy were used as the main characterization tools for the adsorption analysis.;Developed TiO2-based nanocomposites included silica-supported TiO2 nanocatalysts and Au nanowires/TiO2 film. In the former case, the nanoscale effect of a silica substrate on the formation and catalytic activity of TiO2 was investigated using TEM, XRD, TG-DTA, UV-vis and photo-catalyzed gaseous methanol oxidation system. The results showed that the size of the silica support played a crucial role in regulating TiO2 crystal size, thermodynamic properties, band gap, and catalytic activity. A nanoscale curvature model was proposed to explain the silica size effect. In the latter case, a facile route was developed to directly grow Au nanowires on a TiO2 film. The formation reaction and controlling factors on the formation of Au nanowires were investigated. This Au nanowires/TiO 2 film was integrated in a photoelectrochemical cell. Using water-splitting as a model reaction, this nanocomplex film generated 10 times higher photocurrent than a plain TiO2 film at an open circuit potential. |
