Nanoparticle engineering: Fiber coatings and photocatalysis

The focus of this research is the controlled synthesis of dendritic fibers for chromatography and titania particles for photoassisted destruction of organics. Aerosol processes are used and the effect of synthesis parameters on the properties of these materials is investigated.; Silica particles synthesized in flames are highly aggregated, have primary particle size usually in the range 5-50 nm, and thus, have high specific surface area (200-300 m{dollar}sp2{dollar}/g). Deposition of these ultrafine particles on silica fibers (1{dollar}mu{dollar}m) used in chromatography resulted in fiber surface area enhancement up to 20 times. The particles formed irregular structures in a dendritic fashion. Coagulation and sintering greatly determined the morphology and surface area of those dendrite-like structures. Using ferrocene as iron additive in the flame resulted in further surface enhancement (up to 23 times) of the fibers. Silica aggregates produced in the ferrocene-doped flame consisted of smaller primary particles and had higher specific surface area compared to aggregates collected from iron-free flames. The effect of the ferrocene additive on the properties of silica strongly depended on the mixing of the reactants in the flame. Sol-gel processes provide the capability of producing particles or films of controlled characteristics. Coating of fibers in silica sols of different chemical compositions provided surface area enhancement up to 6 times. Chromatographic columns packed with fibers coated in polymeric sols resulted in higher pressure drop compared to that of fibers coated in particulate silica sols.; The flame synthesis of ultrafine titania with controlled photocatalytic properties was also studied. The effect of flame variables on the specific surface area and phase composition of the powders was investigated. The photoassisted oxidation of phenol and salicylic acid under near-ultraviolet radiation (300-400 nm) was studied in aqueous titania suspensions. The photocatalytic activity of the flame-made titania was compared with that of commercial titania and was related to the preparation conditions.