Nanoparticles generated by UV-irradiated gas phase photonucleation

Vapor phase synthesis is a versatile technique for creating nanostructured materials with potentially useful properties. In this dissertation, a systematic investigation is initiated to use UV-irradiated gas phase photonucleation to generate particles from transition metal carbonyl vapor precursors. Nickel (Ni), polymorphic iron (Fe) and nickel-iron bimetallic (FeNi{dollar}sb{lcub}rm x{rcub}){dollar} nanoparticles have been produced using an XeCl excimer laser (308 nm). Particle generation under a variety of UV-irradiation, background gas and pressure conditions is investigated. The structure and morphology of these particles and their aggregates are characterized by transmission electron microscopy (TEM) and X-ray diffractometry (XRD). Qualitative dependence of nanoparticle structure, size and morphology on processing conditions are studied. UV intensity is determined to be a key parameter.; Select hydrocarbon reactions and Fischer-Tropsch synthesis are used to probe the chemical reactivity of the particles. Observations of high reaction rates and extraordinary resistance to deactivation are described for ethane {dollar}rm (Csb2Hsb6){dollar} hydrogenolysis and CO hydrogenation catalyzed by Ni nanoparticles. Fe nanoparticles containing both fcc {dollar}gamma{dollar}-phase and {dollar}bcc alpha{dollar}-phase show high reactivity comparable to that of supported amorphous iron catalyst in CO hydrogenation. Ni nanoparticles are found to be more active than reduced nickel powders in catalytic propane {dollar}rm(Csb3Hsb8){dollar} cracking. Furthermore, bimetallic FeNi{dollar}sb{lcub}rm x{rcub}{dollar} nanoparticles have enhanced CO conversion rates compared to single component Ni and Fe nanoparticles in CO hydrogenation catalysis. Possible explanations for these unusual catalytic properties of nanoparticles and their formation are discussed.; Photoinduced nucleation (PIN) experiments using CS{dollar}sb2{dollar} and CS{dollar}sb2{dollar}/ethanol vapors have been carried out in a flow photochemical reactor. Following ultraviolet irradiation of the CS{dollar}sb2{dollar} containing vapors, photoinduced nucleated particles are captured and characterized using mass spectrometry and Raman spectroscopy. Results of the analysis confirm the presence of S{dollar}sb8{dollar} molecules in the particles produced by PIN of CS{dollar}sb2{dollar} vapor. The role of sulfur in the PIN mechanism is discussed in the context of these particle characterization results and the gas phase photochemistry of CS{dollar}sb2.{dollar}...