Aerosol synthesis and surface functionalization of luminescent silicon nanoparticles, aerosol synthesis of magnetic nanoparticles, and kinetic Monte Carlo simulation of silicon nanoparticle nucleation

The primary accomplishment of the research presented in this thesis is the development of a technology to produce light emitting silicon nanoparticles in macroscopic quantities by gas phase laser-driven pyrolysis of silane and post etching treatment. Theoretical exploration of the homogenous gas phase particle nucleation during pyrolysis of silane is another parallel focus of this thesis.; Production of nano-scale materials by CO₂ laser-driven gas phase reactions has been studied by several groups during the past two decades. The particle sizes can be controlled to below 10 nm. Although the silicon nanoparticles that are produced by this method are not photoluminescent, we have discovered that etching these particles with HF/HNO₃ mixture can controllably reduce their size and passivate their surface such that they become photoluminescent. The photoluminescence can be controlled by the etching conditions. In order to obtain silicon nanoparticles with stable photoluminescence properties and stable colloidal dispersions for further applications, it is important to passivate the silicon nanoparticle surfaces and coat them with functional groups. Well-dispersed particle dispersions with stable PL were obtained after surface functionalization. This provides an important step toward the further potential applications of silicon nanoparticles.; One key advantage of the gas phase laser pyrolysis process is the flexibility to make nanoparticles of different materials. Nickel and iron nanoparticles were produced successfully with controlled size distribution. Preliminary results show that this method is capable of producing metallic nanoparticles with interesting magnetic properties.; Kinetic Monte Carlo simulation of particle nucleation during thermal decomposition of silane can also be used to obtain useful information about the synthesis of silicon nanoparticles. In this approach, a simulation follows the evolution of a single silicon-hydrogen cluster as it reacts with its environment and grows, possibly to eventually become a particle, or disintegrates. An improved group additivity method is used to estimate the thermochemical properties of silicon-hydrogen clusters, and thermochemically-based reactivity rules are used to estimate the rate parameters for reactions of these clusters. Useful information, such as free energy profiles, cluster size distributions, effective reaction rate constants and critical particle nucleus sizes, can be extracted from the kinetic Monte Carlo simulations.