| This dissertation research is mainly focused on the synthesis of discrete capped-silicon nanoparticles and the study of the stability of water soluble particles in acidic media. Mainly four different types of silicon nanoparticles, blue, green, and red emitting, as well as nonemitting particles, were synthesized using three different synthetic routes and the silicon particles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), infrared spectroscopy, scanning electron microscopy (SEM), photoluminescence, nuclear magnetic resonance spectroscopy, and UV-visible spectroscopy.;The silicon nanoparticles synthesized from the micro-emulsion method at room temperature are amorphous according to the XRD pattern and TEM studies. Thus in-situ heating studies of two types of silicon particles, 3-aminopropyl-capped and heptyl-capped silicon nanoparticles, were carried out in order to observe crystallization of amorphous silicon nanoparticles. The crystallization temperature for both types was around 200°C. The study was further extended to explore the size dependent melting of silicon nanoparticles.;The stability of two types of water soluble nanoparticles, 3-aminopropyl-capped and 5-aminopentanoxide-capped silicon nanoparticles, in different acidic solutions has been reported. 3-Aminopropyl-capped silicon nanoparticles show constant photoluminescence intensity, whereas 5-aminopentanoxide-capped particles show a decrease of intensity with time, suggesting that the Si-C bond is more stable than Si-O-C bond.;Silicon formate and silicon tetraacetate were used as starting materials for synthesizing silicon nanoparticles in the micro-emulsion method. The nanoparticles have a diameter around 8-10 nm and no emission was observed under UV light illumination, suggesting that the band gap energy of the silicon particles lies in the infrared region. By heating silicon tetraacetate at high temperature, crystalline silicon nanoparticles have been synthesized and the average particle size was 2.3 nm and green under UV light.;Hexachloroplatinic acid assisted etching of silicon wafer provided pure silicon nanoparticles terminated with hydrogen atoms. The nanoparticles were also capped with allylamine. The size of the silicon nanoparticles calculated by the Scherrer equation from the XRD pattern is 3.1 nm and the size is consistent with the size observed from TEM. Treatment of hexachloroplatinic acid with silicon powder always resulted in a mixture of Si and Pt nanoparticles. |
