Optical Characterization of Ultrasmall, Hydrogen-Terminated and Carboxyl-Functionalized Silicon Nanoparticles in Aqueous Environments

The primary theme of this dissertation is to characterize the optical and chemical properties of ultrasmall (~1 nm) silicon nanoparticles (Si-np) in aqueous environments, focusing on their potential for use as luminescent markers in biophysical and biological applications. Two systems are presented in detail: (1) Chapters 2-4 cover hydrogen-terminated Si-np that are prepared through electrochemical dispersion of a crystalline Si wafer and (2) Chapters 5-6 discuss carboxyl-functionalized Si-np prepared via thermal hydrosilylation of surface Si-H bonds with an ω-ester 1-alkene. Figure 1.1 shows a sketch (based on our results) of an ultrasmall Si-np that is ~1 nm in diameter and contains approximately thirty silicon atoms. The chemical groups shown on the surface are the different types of species that are discussed in this work: (a) hydrogen-terminated Si-np, (b) carboxyl-functionalized Si-np, and (c) various oxidized structures. Chemical and physical characterizations are done using nuclear magnetic resonance (1H-NMR), size exclusion chromatography (SEC), and infrared spectroscopy (FTIR). Optical characterization is done via absorption and steady-state photoluminescence (PL) and using capillary electrophoresis (CE) coupled with laser-induced fluorescence (LIF) detection. The instrumentation and experimental procedures are summarized in Chapter 8.U of I OnlyPost 1923. No authorization form