The Preparation Of Composite Silica Nanomaterials And Their Applications To Fluorescence Analysis

This dissertation consists of six chapters, including overview of applications of nanomaterials in analytical chemistry; synthesis and application of rhodamine doped silica nanoparticles; synthesis and application of fluorescein-rhodamine composite silica nanoparticles; synthesis and application of hemin doped silica nanoparticles; synthesis and application of silica nanotube array membranes; the conclusion and prospect of the present research work.In chaper one, highlights of new findings with significance in application of nanomaterials in modem analytical chemistry are viewed. The mechanisms, synthesis methods, character studies and various applications of nanomaterials in analytical chemistry are given. The research proposal for this dissertation is also presented.In chapter two, the preparation and utilization of novel fluorescent rhodamine doped silica nanoparticles are reported. This chapter is divided into two sections.In section one, a fluorophore modified silica precursor is synthesized by the reaction of amino-reactive organic fluorphores, lissamine rhodamine with 3-aminopropyltrimethoxysilane (APTMOS). Then the sol-gel method in reverse microemulsions is used to produce discrete fluorescent hybrid rhodamine-silica nanoparticles that display excellent optical properties. These nanoparticles have shown several unique advantages over existing dye molecules, quantum dots, and latex-based fluorescent particles in easy preparation, a variety of derivative methods, good biocompatibility, photostability, low toxicity, and high sensitivity. The fluorophores doped inside the nanoparticles are well protected from the surrounding environments and, thus, the potential quenching and bleaching in solution are largely decreased. The optical properties of these nanoparticles make them particularly useful as sensitive and photostable fluorescent probes for further development of immunosensors and bioanalytical applications. And a novel particulate label based on fluorescent rhodamine doped silica nanoparticles with the potential to create highly amplified fluoroimmunoassay assays is reported. The sensitivity is greatlyincreased when compared with the corresponding immunoassay performed with direct fluorophore labeling. The present work shows that these nanoparticles are high-quality markers for biochemical assays. They are not limited to dope a given fluorophore, moreover, silica shell surface can be functionalized in numerous ways to meet different needs.In section two, a fiuorimetric method using the nanoparticles is proposed for the determination of trace amount of nitrite. The method is based on the fluorescence quenching of rhodamine by the reaction product of nitrite and potassium iodide in acidic solution. The sensitivity of the method is higher than that of conventional methods. This method has been applied to the determination of trace nitrite in real samples with satisfactory results, and proved to be simple, rapid and economical.In chapter three, the synthesis and applications of novel fluorescein-rhodamine composite nanoparticles are studied. This chapter is divided into two sections.In section one, the method for the preparation of novel fluorescein-rhodamine composite nanoparticles is described. Both of the dyes, fluorescein isothiocyanate (FITC) and rhodamine, are immobilized to the composite silica nanoparticles, however, FITC, which serves as the indicative dye, is immobilized on the surface of nanoparticels, and rhodamine, which is used as the reference dye, is encapsulated in the cores of the nanoparticles. The fluorescence of FITC on the surface of nanoparticels responds sensitively to the change of environmental pH over the pH range of 5.5-7.5, but the fluorescence intensity of rhodamine is basically unchangeable to the environmental pH in this case. Therefore, a ratiometric method can be used to monitor the changes of pH, thus the precise and sensitivity of the determination can be increased. This method promises to be used to in-vivo, real-time determination of H+ in cell.In secti...