Synthesis Of Composite Nanomaterials Andapplications In Chemical Detection Based On Single Molecule Imaging

In recent years, nanomaterials have attracted considerable attentions due to promisingapplications in biological and chemical analysis and enviromental science with the continuousdevelopment of nanotechnology. Entering the21st century, nanotechnology has been rapiddevelopment. Lots of functional nanomaterials have been successfully synthesized, theresearches of which in various fields have gone deep unceasingly, especially in chemicalsensing and biomedical imaging. Controllable preparation of nanomaterials is the basis of theuse of nanomaterials widely; and how to realize the more sensitive detection is a big problemfor chemical workers. The obtained signal at single-particle level is more accuracy than theaverage signal of the bulk detection, making the limit of single-particle detection is lower.This method has become an important tool for studying the bahavious and functions ofbiomolecules at sigle cell level. On the basis of the existing research, we have studied thesynthesis of composite nanomaterials as well as the applications in chemical sensing andbiological imaging at single particle lever. The main points of our work are summarized asfollows:In chapter2, we have applied Au-Ag core-shell plasmonic nanoparticles (PNPs) asprobes to realize the quantitative detection of hydrogen sulfide. The spectral response range ofthe51nm PNPs was specifically designed to match the most sensitive region of colorcameras. The expression for the scattering spectra of core–shell structure nanoparticles wasderived based on quasi-static theory. The principle of the color change due to the reactionbetween PNPs and hydrogen sulfide are discussed. The results obtained by UV-visiblespectroscopy as well as the calculated results suggest that the nanoprobes we designed couldbe used for the analysis and detection towards HS-specifically.In chapter3, we present a high-throughput strategy for sensitive detection of H2S byusing individual spherical Au-Ag core-shell plasmonic nanoparticles as molecular probes.This method is based on quantification of color variation of the single PNPs resulting fromformation of Ag2S on the particle surface. High density of immobilized PNPs and rapid colorRGB analysis allow a large number of individual PNPs to be monitored simultaneously,leading to reliable quantification of color change of the PNPs. A linear logarithmicdependence on sulfide concentrations from50nM to100M was demonstrated by using thiscolorimetric assay.In chapter4, we systematically investigated the synthesis of Upconversion fluorescentnanoparticles (UCNPs) and studied the fluorescent spectrum of the prepared nanoparticles.Generally, the temperature and reaction time were considered as important factors to the growth of hydrothermal products. Then the oil soluble UCNPs were transferred into aqueousphase and the water soluble UCNPs were used for the cellular imaging in our experiment.Cell images with both high signal to noise and signal to background were obtained, indicatingthat UCNPs can be used in the biolabeling and bioimaging for complex biological media suchas cells and tissues.