Application Of Gold Nanoparticles In Chenmical And Biological Sensing Based On Single Molecule Imaging

Recently, due to the unique optical properties, the gold nanomaterial has attracted more and more interests of researchers and been widely applied in the chemical and biochemical sensing. Compared with other conventional optical probes, gold nanoparticles poss many advantages including easy to prepare and modify, large optical cross-section, high photostability, low biotoxicity and unique size-dependent property, which propose a promising prospect in the applications of chemical and biological sensing, In this paper, based on the optical properties of gold nanoparticles, colorimetric assay, polarization darkfield microscopy and single-particle spectroscopy were utilized to hydrogen sulfide sensing with gold nanoparticle as sensor.In chapter 2, we reported a colorimetric analysis for sulfide sensing based on a plasmonic coupling induced aggregation system using glutathione modified gold nanoparticle (GSH@AuNP) as probe. It is a sensing of sulfide which would replace the glutathione on the Au NPs through a special anion-for-molecule ligand exchange and induce the AuNPs aggregation. We achieved a quick and convenient quantitative detection of sulfide based on the change of absorption spectral shifts and intensity ratio which induced by the aggregation of AuNPs.In chapter 3, bases on unique depolarization effect of anisotropic particles with the heterogeneity in content with respect to the refractive index in comparison with isotropic particles, we developed a novel scattering switch-on detection strategy for target-induced plasmon-coupling based sensing in homogenous solution with a flash-lamp polarization darkfield microscopy, which allows selective imaging and counting of anisotropic nanoaggregates with enhanced precision and free background interferences. With hydrogen sulfide detection as a proof of concept demonstration. we achieved a sub-nM sensitivity over a dynamic range of five orders of magnitude.In chapter 4, we achieved sensitive detection of sulfide by using single-particle spectral microscopy with gold-silver core-shell nanorods as probes, whose LSPR spectrum shifts to longer wavelengths when the Ag shell react with sulfide. By using the time-dependent spectral shifting curves in various concentration obtained by previous work as external calibration curves, the concentration of H2S in live cells will be determined by detecting the LSPR spectral of single nanoprobe in real time.