Synthesis And Properties Of Fluorescent Ag Nanocluster

As a new type of luminescent nanomaterials, metal nanoclusters (NCLs), whichcontain from of a few to roughly a hundred of metal atoms, recently have attracted agreat deal of interest. In particular, Ag NCLs show more excellent fluorescenceproperties than other noble metal NCLs in solution and have received considerableattention due to the potentials, such as biological labeling, immunoassays, opticalsensing. However, Ag NCLs is very difficult to be synthesized in the aqueous solutionbecause of the aggregation and also exhibie poor stability. Hence, there is an enduringchallenge to prepare novel, stable and water–soluble Ag NCLs with intenseluminescent propenties.In this study, two parts of work had been completed: Firstly, the water soluble andfluorescent Ag NCLs were successfully prepared at room temperature with usingglutathione as stabilizing reagent and hydrazine hydrate as reducing reagent. Thechemical structure and properties of resultant Ag NCLs were characterized byultraviolet/visible (UV/Vis) spectroscopic, photoluminescence spectroscopic, X–raypHotoelectron spectroscopy (XPS), X–ray diffraction (XRD), transmission electronmicroscope (TEM) and FT–IR spectrum. The as-prepared Ag NCLs showed redemission line with full width at half maximum about~90nm and narrow sizedistribution with average size of~2.0nm. The time–dependent UV–Vis absorptionand fluorescent spectroscopic were investigated to confirm the formation progress ofNCLs. The as-prepard Ag NCLs were protected by glutathione and exhibitedchemical stability, which possessed many potential applications in various fields suchas biological labeling, immunoassays, optical sensing, and so on. In this study, AgNCLs were used as fluorescent probe for selective detection of Hg2+ions. Secondly,the water soluble and fluorescent Ag NCLs-SiO2microspheres were successfullyprepared and were characterized by ultraviolet/visible (UV/Vis) spectroscopic,photoluminescence spectroscopic, X–ray pHotoelectron spectroscopy (XPS), X–raydiffraction (XRD), transmission electron microscope (TEM). This resultantmicrospheres exhibited fluorescent properties with a emission peak at595nm under395nm excitation. And Ag NCLs could maintain the photo luminescent propertiesafter the Ag NCLs-SiO2microspheres were calcination at high temperature (700℃).More importantly, the full width at half maximum of the fluorescent peak was only10 nm which was much less than those reported previously. The resultant microsphereswere possessed many potential applications, owing to their excellent fluorescence andbiocompatibility, such as optical sensing, biological labeling. Furthermore, weillustrated the formation process of the fluorescent microspheres and proposed anon-ligand mechanism about the formation of fluorescent Ag NCLs-SiO2microspheres, which was significant for preparing similar fluorescent particles.