Photoreductive Synthesis Of Fluorescent Metal Nanoparticles Using Multi-Functional Polymer Ligands

In the21th century, metal nanomaterials, which have special physicochemicalproperties, possess promising potential application prospect in electronics, catalysis,sensing, optics, biolabeling, molecular recognition, target drug delivery and optoelectronics.Due to their good stability, unique photoelectric effect and excellent biocompatibility, theyhave become important research area both at home and abroad. With the size decreasing,the surface energy of metal nanomaterials increases, which lead to the agglomeration of theunstable metal nanomaterials. The key to prepare stable and small size metal nanomaterialsis that choose the proper protected agent and precise control anisotropic crystal growth.Among varies method to prepare metal nanomaterials, photoreduction is a newlydeveloping and green method.Compared with other approaches, photoreduction avoids the use of additional reducingagents in addition to it being a clean, non-toxic and less time-consuming approach.Multi-functional thioether polymer ligands have enormous advantages, such as betterstability and controllability, easy modification, easy ligand exchange and low toxicity. Inthis paper, the oil-soluble and water-soluble multi-functional polymer ligands weredesigned and synthesized, prepared fluorescence metal nanoclusters (MNCs) withsmall-sized, monodisperse and unique physical properties by photoreduction, which werebetter than those prepared by traditional methods. And their properties had beencharacterized by transmission electron microscopy (TEM), fluorescence spectroscopy,X-ray photoelectron spectroscopy (XPS), Matrix auxiliary laser analytical ionizationtime-of-flight mass spectrometry (MALDI-TOF-MS), ultraviolet-visiablespectrophotometer (UV-Vis) and so on. The main contents are listed as follows:1. Water-soluble fluorescent copper, silver and gold nanoclusters which weremonodisperse and highly fluorescence, were prepared by photoreduction method withoutany reduce agents. The quantum yields were2.2%,6.8%,5.3%and the diameters were0.7±0.3nm,0.5±0.2nm,0.6±0.4nm respectively. This method avoided the influent of the properties by adding metal reducing agent, solved problems such as unstable andagglomeration. It was the first time to synthesize water-soluble fluorescent copper and goldnanoclusters by photoreduction method. We discussed some main factors which wereinfluent the fluorescent properties and diameters of metal nanocluaters such as the molarratio between the polymer ligand and different metal precusors, photoreduction time, pHvalue of solutions and metal ions. These metal nanoclusters will have potential applicationprospect in electronics, catalysis, sensing, optics, biolabeling, molecular recognition, targetdrug delivery and optoelectronics.2. A facile preparation of highly fluorescent Au NCs using oil-soluble multifunctionalpolymer ligands in one step method by photoreduction without reduce agent was reported.Major aspects including the concentration of polymer ligands and photoreduction timewere discussed. This technique made up for the shortcomings including large size andpolydispersity. In addition, Au NCs with high fluorescent quantum yield of20%will beapplied in the field of optoelectronics.