Green Synthesis And Properties Study Of Fluorescent Silver Nanoclusters

Metal nanoclusters (such as gold, sliver, and copper) consisting of severalto tens of metal atoms are new fluorescent and water-soluble molecular aggregationsdue to their ultrasmall size. They have broad application prospects in biosensors andchemical sensors, novel catalysts, biological labeling and environment monitoringattributing to their unique characteristics such as quantum size effect, goodbiocompatibility, good photostability, strong anti-aggregation ability, and large Stokesshift. However, there are still some shortcomings related to the synthesis andapplications of metal nanoclusters such as high sensitive analysis method, highchemical performance and poor stability. Therefore, we have mainly studied on thegreen synthesis of silver nanoclusters based on poly(methyl acrylic acid)(PMAA) asthe template as well as their applications in fluorescence analysis. This thesis focuseson the following two parts:First, Based on poly(methyl acrylic acid)(PMAA) as the template, we designedsuccessfully the synthesis of AgNCs with strong red fluorescence and good stabilityemploying the sunlight irradiation. The method is rapid, simple, easy to operate, andfriendly to environment. At the same time, it was found that the as-prepared AgNCs asa fluorescent probe could selectively interact with thiol-containing amino acid(cysteine) via the strong Ag-S interaction, inducing the aggregation of AgNCs into Agnanoparticles with large size, accompanied with the effective fluorescence of AgNCs.Otherwise, the common other amino acids does not quenching the silver nanoclusterseffectively because they do not contain thiol functional groups. This work achievedhighly selective detection of cysteine in a broad concentration range (1~200nmol/L)and the limit of detection is0.57nmol/L. On this principle, It established a rapid,simple, high sensitive and high selective method of detect biological thiol compounds.Meanwhile, the antibacterial properties of PMAA-templated Ag NCs were studiedagainst a Gramnegative organism, Escherichia coli. It was found that the Ag NCsinhibit the growth of these bacteria in a very strong manner, indicating the easilyobtained Ag NCs may have potential in the expanding antimicrobials market. Then, It report a novel “sign-on” fluorescent method for the determination ofMezlocillin baypen and L-ascorbic acid employing the prepared PMAA-AgNCsprobe, based on the strong fluorescence quenching effect of Hg2+on PMAA-AgNCsas well as the specific recognition between Hg2+and Mezlocillin baypen. Thisstrategy would reduce the background signal, improve the sensitivity of the detectionand achieve the highly specific recognition. The novel detection method is rapid,simple, highly sensitive, and have a good linear relationship. The study would providea distinctive research idea.for other sensitive and specific biochemical detection.