Biomimetic Mineralization Of Gold And Silver Nanoclusters And Their Preliminary Fluorescence Detection Applications

Noble metal nanoclusters (NCs) with unique chemical and physical properties have been widely used in the fields of biological analysis, medical imagine, and catalysis. In this thesis, glutathione (GSH) and bovine serum albumin (BSA) were employed separately as templates for the synthesis of silver nanoclusters (AgNCs) and bimetallic alloying gold-silver nanoclusters(Au-AgNCs) by the biomineralization route. Three sensing systems were thereby developed for detecting phytic acid, melamine, and tyrosinase activity.1. Silver nanoclusters (AgNCs) were synthesized with powerful blue fluorescence by the biomineralization route by employing GSH as templates under ultrasound conditions. A "Turn-on" fluorimetric protocol has thus been proposed by using AgNCs as fluorescent nanoprobes for the analysis of phytic acid in ceral (Chapter 2). This protocol is proposed based on the findings that iron ions could quench the fluorescence of AgNCs, which could be turned on in the presence of phytic acid that could bind with iron ions.Compared with the traditional analysis methods, the developed fluorimetric protocol may possess some advantages of easy operation, high selectivity,and favourable sensitivity. Therefore, the developed fluorimetric protocol can promise the wide applications for the detection of phytic acid for the nutritional evaluation of ceral and the freshness of fluits.2. Bimetallic alloying gold-silver nanoclusters (Au-AgNCs) have been synthesized with powerful red fluorescence by a one-pot biomineralization route using BSA as templates. A fluorimetric protocol has been proposed using Au-AgNCs as fluorescent nanoprobes for the analysis of melamine in dairy products (Chapter 3). This protocol is proposed based on the findings that mercury ions could quench the fluorescence of Au-AgNCs. However, the presence of melamine could bind with mercury ions resulting in the turn-on fluorescence of Au-AgNCs. Compared with AuNCs and AgNCs alone,Au-AgNCs could not only have strong fluorescence, but also sensitively response to the recovery and quenching of the fluorescence. Therefore, the developed fluorimetric protocol is sensitive, selective and time-saving, which may promise the wide applications for the detection of melamine in dairy products.3. A sensitive and selective fluorimetric protocol has been proposed using Au-AgNCs as fluorescent nanoprobes for the analysis of TYR activity(Chapter 4). The fluorimetric protocol for detecting TYR activity was developed basd on the fact that dopamine could be specifically oxidized by TYR in the presence of molecular oxygen to yield dopaquinone that could quench the fluorescence of Au-AgNCs. This developed fluorimetric method shows some advantages over the traditional analysis methods in terms of detection sensitivity and selectivity, thus providing a new analysis tool for TYR activity for the diagnosis of vitiligo, albinism, and other diseases.