Synergism of gold and silver invites enhanced fluorescence for practical applications

Abstract

Synergism of gold and silver, causing enhanced fluorescence, has been reported in cluster science with higher photochemical stability and practical applications. The electronic factor, nuclearity, size effect etc., bring autofluorescence, doping/alloying, aggregation induced fluorescence, core–shell interaction, oxidation induced interaction and silver effect. The plausible interplaying mechanisms behind the synergism in the bimetallic clusters has been focused upon. Appropriate selection of the template is mandatory to achieving AuAg bimetallic clusters. Such templates are scarce and only a few are reported in the literature while templates to obtain individual Au and Ag clusters are numerous. Semi/complete reduced gold and non/complete reduced silver are one of the important features of such bimetallic clusters. Mingled Au and Ag has a profound effect on the stability, electronic structure and band energy of the bimetallic clusters. The arrangement of Au and Ag atoms in the bimetallic clusters is also a matter of interest. The bimetallic AuAg clusters are found to be superior to not only individual Au/Ag clusters but also carbon and semiconductor quantum dots, considering their emissive nature, toxicity, ease of synthesis, robustness etc. Water miscible as well as water immiscible solvents are equally efficient for the production of AuAg bimetallic clusters. Finally, such bimetallic clusters have proved to be unique candidates in the context of practical applications, namely sensing, catalysis, surface enhanced Raman spectroscopy (SERS), metal enhanced fluorescence (MEF), bio-imaging, synthesis of anti-bacterial cotton/papers etc. The ratio of Au and Ag not only tune the fluorescence behavior but also toxicity, as described.