Microwave-assisted one-pot synthesis of anisotropic gold nanoparticles with active high-energy facets for enhanced catalytic and metal enhanced fluorescence activities

A simple sustainable method has been reported for the synthesis of highly active Au nanoparticles (NPs) having sharp edges and corners using oxalic acid as a reducing agent. Different chloroauric acid to oxalic acid mixing ratios were studied and it was found that the 1 : 3 ratio gives better structures with high energy {110} facets, which are highly efficient for catalysis and metal enhanced fluorescence (MEF) activities because of the presence of many edges and corners. The reaction rate was also found to be fast at 50 degrees C compared to that under the ambient conditions. In the case of microwave (MW) heating, the control of the size and shape of Au NPs was better than that in hotplate heating. The MEF of rose bengal (RB) dye was found to be 5.0 times better for Au NPs synthesized at a 1 : 3 mixing ratio and under MW heating compared to spherical NPs. The same NPs were also found to have very good efficiency in metal enhanced singlet oxygen generation and catalytic reduction of 4-nitrophenol to 4-aminophenol.