Microwave-assisted synthesis of BSA-stabilized and HSA-protected gold nanoclusters with red emission

A microwave (MW)-assisted synthesis method for preparation of fluorescent BSA-stabilized and HSA-protected gold nanoclusters (BSA–AuNCs and HSA–AuNCs) has been developed. The reaction time can be shortened from tens of hours to several minutes, thanks to the superheating and non-thermal effects of the MW energy. The optimal experimental conditions including concentrations of BSA, HAuCl4 and NaOH and the MW programme are investigated in detail. The as-synthesised BSA–AuNC product is well characterized by UV-vis spectroscopy, fluorescence spectroscopy, HRTEM, XPS, and IR spectroscopy. The HSA–AuNCs display strong red emission which is efficiently quenched by nitrogen oxides (NOx), demonstrating its great potential in determining the intracellular concentration of NOx. The proposed MW-assisted synthesis method is simple, fast and should be applicable to prepare various protein- or enzyme-protected metal nanoclusters.