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, HAuCl ₄ 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 (NO _x), demonstrating its great potential in determining the intracellular concentration of NO _x. The proposed MW-assisted synthesis method is simple, fast and should be applicable to prepare various protein- or enzyme-protected metal nanoclusters.