Dually emitting gold-silver nanoclusters as viable ratiometric fluorescent probes for cysteine and arginine

Glutathione coated gold and silver nanoclusters (GSH-Au/AgNCs) were synthesized by one-pot reduction methods and are found to be viable fluorescent nanoprobes for cysteine (Cys) and arginine (Arg), with good selectivity over other amino acids. The GSH-Au/AgNCs have two emissions at 616 nm and 412 nm when excited at 360 nm. With the increased concentration of Cys, the ratio of the emission intensities (I-616/I-412) linearly decreases with Cys in concentration ranging from 0.05 to 10 mu M and from 10 to 50 mu M, respectively. With increased concentrations of Arg, the ratio of I-616/I-412 linearly decreases with Arg concentration ranging from 0 to 50 mu M and from 50 to 100 mu M, respectively. The probe was applied to the determination of Cys and Arg in spiked samples of serum and urine where it gave good recoveries.