A highly selective sensor of cysteine with tunable sensitivity and detection window based on dual-emission Ag nanoclusters

An effective dual-emission fluorescent Ag nanoclusters (NCs)-based probe have been constructed for rapid and selective detection of cysteine (Cys) with tunable sensitivity. Electrostatically induced reversible phase transfer method is employed to synthesize Ag nanoclusters with tunable emission intensity at 430   nm and 630   nm by controlling molar ratio between Ag and glutathione . The fluorescence of the Ag nanoclusters could be selectively quenched in the presence of Cys with a detection limit as low as 10   nM. Good linear correlations are obtained over the concentration range from 0.5 to 55   μM (quenched emission at 630   nm), 55 to 120   μM and 120 to 220   μM (enhanced emission at 555   nm) and 120 to 200   μM (quenched emission at 430   nm), respectively. The long-wavelength emission of the Ag nanoclusters can avoid the interference of the autofluorescence of the biosystems , which facilitated their applications in monitoring Cys in urine.