Rapid and Sensitive Glutathione Detection Using Water-Soluble Fluorescent Bimetallic Nanoparticles

This work aims to design and develop a simple but effective strategy for the selective and sensitive detection of glutathione (GSH) in aqueous medium by exploiting fluorescent bimetallic nanoparticles. To achieve this, water-soluble, fluorescent silver-capped gold nanoparticles (F-AgAu) has been synthesized and characterized through conventional methods. The sensing behaviour of the F-AgAu for several analytes of interest has been investigated by employing steady state and time-resolved spectroscopic techniques. Signaling strategy has been conceptualized by exploiting both "turn-on" and "turn-off" condition of the fluorescent nanoparticles against specific analytes in sequential manner. The method is based on the F-AgAu/Hg2+ system, where the initial fluorescence from F-AgAu is quenched ("turn-off") by Hg2+. Time-resolved fluorescence studies have revealed that a photoinduced electron transfer (PET) process from nanoparticle to Hg2+ is primarily responsible for the fluorescence quenching behavior. Interestingly, in the presence of GSH, the fluorescence of the nanoparticle is found to be recovered ("on" state). The fluorescence "on" state of the nanoparticles is attributed to the competitive affinity of Hg2+ for thesurface ligand, GSH. More interestingly, it has been demonstrated that the present signaling strategy is quite effective in detecting GSH in various fruits and food samples at low concentration levels.