MnO2 nanowires tuning of photoluminescence of alloy Cu/Ag NCs and thiamine enables a ratiometric fluorescent sensing of glutathione

Abstract

By tuning the photoluminescence of alloy Cu/Ag nanoclusters (NCs) and thiamine (VB1) simultaneously through MnO2 nanowires, we report a simple and label-free ratiometric fluorescent platform for sensitively and selectively sensing of glutathione (GSH). Ag doping of Cu NCs significantly enhances the quantum yield (QY, about 2-fold enhancement), oxidation resistance to air, storage stability (60 days versus 1 day), photostability and salt stability of the resultant Cu/Ag NCs. Impressively, MnO2 nanowires quench the fluorescence of Cu/Ag NCs, while they enhance the fluorescence of nonfluorescent VB1 via oxidation reaction between VB1 and dissolved oxygen to produce oxVB1 as a nanozyme catalyst. Upon introduction of GSH as a target, the MnO2 nanowires are reduced to Mn2+ and lose their quenching capacity and oxidase-like activity, resulting in FL recovery of Cu/Ag NCs and fluorescent decrease of oxVB1. Hence, a ratiometric luminescence signal is obtained, providing a novel ratiometric fluorescent strategy for detecting GSH through target induced regulation of the catalytic activities and quenching ability of MnO2 nanowires. The sensor exhibited a wide linear concentration range (10 nM to 70 μM) for GSH with a detection limit of 6.5 nM. The ratiometric sensor was successfully used for GSH detection in biological samples.