Near-infrared fluorescence probes for the selective and sensitive detection of sulfur ions based on glutathione capped gold nanoclusters†

The excellent anti-interference ability of near-infrared (NIR) fluorescent materials derived from long-wavelength emission has made them one of the most fascinating fluorescence probes. In this work, gold nanoclusters stabilized with glutathione (GSH-AuNCs) were prepared and exhibited excellent NIR fluorescence at 806 nm, indicating their potential as excellent fluorescence probes. It is gratifying that S²⁻ could be sensitively and rapidly recognized through the “turn-off” strategy of NIR fluorescence of AuNCs. It is speculated that the quenching was due to the aggregation-caused quenching (ACQ) phenomenon. The combination of a longer wavelength emission of 806 nm and the strong binding ability of Au and S endowed the constructed sensing system with outstanding sensitivity and selectivity. A good linear relationship for the detection of S²⁻ was obtained in the range of 0–23.75 μM, with a limit of detection (LOD) of 14.67 nM (S/N = 3). This NIR fluorescence probe was successfully used for the detection of S²⁻ in real samples with satisfactory results.