Facile, rapid one-pot synthesis of multifunctional gold nanoclusters for cell imaging, hydrogen sulfide detection and pH sensing

In this study, we have developed a facile, rapid one-pot strategy for synthesis of orange fluorescent gold nanoclusters (MBISA-AuNCs) at room temperature by using 2-Mercapto-5-benzimidazolesulfonic acid (MBISA) as both reducing and protecting reagent. The prepared AuNCs exhibited prominent advantages including high fluorescent quantum yield, good water solubility, excellent biocompatibility and low toxicity. Based on these superior properties, the AuNCs have been multi-talented applied in cell imaging, hydrogen sulfide detection and pH sensing. Confocal fluorescence imaging showed that the MBISA-AuNCs could enter living cells and distribute in the cytoplasm. Additionally, the obtained AuNCs could visualize H2S fluctuations in living cells without interference of autofluorescence based on their high sensitivity and selectivity detection for H2S with a linear range of 2.7 x 10(-11)-8.5 x 10(-4) M and a detection limit of 0.024 nM. Most strikingly, the AuNCs exhibited strong pH dependent behavior and responded linearly, rapidly and reversibly to minor pH fluctuations within the range of 2.01-12.00. Therefore, the AuNCs could also image pH fluctuations in live cells with negligible autofluorescence and provided a new method of analysis to visualize monitoring wide pH range change in live cells.