Recyclable fluorescent gold nanocluster membrane for visual sensing of copper(ii) ion in aqueous solutionElectronic supplementary information (ESI) available: Fig. S1-S5. See DOI: 10.1039/c2an35068h

Recently, metal-selective fluorescent chemosensors have attracted intense attention for their simple and real-time tracking of metal ions in environmental samples. However, most of the existing fluorescent sensors are one-off sensors and thus suffer from large amount of reagent consumption, significant experimental cost and raising the risk of environmental pollution. In this paper, we developed a green (low reagent consumption, low-toxicity reagent use), recyclable, and visual sensor for Cu 2+ in aqueous solution by using a fluorescent gold nanoclusters membrane (FGM) as the sensing unit, basing on our findings on gold nanoclusters (Au NCs) that the bovine serum albumin (BSA)-coated Au NCs exhibit excellent membrane-forming ability under the isoelectric point of BSA, and thus enable us to obtain a new type of sensing membrane ( i.e. FGM) by denaturing Au NCs; the fluorescence of FGM can be significantly quenched by Cu 2+ ion, and the quenched fluorescence can be totally recovered by histidine; the as-prepared FGM is very stable and recyclable, which makes it an ideal sensing material. A green and recyclable fluorescent gold nanocluster membrane (FGM)-based sensor has been developed for sensing Cu 2+ ion due to the selective and reversible quenching of FGM fluorescence by Cu 2+ ion.