Colorimetric detection toward halide ions by a silver nanocluster hydrogel

We reported a novel colorimetric method for highly selective halide ions (Cl-, Br- and I-) recognition by Ag nanoclusters hydrogel (Ag-NCs hydrogel). The Ag-NCs hydrogel could discriminate Cl-, Br- and I- ions from a wide range of environmentally important anions, identified by the distinct UV-vis absorption band changes or the change in the color of Ag-NCs hydrogel. On the basis of this strategy, 20 mu M and 200 mu M of Cl- 5 mu m and 100 mu M of Br-, 5 mu M and 100 mu M of I- could be recognized within 5 min by UV-vis spectrum and naked eye observation, respectively. The surface color of hydrogel changed from yellow to dark green for Cl-, to brown for Br-, and to deep brown for I-. In addition, this sensing method had been applied successfully to detect chloride anion in real water samples such as tap water, pond water and pure water. Therefore, this rapid, facile, and cost-effective colorimetric assay based on Ag-NCs hydrogel was attractive and promising.