Colorimetric detection toward halide ions by a silver nanocluster hydrogel

Abstract 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 μM and 200 μM of Cl−, 5 μM and 100 μM of Br−, 5 μM and 100 μM 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.