Colorimetric chemosensors designed to provide high sensitivity for Hg2+ in aqueous solutions

The specific colorimetric detection of Hg2+ in the context of interference from coexisting metal ions in aqueous solutions is a challenge. Therefore, a series of easy-to-make Hg2+ colorimetric chemosensors S1∼S3, bearing thiourea moiety as binding site and nitrophenyl moiety as signal group, were designed and synthesized. Among these sensors, S3 showed excellent colorimetric specific selectivity and high sensitivity for Hg2+ in DMSO and DMSO/H2O binary solutions. When Hg2+ was added to the solution of S3, a dramatic color change from brown to colorless was observed, while the cations Ca2+, Mg2+, Cd2+, Fe3+, Co2+, Ni2+, Cu2+, Zn2+, Pb2+, Ag+ and Cr3+ did not interfere with the recognition process for Hg2+. The detection limits were 5.0 × 10−6 and 1.0 × 10−7 M of Hg2+ using the visual color changes and UV–vis changes respectively.

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► An easy-to-make Hg2+ colorimetric senor S3 was designed and synthesized.
► S3 showed colorimetric specific selectivity for Hg2+ in aqueous solutions.
► The detection limit is 1.0 × 10−7 M for Hg2+, pointing to the high sensitivity.