To Love and to Kill: Accurate and Selective Colorimetry for Both Chloride and Mercury Ions Regulated by Electro-Synthesized Oxidase-like SnTe Nanobelts

Herein, SnTe nanobelts (NBs) with efficient oxidase–mimetic activity were synthesized by the simple electrochemical exfoliation method. A specific inhibition effect of Cl– on the enzymatic behavior of the pure SnTe NBs was discovered, which was accordingly used for establishing a highly feasible, sensitive, selective, and stable Cl– colorimetric assay. The detection concentration range was 50 nM to 1 mM, and the lowest detection limit was 20 nM for Cl–. In addition, a signal on-off-on route based on the SnTe NB nanozyme was designed to realize the reliable and specific detection of Hg2+. Therein, the SnTe NBs were grafted with gold nanoparticles to form a hybrid of SnTe/Au, resulting in the depression of the oxidase-like activity, which can then be recovered in the presence of the Hg2+ due to the formation of a gold amalgam. Especially, it was found that the high concentration of Cl– over 3 mM could again exert suppression influence toward the enzymatic activity of the SnTe/Au–Hg system. Based on the to-love-and-to-kill interaction between Cl– and Hg2+, the detection range for Cl– can be extended to 40 to 250 mM. In return, the assays of Cl– could avoid in advance its interference toward the accurate Hg2+ assays. We systematically clarified the oxidase-like catalytic mechanism of the SnTe-derived nanozyme systems. The as-proposed colorimetry can be successfully applied in practical samples including the sweat, human serum, or seawater/tap water, relating to cystic fibrosis, hyper-/hypochloremia, or environmental control, respectively.