Iron Doped CuSn(OH)₆ Microspheres as a Peroxidase-Mimicking Artificial Enzyme for H₂O₂ Colorimetric Detection

We designed and synthesized iron doped CuSn­(OH)6 (Fe/CuSn­(OH)6) microspheres, which was selected as a nanoenzyme to detect hydrogen peroxide (H2O2), by a coprecipitation method for the first time. Significantly, Fe/CuSn­(OH)6 microspheres revealed the high peroxidase-like activity, which was evaluated using the peroxidase substrate 3,3′,5,5′-tetramethylbenzidine (TMB) catalytically oxidized by H2O2. Colorless TMB could be turned into oxidized TMB (oxTMB) with a blue color change in the process of oxidation. The catalytic reaction mechanism has been proved to be •OH, attributing to H2O2 decomposition. On the basis of the high peroxidase mimetic activity of Fe/CuSn­(OH)6 microspheres, a novel, simple, and sensitive H2O2 colorimetric detection system was successfully constructed. Experimental data revealed that the Fe/CuSn­(OH)6 microspheres nanoenzyme additionally demonstrated the high peroxidase-like activity compared with horseradish peroxidase. Furthermore, based on the Fe/CuSn­(OH)6, a rapid detection of H2O2 could be come true in the wide range (30–1000 μM) with a lower detection limit of 9.49 μM (S/N = 3). The feasibility of this convenient method was confirmed by qualitative detection of H2O2 residue in milk