Polyhedral MnSe microparticles with specific Hg2+-suppressed oxidase-like activity: Toward a green and low-cost turn-off method for Hg2+ detection

With the attractive advantage of catalytic signal amplification, noble metal-based peroxidase-mimicking nanomaterials have been intensively used to establish optical methods for hypertoxic Hg2+ detection. However, in these methods the requirement of high-concentration H2O2 can lead to secondary pollution, and the noble metals used result in these assays’ high cost. Therefore, exploring new categories of enzyme mimics to develop environmentally friendly and low-cost approaches for Hg2+ sensing is highly desired. Herein we proposed a novel noble metal-free material, MnSe microparticles, featuring specific Hg2+-suppressed oxidase-like catalytic activity, to fabricate a green, cheap, and high-performance turn-off approach for Hg2+ detection. The MnSe microparticles with a polyhedral structure were obtained via a one-pot solvothermal process, showing excellent oxidase-like activity to catalyze the oxidation of colorless 3,3′,5,5′-tetramethylbenzidine (TMB) to its blue product. The introduction of Hg2+ can significantly mask their active sites via forming an inert layer of HgSe outside the MnSe microparticles, thus suppressing the TMB catalytic color reaction. Based on the turn-off principle, colorimetric quantification of Hg2+ was realized with high sensitivity and specificity. By integrating smartphone sensing with 3D-printed accessories and paper strips, a portable platform for the convenient detection of Hg2+ was further established, demonstrating its great practicability in real analysis.