Mercury(II)-stimulated oxidase mimetic activity of silver nanoparticles as a sensitive and selective mercury(II) sensor

Research on oxidase mimics is challenging but important. In this article, mercury(II) ion enabled citrate-capped silver nanoparticles (Cit-AgNPs) exhibit catalytic activity toward the oxidation of typical chromogenic substrate 3,3',5,5'-tetramethylbenzidine (TMB) by dissolved oxygen under mild conditions, suggesting a new type of oxidase mimic. In addition, the oxidase-like activity of Cit-AgNPs was sensitive to the concentration of mercury(II) ions and selective towards mercury(II) ions among other metal ions. Based on this, a facile colorimetric mercury(II) ion sensor was developed. Hg2+ was reduced on the surface of Cit-AgNPs to form Hg-Ag alloys. The Hg-Ag alloys activated oxygen and generated superoxide anions, which oxidized TMB. This discovery indicates the potential of nanoparticles for efficient enzyme mimetics.