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

Abstract

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.