Generation of Enzymatic Hydrogen Peroxide to Accelerate the Etching of Silver Nanocrystals with Selectivity

We report a simple and versatile system for generating highly concentrated H₂O₂ on the surface of nanoparticles through enzymatic oxidation of glucose. It involves immobilization of glucose oxidase, a negatively charged enzyme, on the surface of a positively charged metal nanoparticle via electrostatic attraction. Upon the introduction of glucose at a concentration of 1.7 mM, this system is able to produce enzymatic H₂O₂ on the surface of the nanoparticle, with oxidation power equivalent to that of aqueous H₂O₂ at a concentration of 5 M when it is directly added into the reaction solution. We have evaluated the system for the etching of both twinned and single-crystal Ag nanocubes. We identified that the highly localized and concentrated H₂O₂ generated on the surfaces of Ag twinned cubes would lead to selective etching from the {111} facets parallel to the twin plane, in a fashion identical to the growth process but in the reversed order. For Ag single-crystals nanocubes, the etching would initiate from the corners to gradually transform the cubes into spheres. This study offers the opportunity to control the etching of metal nanocrystals with selectivity for elucidating the mechanism and diversifying the nanocrystals.