Cerium-mediated photooxidation for tuning pH-dependent oxidase-like activity

Industrial and medical applications of most nanozymes are often limited by their pH-dependent activities as well as by weak response to external stimuli. Here we report a light-controlled nanozyme possessing tunable oxidase-like activities without incurring the burden of pH effects. This nanozyme comprises carbon dots (CDs) and Ce3+ ions and its activities can be regulated with rational design of their concentration ratio. Unlike previously reported nanozymes, yet it can perform optimally at neutral pH values for catalytic oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB). We find that its unique attribute originates from pH-dependent ability of CDs to reversibly switch from Ce3+ to Ce4+ under visible light irradiation. Therefore, our presented nanozyme can be applied in real environment and be simultaneously remotely-controlled by visible light.