Solid‐state Synthesis of Cu doped CDs with Peroxidase‐mimicking Activity at Neutral pH and Sensing of Antioxidants

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Abstract
Carbon dots with peroxidase‐mimicking properties have attracted considerable attention for various sensing and biomedical applications. However, most peroxidase nanozymes do not show activity at neutral pH and only work in acidic conditions. In this work, crystalline Cu‐doped, Mn‐doped, and undoped carbon dots (CDs) are prepared via one‐step, solid‐state, microwave synthesis. Among them, Cu‐CDs demonstrate catalytic oxidation of 3,3′,5,5′‐tetramethylbenzidine (TMB) and 2,2′‐azino‐bis (3‐ethylbenzthiazoline‐6‐sulfonic acid) diammonium salt (ABTS) with H2O2 at pH 7 and pH 6 respectively. Our study shows that Mn‐doped and undoped CDs do not feature peroxidase‐like properties at pH=7. The mechanism and kinetics of the peroxidase‐mimicking reaction of Cu‐CDs were investigated by spectroscopic studies. Moreover, colorimetric sensing of different antioxidants was monitored based on the reduction of oxidized TMB, with selective detection of ascorbic acid in the range of ∼2–1000 μM with a limit of detection of 23.3 μM. This work introduces a facile strategy for synthesizing metal‐doped CDs with promising applications in biosensing and catalysis.

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