Highly exposed Cu active sites as efficient peroxidase mimics for colorimetric analysis

Nanozymes are nanomaterials with intrinsic enzyme-mimic activity, but their large-scale application is generally limited by their low catalytic activity. Herein, we demonstrated that highly exposed Cu active sites on two-dimensional (2D) nitrogen-doped carbon (Cux/NC) can serve as efficient peroxidase-like (POD) catalysts with high atomic utilization. Specially, the uniformly distributed Cu active sites could react with H2O2 to produce singlet oxygen (1O2) under acidic conditions, which can efficiently oxidizes colorless 3,3′, 5,5′-tetramethylbenzidine (TMB) to blue oxidized TMB (oxTMB). Among various Cux/NC nanozymes studied, the Cu0.14/NC exhibited smaller maximum catalytic velocities (Vmax) and Menten constant (Km) for TMB and H2O2. Benefiting from the highly active peroxidase-like activity, the Cu0.14/NC nanozyme could be successfully applied for the hydroquinone (HQ) and ascorbic acid (AA) detection applications through the inhibitory effect of HQ and AA. More interestingly, α-glucosidase (α-Glu) detection sensing platform could be constructed based on HQ as a signal transmitter, with the detection range ranging from 0 to 12 U/L and the minimum detection limit being 0.68 U/L. This work provides not only an idea for the rational design of highly exposed Cu active sites but also fabricate an effective detection sensing platform for HQ, AA, and α-Glu detection.