Cu2O nanocubes–grafted highly dense Au nanoparticles with modulated electronic structures for improving peroxidase catalytic performances

Based on the intermediate states of metal ions in metal oxide nanomaterials (NMs) that acted as the primary active species, the design of high-performance nanozymes has greatly stimulated current research in diverse biomedical applications. Herein, Cu 2 O nanocubes-grafted highly dense Au nanoparticles (NPs) was developed as an appealing nanozyme for H 2 O 2 colorimetric sensor and antioxidant detections. The obtained Au/Cu 2 O heterostructures show efficient electron-transfer from metallic NPs to Cu 2 O nanocubes owing to the difference of Fermi energy between two components. The modulated electronic structure of Au/Cu 2 O hybrids enables them to possess enhanced peroxidase catalytic activity for the oxidation of 3, 3′, 5, 5′-tetramethylbenzidine (TMB) in the presence of H 2 O 2 , which is about 32% higher than that of pristine Cu 2 O nanocubes. Then, an excellent H 2 O 2 colorimetric sensor was established by using Au/Cu 2 O heterostructures with a low limit of detection (LOD) of 0.054 μM, which is much lower than the H 2 O 2 allowance level of US FDA regulations (ca.15 μM, 0.05 wt%). The obtained Au/Cu 2 O nanoproducts exhibit pronounced long-time stability with 95% peroxidase activity maintained after keeping them for 30 days, while residual 64.5% via Cu 2 O nanocubes. Furthermore, we assessed the anti-oxidative behavior of three natural antioxidants (tannic acid, gallic acid , tartaric acid) with the LODs as low as 0.039, 0.16 and 1.55 μM, respectively, and the antioxidant capacity in the following order: tannic acid  > gallic acid >  tartaric acid . Therefore, it is believed that the as-prepared Au/Cu 2 O nanozymes have promising potential applications in fields of biomedicine and food safety.