Synergistic Lewis acid-base sites of ultrathin porous Co₃O₄ nanosheets with enhanced peroxidase-like activity

Surface Lewis acid-base sites in crystal structure may influence the physicochemical properties and the catalytic performances in nanozymes. Understanding the synergistic effect mechanism of Co₃O₄ nanozymes towards substances (3, 3o, 5, 5o-tetramethylbenzidine (TMB) and hydrogen peroxide (H₂O₂)) induced by surface Lewis acid-base sites is important to enhance the efficiency for peroxidase-like reaction. Herein, ultrathin porous Co₃O₄ nanosheets with abundant Lewis acid-base sites were prepared by sodium borohydride (NaBH₄) reduction treatment, which exhibited high-efficiency peroxidase-like activity compared with original Co₃O₄ nanosheets. The Lewis acid-base sites for ultrathin porous Co₃O₄ nanosheets nanozyme were owing to the coordination unsaturation of Co ions and the formation of defect structure. Ultrathin porous Co₃O₄ nanosheets had 18.26-fold higher catalytic efficiency (1.27×10^-2 s^-1dmM^-1) than that of original Co₃O₄ (6.95×10^-4 s^-1dmM^-1) in oxidizing TMB substrate. The synergistic effect of surface acid and base sites can enhance the interfacial electron transfer process of Co₃O₄ nanosheets, which can be a favor of absorption substrates and the generation of reactive intermediates such as radicals. Furthermore, the limit of detection of hydroquinol was 0.58 μM for ultrathin porous Co₃O₄ nanosheets, 965-fold lower than original Co₃O₄ (560 μM). Besides, the linear range of ultrathin porous Co₃O₄ nanosheets was widely with the concentration of 5.0-1, 000 μM. Colorimetric detection of hydroquinol by agarose-based hydrogel membrane was provided based on excellent peroxidase-like properties. This study provided insights into designing high-performance nanozymes for peroxidase-like catalysis via a strategy of solid surface acid-base sites engineering.