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 (3,3′,5,5′-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−1·mM−1) than that of original Co3O4 (6.95 × 10−4 s−1·mM−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.