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 x 10(-2) s(-1).mM(-1)) than that of original Co3O4 (6.95 x 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 mu M for ultrathin porous Co3O4 nanosheets, 965-fold lower than original Co3O4 (560 mu M). Besides, the linear range of ultrathin porous Co3O4 nanosheets was widely with the concentration of 5.0-1,000 mu M. 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.

Automated summary

This study engineered surface Lewis acid-base sites on Co3O4 nanosheets to enhance peroxidase-like activity, resulting in higher catalytic efficiency for oxidizing substrates. The synergistic effect of acid and base sites on Co3O4 nanosheets improved interfacial electron transfer, facilitating substrate adsorption and generation of reactive intermediates. The ultrathin porous Co3O4 nanosheets showed superior performance in detecting hydroquinol with a wider linear range, offering a colorimetric detection method based on agarose-based hydrogel membrane.