Single-atom Pd catalysts as oxidase mimics with maximum atom utilization for colorimetric analysis

Pd-based nanomaterials have shown great promise as potential mimic enzymes, but conventional catalysts use only a small fraction of the Pd content that located on the catalyst’s surface. Herein, we demonstrated that maximum atom utilization could be achieved by using single-atom Pd catalysts as oxidase mimic. The single-atom Pd nanozymes exhibit significantly enhanced catalytic efficiency, with a catalytic rate constant (K_cat) and the catalytic efficiency (K_cat/K_m) values more than 625 and 4,837 times higher than those of horseradish peroxidase, respectively. A combined experimental and theoretical calculation reveals reactive oxygen species involved catalytic mechanism which endows single-atom Pd catalysts with excellent colorimetric analysis performance. Benefiting from the maximum atom utilization efficiency and well-defined structural features, the single-atom Pd nanozymes could be successfully applied for the total antioxidant capacity of fruit, determining the serum acid phosphatase activity as well as constructing NAND logic gate. This finding not only provides an effective strategy to maximize the noble-metal atom utilization efficiency as enzyme mimics, but also provides a new idea for extending their possible applications.