EDTA-Functionalized Carbon Dots-Metal Nanozymes Based on Coordination Chemistry: Species of Metal Ions Determines Enzyme-Mimicking Catalyzed Activities

Metal ion-carbon based nanomaterials served as nanozymes to mimic the biocatalytic performance of natural enzymes. However, there are still challenges in constructing carbon dots (CDs)-metal nanozymes with the same coordination structure based on coordination chemistry and revealing the effect of metal ion species on enzyme-mimicking catalyzed activities. Herein, EDTA-functionalized carbon dots-metal (CDs_EDTA-Me) nanozymes with different metal ions (Fe³⁺, Cu²⁺, and Co²⁺) and the same coordination structures are synthesized based on coordination chemistry. Species of metal ions of CDs_EDTA-Me nanozymes determines enzyme-mimicking activities. CDs_EDTA-Fe, CDs_EDTA-Cu, and CDs_EDTA-Co display significant peroxidase (POD)-mimicking, superoxide dismutase (SOD)-mimicking activities, and hydroxyl radical (•OH) scavenging ability, respectively. Compared with horseradish peroxidase, the affinity of CDs_EDTA-Fe to H₂O₂ is improved by 47 times. The V_m value of CDs_EDTA-Fe with TMB as the substrate is 1.19 × 10^-7 M s^-1. POD-mimicking activity of CDs_EDTA-Me nanozymes increases linearly with the increase of stability constants of CDs_EDTA-Me, which indicates that the POD-mimicking activity of CDs_EDTA-Me can be predicted by stability constants of CDs_EDTA-Me. CDs_EDTA-Me provides a coordination chemistry strategy for the construction of CDs-metal nanozymes and rational improvement of enzyme-mimicking activities.