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 (CDsEDTA-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 CDsEDTA-Me nanozymes determines enzyme-mimicking activities. CDsEDTA-Fe, CDsEDTA-Cu, and CDsEDTA-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 CDsEDTA-Fe to H2O2 is improved by 47 times. The Vm value of CDsEDTA-Fe with TMB as the substrate is 1.19 × 10–7 M s–1. POD-mimicking activity of CDsEDTA-Me nanozymes increases linearly with the increase of stability constants of CDsEDTA-Me, which indicates that the POD-mimicking activity of CDsEDTA-Me can be predicted by stability constants of CDsEDTA-Me. CDsEDTA-Me provides a coordination chemistry strategy for the construction of CDs-metal nanozymes and rational improvement of enzyme-mimicking activities.