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.