A green and effective anti-corrosion and anti-microbial inhibitor of citric acid-based carbon dots: Experiment and mechanism analysis

Citric acid-based carbon dots (CA-CDs) with different amounts of heteroatoms N were obtained through hydrothermal synthesis method. The microstructure, optical, antibacterial and anticorrosive behaviors were systematically analyzed. Through detection, the N atoms existed in the form of pyridine-like N, pyrrole-like N and graphitic N, and promoted the grain coarsening of carbon dots. The CA-N-CDs displayed obvious pH dependence and good stability from optical behavior analysis. The antibacterial ability of citric acid-based carbon dots was improved by inserting N atom, and the antibacterial rate was directly proportional to the amount of N atom, which was up to 95% for E. coli and S. aureus. However, the anticorrosion ability showed an initial increase followed by a decrease as the amount of N atom increased, reaching its peak at CA-N12%-CDs. At this moment, the corrosion current density (icorr) of metal was 4.68 x 10-6 A/cm2, which decreased by 122 times compared with the blank solution. Meanwhile, the corrosion inhibition rate (IE) for metal was up to 96%, which mainly depended on the tight adsorption of citric acid-based carbon dots on the metal surface.