PPy and CQDs-doped novel CuO nanocomposites for enhanced antibacterial activity against drug-resistant bacteria.**

With the development of modern medicine, the use of antibiotics is more and more extensive, drug-resistant bacteria appear, the antibacterial effect of traditional antibiotics becomes weak, and new drugs are urgently needed to solve the problem of bacterial resistance. In this paper, carbon quantum dots (CQDs) were synthesized by hydrothermal method, polypyrrole (PPy) was synthesized by chemical polymerization, and PPy/CuO/CQD ternary composite was formed by composite with copper oxide. FT-IR and XPS were used to characterize and analyze the chemical composition of PPy/CuO/CQDs. XRD results confirmed the purity of CuO, and SEM and TEM images showed that the addition of CQDs made CuO nanorods distributed evenly on PPy nanosheets. In vitro antibacterial experiments showed that PPy/CuO/CQDs nanocomposites had high antibacterial performance against Escherichia coli, Staphylococcus aureus, and methicillin-resistant Staphylococcus aureus. When the concentration of PPy/CuO/CQDs nanocomposites was 0.5 mg/mL, the growth inhibition of the three kinds of bacteria could reach 99.99 %, and the antibacterial effect was realized by the synergistic effect of the three components. It provides a good idea for the development of antibacterial drugs in medicine. In addition, in vitro cell proliferation experiments showed that PPy/CuO/CQDs complex had an anti-tumor effect on HepG2 cells.