Preparation of graphene quantum dots/Ce-2-methylimidazole heterojunction and its wide-spectrum antibacterial activity

As a new antibacterial method, photocatalysis has attracted extensive attention. The development of high-efficiency visible light catalyst is one of the hot research directions. In this work, graphene quantum dots (GQDs) were synthesized by a green-chemical method. GQDs/Ce-2MI was obtained via one-pot precipitation method at room temperature using GQDs, cerium nitrate and 2-methylimidazole (2MI) as raw materials. Different ratios of GQDs/Ce-2MI samples were obtained by controlling the initial amount of GQDs solution. Through photoelectrochemical test, it is found that 25vol%GQDs/Ce-2MI displayed high photocurrent response performance. Furthermore, using 2MI as fixed organic ligand, M-2MI with different central metal ions (Mⁿ⁺: Co²⁺, Fe²⁺, Fe³⁺) were synthesized and compared. Under visible light irradiation, the antibacterial properties of different catalysts were investigated using Escherichia coli (E. coli) as target strain. The results indicate that GQDs/Ce-2MI displays the optimal antibacterial performance. After 60 min of visible light irradiation, more than 99% sterilization effect can be achieved. Using the optimized GQDs/Ce-2MI as photocatalyst, the effects of light source wavelength and different bacterial species were studied. The results indicate that GQDs/Ce-2MI has good antibacterial ability in a wide spectrum range and universal antibacterial effect toward Staphylococcus aureus (S. aureus). Through the quencher experiments, it can be speculated that the main active species for the inactivation of E. coli are holes (h⁺) and hydroxyl radicals (•OH).