Synthesis And Antibacterial Properties Of Silver-based Nanoparticles Decorated G-C₃N₄ Composites

In view of a series of problems caused by bacterial contamination,it is an effective way to develop new antibacterial materials with high efficiency,safety,stability and lasting effect.Photocatalytic materials can produce bactericidal groups by using light conditions,and can be used in experiments to resist bacteria for a long time.This work chooses graphite carbon nitride?g-C₃N₄?with stable chemical performance,good photocatalytic properties was chosen as matrix in our work,silver based nanoparticles were decorated on g-C₃N₄ by using chitosan as surfactant,silver/chitosan/g-C₃N₄?Ag/CTS/CN?and silver-cuprous oxide/chitosan/g-C₃N₄?Ag-Cu₂O/CTS/CN?composite materials had been prepared.The influence of preparation method and microstructure on the photoelectric properties and antibacterial properties were investigated.The main research contents and conclusions are as follows:1.Ag/CTS/CN composites were successfully prepared by simple microwave method using ascorbic acid and NaBH₄ as reductants.As the surface activity of chitosan,the dispersion of the composite material was effectively improved,and Ag NPs was uniformly adhered to the surface of g-C₃N₄.The diameter of Ag NPs prepared by ascorbic acid reduction was 10-15 nm,which was smaller than that prepared by sodium borohydride reduction?10-35 nm?.2.Ag NPs in Ag/CTS/CN composites significantly improved the antibacterial performance.Under visible light conditions,the minimum inhibitory concentration?MIC?value of Escherichia coli of Ag/CTS/CN composites prepared by ascorbic acid was 40 ppm and minimum bactericidal concentration?MBC?was 30 ppm,converted to silver concentrations were 11.22 ppm and 8.42 ppm.Ag NPs can more effectively improve the photocatalytic efficiency of g-C₃N₄ and increase the production of reactive oxygen radicals?ROS?.The reactive oxygen groups generated in the photocatalytic process and Ag⁺released by silver nanoparticles act on bacteria together,thus improving the photocatalytic antibacterial effect.It is found that hydroxyl radical plays a major role in the process of reactive oxygen radical sterilization,and ascorbic acid as a reducing agent is more suitable for this system.3.In order to reduce the dependence of the composite material on Ag NPs,it was decided to introduce Cu₂O and Ag-Cu₂O/CTS/CN composite material was successfully prepared by hydrothermal method and microwave method.The diameter of Ag NPs was about 18 nm and that of Cu₂O NPs was about 5 nm.In the composites,although the cuprous oxide loading rate was lower,the amount of silver was further reduced,and the antibacterial properties of the materials were significantly improved at visible light conditions.The MIC and MBC values of Ag-Cu₂O/CTS/CN composites with 1:2 ratio of silver and copper converted to the Ag concentrations were 7.78 ppm and 3.89 ppm,respectivly.Results showed that Ag-Cu₂O/CTS/CN composites had better antibacterial propterty under visible light irradiation.