Study On Preparation And Performance Of Antibacterial Materials Based On Carbon Quantum Dots/Silver Sulfide

The emergence of bacterial resistance to traditional antibiotics and its global spread has brought huge threats to human life and health,and the need for new alternative antibacterial agents has become increasingly urgent.The rapid development of nanoscience provides a potential alternative to antibacterial therapy.Compared with traditional antibiotics,nanomaterials are not easy to cause bacterial resistance due to their stronger membrane permeability and the potential for multiple antibacterial effects.However,the antibacterial performance of a single nanomaterial is not ideal.For example,metal-based nanomaterials have good antibacterial properties,but their use is restricted due to cytotoxicity;carbon-based nanomaterials have good biocompatibility,but their antibacterial properties are not.ideal.Combining different nanomaterials to prepare nanocomposite materials with excellent antibacterial properties and low cytotoxicity is the key to solving this problem.In this paper,based on carbon quantum dots(CQDs)and silver sulfide(Ag₂S),CQDs/Ag₂S/CS composite antibacterial materials,CS/Ag₂S/CQDs antibacterial hydrogels and g-C₃N₄/CQDs/Ag₂S photocatalytic antibacterial materials were prepared,and Their antibacterial properties were tested.The main research contents and results are as follows:(1)Using acetone as the carbon source,an aldol condensation reaction occurs under alkaline conditions to synthesize carbon quantum dots from the bottom up.The composition and microscopic morphology of carbon quantum dots were analyzed by FTIR,AFM,TEM,XRD,etc.Silver sulfide nanoparticles were prepared with sodium sulfide and silver nitrate,and finally CQDs/Ag₂S/CS composite materials were prepared by in-situ growth method on chitosan(CS)substrate by compounding silver sulfide and carbon quantum dots.The composition and microstructure of the composite material were analyzed through a series of characterizations,and its antibacterial properties were tested by the dilution coating plate method.It was found that it has good antibacterial properties against Escherichia coli,Staphylococcus aureus and methicillin-resistant Staphylococcus aureus.After analyzing its antibacterial mechanism,it was found that the composite material destroyed the bacterial membrane and further damaged the internal cytoplasm of the bacteria,leading to the death of the bacteria.(2)Chitosan was used as the main raw material and cross-linked with polyvinylpyrrolidone to prepare chitosan hydrogel under acidic conditions.Furthermore,the chitosan hydrogel was loaded with silver sulfide nanoparticles and carbon quantum dots,and the CS/Ag₂S/CQDs hydrogel composite film was prepared.The composition and microscopic morphology of the hydrogel were analyzed by FTIR,TGA,SEM,XPS and other characterization methods.The water absorption performance,in vitro degradation performance,and contact angle of the hydrogel was tested.The results prove that the hydrogel has good swelling and hydrophilicity.Using Escherichia coli and Staphylococcus aureus to represent gram-negative bacteria and positive bacteria,respectively,and methicillin-resistant Staphylococcus aureus to represent drug-resistant bacteria.The antibacterial activity of the hydrogel was tested,and the hydrogel was found to be against three types of bacteria all have good antibacterial properties.The prepared hydrogel is promising as a wound dressing to avoid wound infection caused by bacteria.(3)The g-C₃N₄ was formed by simple heat treatment of melamine,and silver sulfide and carbon quantum dots were loaded on g-C₃N₄ by in-situ growth method to prepare g-C₃N₄/CQDs/Ag₂S photocatalytic antibacterial material.Since the conduction band position of Ag₂S is lower than the conduction band position of g-C₃N₄,the photogenerated electrons of the g-C₃N₄ conduction band can be transferred to Ag₂S,resulting in the effective separation of photogenerated carriers,which can solve the easy recombination of g-C₃N₄ photogenerated electrons and holes.Besides,because CQDs have excellent electrical conductivity,they can provide a path for electron transfer,which leads to the rapid transfer and effective separation of charge carriers.The composition and microscopic morphology of g-C₃N₄/CQDs/Ag₂S were tested through a series of characterizations,and the photo-generated carrier transfer and recombination phenomena in the g-C₃N₄/CQDs/Ag₂S composites were further analyzed by photocurrent response and electrochemical impedance.The photocatalytic antibacterial performance was tested under 4 h light conditions,and the results showed that it has good antibacterial performance for common pathogenic bacteria and drug-resistant bacteria.