Preparation,Characterization And Application Of Attapulgite Silver-Loaded Composite Antibacterial Material

At present,antibiotic drugs are widely used.On the one hand,they protect people from the harm of some pathogens.On the other hand,they also increase the drug resistance of pathogens,which in turn weakens the efficacy of antibiotics.Therefore,there is an urgent need for an antibacterial substance that can not produce resistance during the antibacterial process.Nano-silver(Ag NPs)and composite materials with nano-silver as the main antibacterial substance show broad-spectrum,high-efficiency,and non-resistance characteristics in the antibacterial field,which has become a research focus in recent years.However,the preparation of nano-silver often requires the introduction of a large amount of reducing agents and stabilizers,which is prone to secondary pollution.At the same time,many nano-silver composite materials have problems such as low silver loading,fast silver loss and poor stability.In this study,based on the characteristics of dopamine(DA)self-polymerization to form polydopamine(PDA),which was used as a reducing agent and stabilizer to synthesize nano-silver particles on the surface of attapulgite(AT)in situ.It has simple preparation conditions and little secondary pollution to the environment.The influence of different influencing factors(p H value,silver nitrate concentration,temperature)on the loading of silver in the composite antibacterial material was investigated.Using Fourier transform infrared spectroscopy(FT-IR),X-ray photoelectron spectroscopy(XPS),X-ray diffraction(XRD)and Zeta potential to characterize and analyze the physical and chemical properties of composite antibacterial materials.The antibacterial performance of the composite antibacterial material was preliminarily explored through the minimum inhibitory concentration(MIC)and the bacteriostatic zone experiment,and the antibacterial curve was used to explore the mechanism of the influence of nano-silver particle size and silver form on the antibacterial performance of the composite antibacterial material.(1)During the preparation of the composite antibacterial material,as the p H of the reaction increases,the loading of silver first decreases and then increases,and when the p H>10,the increase in the loading slows down;Increase the concentration of silver nitrate during the reaction,and the loading of silver continues to increase.When the concentration of silver nitrate is greater than 12 mg/m L,the loading of silver increases slowly;During the preparation of the material,the loading of silver was the highest when the temperature was 60?,reaching 68.7 mg/g.(2)The phenolic hydroxyl(-OH)and C-N bond stretching vibration peaks appear in the FT-IR spectrum of PDA-AT and PDA-AT/Ag composite antibacterial materials,and the N1s signal peak appears in the XPS high-resolution spectrum.The results showed that polydopamine was successfully adsorbed on the surface of attapulgite.When p H<10,the XPS spectrum of PDA-AT/Ag composite antibacterial material only has the signal peak of Ag⁰,which corresponds to the characteristic peak of silver appearing in XRD,with the p H value increasing,the characteristic peak gradually decreases.It shows that the silver in the composite antibacterial material exists in the form of nano-silver and the particle size is gradually reduced;When p H>10,the signal peak of Ag⁺appears in the XPS spectrum of the PDA-AT/Ag composite antibacterial material,and it occupies a larger proportion of the signal peak of Ag⁰.Corresponding to the characteristic peak of Ag₂O in XRD,the characteristic peak of Ag⁰basically disappeared.The results show that after p H>10,Ag₂O appears in the composite antibacterial material,the reason may be that the high p H value causes the silver ions in silver nitrate to be converted into Ag OH and then into a stable Ag₂O precipitate;During the material preparation process,the composite antibacterial material XPS without ethylene glycol has a characteristic peak of Ag⁺.The results show that PDA has a certain reduction selectivity,and ethylene glycol is needed as a supplementary reducing agent.Comprehensive analysis results show that the optimal preparation process of the attapulgite silver-loaded composite antibacterial material can choose the preparation parameters of p H=10,reaction temperature of 60?,and silver nitrate concentration of 12 mg/m L.(3)The results of the inhibition zone experiment show that AT and PDA-AT materials have no antibacterial effect on E.coli and S.aureus.A clear and transparent zone of inhibition appeared around the PDA-AT/Ag composite antibacterial material;The minimum inhibitory concentration(MIC)of the PDA-AT/Ag-p H10 composite antibacterial material against E.coli and S.aureus were 12.8?g/m L and 25.6?g/m L,respectively;The results of the antibacterial curve show that PDA-AT/Ag-p H10 has a stronger antibacterial effect than PDA-AT/Ag-p H8 and PDA-AT/Ag-p H12 under the same silver concentration.The results show that the smaller the nano-silver particle size in the composite antibacterial material,the better the antibacterial performance.At the same time,the presence of Ag2O in the material affects the antibacterial properties of the composite material.(4)Through the investigation of the silver ion release rate of the PDA-AT/Ag composite antibacterial material,it is found that the release rate of the PDA-AT/Ag-p H10material is faster than that of other experimental groups.The silver ions released 17.1%in10 days,and the release performance is good.The slow release of nano-silver can increase the durability of the composite antibacterial material.However,combined with the analysis of the antibacterial experiment results,it can be known that too low silver release rate will affect its antibacterial performance.