Preparation And Antibacterial Properties Of Silver And Rare Composite Antibacterial Agents

In our daily lives,microbes exist in every corner,and they affect our lives in one way or another.In recent years,in view of safety considerations and awareness of environmental protection,the demand for environment-friendly new non-toxic antibacterial agents is becoming more and more urgent.Therefore,the development of new antibacterial materials is a research hotspot in the field of medicine and materials.Silver nanomaterials are widely used in biomedical field because of their excellent antibacterial properties,broad spectrum,antibacterial durability and non-toxicity.However,silver nanomaterials also have some limitations,such as easy oxidation and agglomeration,and high cost,which limits the potential of its application.In recent years,people have used silver nanomaterials in combination with other carrier materials to prepare new antibacterial materials.Among them,rare earth and silver composite nanomaterials have become hotspots in recent years due to their excellent biocompatibility and broad-spectrum antibacterial properties.The main work of this thesis is the preparation and performance of silver/rare earth composite antibacterial agents.The research contents and conclusions include the following four aspects:?1?Preparation and antibacterial properties of Ag/CeO₂ nano compositeThe cerium oxide?CeO₂?flowerlike structures with large specific surface area were successfully synthesized by solvothermal method,and subsequently in situ formed Ag nanoparticles on the CeO₂ surface to synthesize Ag/CeO₂ micro/nano composites.Their structure and morphology were characterized by XRD,SEM,TEM,FT-IR,zeta potential analyzer and UV-Vis.The results show that most of the prepared Ag/CeO₂ sample is nanoflowers,consisting of nanosheets with a width of 5mm,a length of 10mm and a thickness of less than 100 nm.The size of the supported Ag NPs is 20-40 nm.The antibacterial properties of the samples were tested by broth dilution method and filter paper method.The results show that Ag/CeO₂ composite micro/nano materials have better antibacterial effects against S.aureus and E.coli than single AgNPs under the same reducing conditions.?2?Preparation and antibacterial properties of?Ag/CeF₃?nano compositeThe hydrothermal method was used to successfully synthesize flower-like CeF₃ nanoparticles,and the surface of CeF₃ was further modified with chitosan?CTS?and carboxymethyl chitosan?CMCTS?,followed by adsorbing-reducing Ag ions to produce Ag/CTS/CeF₃ and Ag/CMCTS/CeF₃ composite.The samples were characterized by XRD,SEM,TEM,FT-IR and Zeta potential analyzer.The results show that the Ag/CTS/CeF₃ and Ag/CMCTS/CeF₃ samples present a flower-like structure with a size of 200-300 nm,which consists essentially of nanosheets with a diameter of about 50 nm and a thickness of 10 nm.Since the surface of CeF₃ is modified with CTS and CMCTS,the micro-nano composites have high aqueous dispersibility and long-term dispersion stability.The antibacterial properties of the samples were tested by the sterilization rate method and the filter paper method.The results show that the prepared Ag/CTS/CeF₃ and Ag/CMCTS/CeF₃ composite have excellent antibacterial and bactericidal properties.?3?Preparation and properties of Ag/La-doped titanium dioxide?Ag/mLa/TiO₂? nano compositeAg and Ag/La-doped TiO₂?Ag/TiO₂,Ag/mLa/TiO₂?nanoparticles were prepared by hydrothermal method using tetrabutyl titanate,silver nitrate and lanthanum nitrate as raw materials.The morphology,composition and structure of the samples were carried out by TEM,SEM,XRD and XPS.The results show that the size of La-and Ag-doped TiO₂ sample is smaller than that of the non-doping and Ag-doped TiO₂ sample.For La-and Ag-doped TiO₂ sample,when the doping ratio of La is 0.4%,the particle size is the smallest.Their antibacterial properties were tested by broth dilution method,filter paper method and growth curve method.The results show that the Ag/La/TiO₂ materials have excellent antibacterial properties,and when the doping ratio of La is 0.4%,the material displays the best antibacterial property.?4?Preparation of Ag/La₂O₂CO₃ nano composite and its antibacterial and phosphate-removing propertyLa?OH?CO₃ precursors with different morphologies were prepared by precipitation method using urea and cerium nitrate as raw materials by adjusting different molar ratios of raw materials,followed by calcination in a muffle furnace to obtain La₂O₂CO₃ carrier materials.Then,silver nitrate was used as the silver source to obtain Ag/La₂O₂CO₃ composite by adsorbing-reducing Ag ions on the surface of La₂O₂CO₃.The morphology,elemental and structural analysis of the samples was carried out by SEM,TEM,XRD and XPS.Its removing phosphate property was analyzed by UV-visible spectroscopy.The antibacterial properties of the samples were tested by broth dilution method and filter paper method.The results show that when the molar ratio of La to urea is 1:2,1:6 and 1:55,rod-like,polyhedral block and spindle-shaped La?OH?CO₃ precursors are prepared,respectively,and the spindle-shaped precursor has the smallest size.The spindle-shaped precursor is calcined and loaded with Ag nanoparticles,and the obtained spindle-shaped Ag/La₂O₂CO₃ composite has excellent antibacterial and removing-phosphate properties.