Synthesis And Antibacterial And Antiviral Properties Of Rare Earth Tungstate High Entropy Ceramic Powder

In our daily life,we are often attacked by various harmful microorganisms,especially bacteria and viruses.Due to the frequent occurrence of microbial infections,the community is very concerned about the development of new long-lasting antibacterial and antiviral materials.In order to enrich the antibacterial and antiviral material system and respond to the demand of new antibacterial materials,tungstate materials are considered to have stable physicochemical properties,high corrosion resistance and friendly to the environment.It is widely used as an important inorganic functional material in the fields of antibacterial,luminescent materials,catalysts,sensors and magnetic materials.In this work,a series of A₂W₃O₁₂（A=La,Sm,Eu,Gd,RE）type rare-earth tungstate high/medium entropy ceramic powders and rare-earth medium entropy oxides were prepared by high-temperature solid-phase synthesis method using tungsten and rare-earth as raw materials,and the antibacterial properties and related physicochemical properties of the materials were investigated,based on which the antiviral properties of the materials were further studied.The high temperature solid phase synthesis method was used to prepare high/medium entropy ceramic powders.The effects of calcination temperature,holding time and temperature rise/fall rate on the final products were investigated to determine the optimal preparation conditions for the products.Through experimental studies,the optimum preparation process for this series of high entropy rare earth tungstate ceramics was determined as follows:the raw materials were mixed in a ball mill for 6 h,then sintered into a phase at 950°C with a temperature rise/fall rate of 2°C/min for 9 h.Finally,the medium plus and three kind of small balls were used for granulation,which can produce monoclinic phase rare earth tungstate high entropy ceramic powders with uniform element distribution,high crystallinity and a concentrated particle size distribution of 1μm.ceramic powder.A comparison of the optimum synthesis temperatures of the single element（1100°C）,the quaternary material（1000°C）and the high entropy material（950°C）shows that the sintering temperature decreases significantly with the increase of the element.This is due to the fact that with the increase of rare earth element species,the internal entropy of the material increases and the thermal movement between molecules intensifies,which is more favorable to the formation of simple solid solution.This indicates that the high entropy design can significantly reduce the synthesis temperature of the material and effectively save energy.Staphylococcus aureus（Gram-positive）and Escherichia coli（Gram-negative）were selected as antimicrobial test strains,and animal viruses H1Nl influenza virus（with envelope）and EV71 enterovirus（without envelope）were used as antiviral test viruses.The results showed that the(La_0.2Sm_0.2Eu_0.2Gd_0.2Ho_0.2)₂W₃O₁₂ high-entropy ceramic powder had the best 24-h antibacterial performance under light-free conditions,and it achieved more than 99.9%antibacterial rate against both bacteria.(La_0.2Sm_0.2Eu_0.2Gd_0.2Ho_0.2)₂W₃O₁₂ and the medium entropy oxide decreased the survival rate of the virus by more than 99%within2 h,indicating that both have excellent antiviral performance.In this study,the ionic solubility of the material and the charged nature of the material surface were investigated to analyze the source of its antimicrobial activity.It was found that the antibacterial properties of the materials were based on the destruction of bacterial biofilms by electrically charged adsorption on the surface of the materials,supplemented by the antibacterial properties of rare earth ions,and that the two were synergistic.Further,the dissolution rates of the materials were evaluated under acid and alkali service conditions and it was found that the high entropy components resulted in lower ion dissolution rates for the high entropy samples compared to the non-high entropy samples due to the hysteresis diffusion effect,indicating that the materials have superior environmental adaptability through high entropy and that the rare earth tungstate high entropy ceramics have better acid and alkali resistance compared to the other samples.In summary,the new rare-earth tungstate ceramic powder prepared by high-temperature solid-phase synthesis method is a broad-spectrum antibacterial and antiviral material with excellent performance and broad application prospects.