Research About Lanthanum Cobaltate-based Perovskite Nanocomposites And Its Related Light-driven Antibacterial Performance

As an important member of perovskite materials,lanthanum cobaltate(LaCoO3)is widely used in batteries,catalysis,energy storage,and optoelectronic devices due to its unique physical and chemical properties.However,the disadvantages,such as the narrow light absorption range and easy compounding of electron-hole pairs,greatly limit the development of LaCoO3 in the field of photocatalysis.In addition,as a novel and low-cost photocatalyst,little research has been reported on LaCoO3-based perovskite materials in the field of antibacterials.Based on the above problems,this work aims to design LaCoO3based nanomaterials with efficient antibacterial performance by modifying the microstructure through metal ion doping,constructing heterojunctions,and investigate its related antibacterial mechanisms in detail.The main research contents are as follows:(1)Ce,Al element co-doped LaCoO3-based nanomaterials(La1-xCexCo1yAlyO3)with sizes ranging from 20 to 50 nm were successfully prepared by the sol-gel method.The optical test results show that the introduction of Ce,Al ions can effectively reduce the band gap and improve the optical absorption efficiency,carrier separation,and transmission efficiency of LaCoO3-based nanomaterials.In addition,Ce,Al co-doping induces a large number of oxygen vacancies(Vo)in the body and surface of the nanomaterials,and the presence of Ce3+/Ce4+can effectively promote electron transfer.The antibacterial experimental results showed that the La0.9Ce0.1Co0.9Al0.1O3 nanomaterials exhibited better antibacterial activities than pure LaCoO3.Its antibacterial efficiency against Escherichia coli(E.coli)reached to 98.8%,which was well correlated with the concentration of doping elements and oxygen vacancies.The enhanced interaction of bacteria and La0.9Ce0.1Co0.9Al0.1O3 with the large specific surface area effectively promotes the generation of reactive oxygen species and improves the transport pathway of released ions.DFT+U calculations further confirm that the Ce,Al co-doping can promote the formation of oxygen vacancies in LaCoO3.The oxygen vacancies on the crystalline surface of La0.9Ce0.1Co0.9Al0.1O3(012)act as electron traps and adsorption activity centers,which can promote the redox process of water molecules(H2O)and oxygen molecules(O2)while generating more reactive oxygen species(ROS:·OH and ·O2-),and thus achieve high light-driven antibacterial performance.(2)Self-assembled LaCoO3 microspheres were prepared by a simple solvothermal method.Subsequently,the highly efficient antibacterial LaCoO3/Ag3PO4 nanocomposites were successfully prepared by loading Ag3PO4 nanoparticles on the surface of self-assembled LaCoO3 microspheres by in-situ precipitation method.The results showed that the self-assembled LaCoO3 microspheres were composed of many nanoparticles,and their porous structure was favorable for the loading of Ag3PO4 particles.Compared with pure LaCoO3 microspheres,the introduction of Ag3PO4 nanoparticles could effectively enhance the antibacterial performance of LaCoO3/Ag3PO4 nanocomposites.The minimum inhibitory concentrations(MIC)of LaCoO3/Ag3PO4 nanocomposites against Escherichia coli(E.coli)and Staphylococcus aureus(S.aureus)reach to 0.1 mg·mL-1 and 0.15 mg·mL-1,respectively.The antibacterial efficiency of LaCoO3/Ag3PO4 nanocomposites against E.coli and S.aureus under visible light irradiation for 20 min was 99.9%and 98.3%,respectively.This was attributed to the enhanced photoresponsiveness,carrier separation,and transmission efficiency of LaCoO3/Ag3PO4 heterojunctions,which greatly promoted the production of ROS under visible light.ROS can interact with bacterial intracellular nucleic acids and enzymatic proteins,causing its irreversible damage.In addition,the strong oxidation of glutathione(GSH)by LaCoO3/Ag3PO4 nanocomposites causes the failure of the antioxidant defense system of bacteria.Furthermore,Ag+release and the Ag plasma effect are also important reasons for LaCoO3/Ag3PO4 nanocomposites to achieve high antibacterial efficiency.(3)ZIF-67 was synthesized by a simple precipitation reaction.Then it was modified by La3+ etching(La3+/ZIF-67)and calcination to obtain LaCoO3/Co3O4 nanocomposites.Subsequently,LaCoO3/Co3O4/g-C3N4 nanocomposites with visible light enhanced antibacterial performance were successfully prepared by compounding LaCoO3/Co3O4 nanocomposites with the nonmetallic semiconductor g-C3N4 by wet impregnation method.Compared with LaCoO3/Co3O4 nanocomposites,LaCoO3/Co3O4/g-C3N4 nanocomposites exhibited stronger carrier transport and separation efficiency,as well as excellent antibacterial properties.The MIC of LaCoO3/Co3O4/g-C3N4 nanocomposites against E.coli and S.aureus was 0.8 mg·mL-1 and 0.9 mg·mL-1,respectively.The antibacterial efficiency of nanocomposites against E.coli and S.aureus under UV light was 99.76%and 96.28%,and 99.64%and 95.66%under visible light.This is attributed to the outstanding visible light response properties of LaCoO3/Co3O4/g-C3N4,which can significantly enhance ROS generation under visible light.In addition,the strong positive charge of the LaCoO3/Co3O4/g-C3N4 nanocomposite(+4.84 mV)facilitates adequate contact between the nanocomposite and bacteria,which greatly shortens the ROS transport pathway.The GSH oxidation simulating the internal metabolism of bacteria revealed that the LaCoO3/Co3O4/g-C3N4 nanocomposites were able to disrupt the antioxidant defense system of bacteria,which eventually led to bacterial apoptosis.