Study On Preparation And Properties Of Composite Particles Based On Nanoscale Zinc Oxide

Zinc oxide?ZnO?with nanoscale has been widely used in many fields,such as cosmetics,medicine,water treatment and textile industries,because of their excellent antibacterial and optical properties.However,since nanosale particles have high surface energy and there is strong van der Waals force between them,ZnO nanoparticles?ZnO NPs?are prone to agglomeration,resulting in a significant decrease in their performance.On the other hand,ZnO NPs inevitably produce reactive oxygen species?ROS?while shielding ultraviolet?UV?rays in certain application fields,such as sunscreen,which could cause oxidative damage to the skin and even lead to skin cancer.In order to overcome disadvantages above,the preparation of composite particles based on nanoscale ZnO has become a hotspot in the field of materials science.The composite particles can not only improve the dispersion stability and intrinsic properties of ZnO nanoparticles,but also endue them with some new functional properties.Therefore,in order to simplify the preparation method and control material structure,this thesis takes the preparation and performance research of composite particles based on nanoscale ZnO as the research direction,and tries to improve the performance of composite materials.The specific work is as follows:?1?Facile preparation and properties of polystyrene?PS?/ZnO composite particles.Herein a facile method is proposed to assemble of ZnO NPs on the polyvinylpyrrolidone?PVP?stabilized PS microspheres to form raspberry-like PS/ZnO composite particles.Specifically,in a mixed system containing ZnO nanoparticle precursors and PS microspheres,the former effectively adsorb on the surface of PS microspheres;subsequently,ZnO nanoparticles are in situ anchored on the surface of the PS microsphere after adding the alkaline solution to obtain PS/ZnO composite particles with raspberry-like structure.Notably,neither complex surface modification nor functionalization is required for the preparation of PS microspheres or ZnO NPs,so the whole preparation process is particularly simple.In addition,based on the analysis of the preparation process and formation mechanism,the size and mass loading of ZnO NPs on the PS microspheres can be easily tuned by varying the concentrations of Zn?Ac?₂·2H₂O,reaction temperatures and the concentrations of NaOH.Finally,due to better stability of them,ZnO nanoparticles fixed on the surface of PS microspheres could produce higher amount of ROS,which made the resultant PS/ZnO composite particles exhibit extraordinary antibacterial activity against both gram-positive Staphylococcus aureus and gram-negative Escherichia coli.?2?Fabrication and properties of ZnO@Ceria?ZnO@CeO2?hollow microspheres.Herein the sacrificial template method is adopted to fabricate ZnO@CeO2 hollow microspheres with reverse bumpy ball structure,which means that ZnO NPs are encapsulated in the internal surface of CeO₂ shell.To be specific,cerium nitrate is added into the as-prepared PS/ZnO composite particle dispersion solution obtained in the previous chapter.Based on electrostatic interaction,cerium ions will spontaneously adsorb on the surface of PS/ZnO composite particles.Furthermore,precipitants are introduced into system above,to obtain PS/ZnO@CeO2 composite particles after in situ reaction.Finally,the ZnO@CeO2hollow microspheres with reverse bumpy ball structure are obtained after removal of PS microspheres by calcination.Different from the traditional sacrifice template method,the preparation process proposed in this chapter is very simple because it does not require any specific surface pretreatment of PS microspheres or PS/ZnO composite particles.In addition,the thickness and composition(the ratio of Ce³⁺/Ce⁴⁺)of CeO₂ shell could be effectively regulated by changing the concentration of cerium?III?nitrate hexahydrate and precipitants.Then the UV shielding performance and free radical scavenging capacity of ZnO@CeO₂hollow microspheres can be regulated.On this basis,the DPPH free radical scavenging experiment,TA hydroxyl radical capture experiment and NBT superoxide anion radical capture experiment confirmed that ZnO nanoparticles can produce ROS under UV radiation,while ZnO@CeO₂ hollow microspheres have the ability to scavenging ROS.Finally,human skin fibroblasts are used as models and the results show that ZnO@Ce O₂ hollow microspheres have excellent cellular compatibility to protect cells from UV radiation damage and reduce the oxidative pressure in the extracellular environment.