Preparation And Antimicrobial Properties Of Doped Zinc Oxide Nanocomposites

Bacterial resistance is a major problem that threatens human health in today's society.The development and application of new inorganic antibacterial materials have become a hot topic of attention.In particular,inorganic antibacterial composites have become the focus of current research because of their advantages of effectively avoiding the defect of single component and playing a synergistic role.As an important semiconductor photocatalyst,nano-ZnO has attracted extensive attention due to its low cost,high REDOX potential,non-toxic and environment-friendly properties.Although nano-ZnO has many excellent properties,its antimicrobial efficiency is low when its dosage is low,which seriously restricts its application in antimicrobial field.In order to solve the above problems,in this paper,nano-sized zinc oxide was modified by doping a small amount of metal oxides,which greatly improved the antibacterial activity of nano-sized ZnO.The structure,composition and optical properties of the ZnO composites were characterized by SEM,TEM,XRD,XPS and UV-Vis DRS,respectively.The antimicrobial properties of the composites were evaluated by plate counting method,and the mechanism of antimicrobial activity was explained.Finally,the prepared composite material was applied to hydrogel film antibacterial dressing.The thesis is mainly divided into the following three parts:1.The Cu₂O/ZnO nanocomposites were prepared by chemical precipitation method using ZnO nanoparticles as the substrate,EDTA as complexing agent and ascorbic acid as reducing agent.The composite material significantly improved the antibacterial activity of nano-sized zinc oxide,thereinto,the sample possessing 5 mol%Cu₂O showed great antibacterial activity against Staphylococcus aureus and Escherichia coli.In a certain range,its antibacterial activity increased with the increase of Cu₂O doping amount.Based on the systematic study of the effect of Cu₂O loading on the antibacterial activity,the antibacterial activity of Cu₂O/ZnO composites under dark and natural light conditions was studied.According to the results of the capture of active species,Zeta potential test and ion release experiment,the mechanism of antibacterial activity was explained.In addition,the antibacterial properties of copper doped ZnO nanocomposites with different valence states(Cu₂+,CuO,Cu₂O,Cu0)were also compared.2.Considering the energy band structure between ZnO and BiOI,Nano-ZnO was mixed with newly generated bismuth iodoxide nanosheets under normal temperature and pressure by swelling of nano-ZnO in aqueous medium.A photocatalytic antibacterial nanocomposite—P-N type BiOI/ZnO heterojunction composite was constructed.The antimicrobial activity of BiOI/ZnO composites was investigated under natural light and simulated sunlight irradiation strips.The results showed that,compared with ZnO and BiOI,BiOI/ZnO composites exhibited better antibacterial activity against Staphylococcus aureus and Escherichia coli under simulated sunlight irradiation,and also have better photocatalytic degradation of Rhodamine B(RhB).In addition,the photocatalytic degradation of RhB by BiOI/ZnO composites was studied.According to the results of the capture of active species,Zeta potential test and ion release experiment,the possible antibacterial mechanism of the composites under light conditions was discussed.3.In order to apply Cu₂O/ZnO and BiOI/ZnO nanocomposites with excellent antibacterial properties obtained in the first two parts,two kinds of hydrogel membrane dressings were prepared in combination with sodium carboxymethyl cellulose(CMC-Na).The morphology,structure and composition of hydrogels film were characterized and analyzed by SEM,FT-IR and EDS.The antibacterial activity of the hydrogel film dressing against Staphylococcus aureus and Escherichia coli was also studied,the results showed that Cu₂O/ZnO and BiOI/ZnO composites still maintained good antibacterial activity in the hydrogel film.The experimental results of contact Angle and swelling rate show that the hydrogel film with composite material has good water absorption.In addition,the test of mechanical properties showed that adding composite material could significantly improve the tensile strength of the hydrogel film.The cytotoxicity test proved that the hydrogel membrane had good biocompatibility,and the antibacterial hydrogel film prepared had a good application prospect.