| ZnO is an important kind of semiconductor nanocrystals.The research and application of ZnO nanocrystals in photoelectric conversion materials,biological detection and antibacterial materials have attracted much attention due to its obvious quantum size effects,good biocompatibility,mild preparation conditions and low precursor cost.Spherical hexagonal ZnO nanocrystals were prepared by a wet chemical route in alcohol aqueous solution.The influence of precursor and surfactant,solvent,alcohol to water volume ratio,molar ratio of surfactant to precursor,p H and mixing speed on the preparation of ZnO nanocrystals were studied by using sodium dodecyl sulfate,sodium dodecylsulfonate and sodium dodecyl benzene sulfonate as surfactants.The optical properties,size and morphology of ZnO nanoparticles were characterized by UV-Vis absorption spectroscopy,X-ray diffraction(XRD)and transmission electron microscopy(TEM).The results showed that among the three kinds of surfactants,the ZnO nanocrystals has good dispersion and high purity prepared by sodium dodecyl sulfate as surfactant.The ZnO nanocrystals prepared by sodium dodecylsulfonate as surfactant has small particle size,but poor dispersion and low purity.The ZnO nanocrystals prepared by sodium dodecyl benzene sulfonate as surfactant has large average particle size and poor dispersion.The particle size increases and the dispersion becomes worse for ZnO nanocrystals come with the decrease of the alcohol to water ratio and the polarity of the reaction solvent.The formation of ZnO nanocrystals would be inhibited with the increase or decrease of the p H value of the reaction system,and the neutral condition is more conducive to the transformation of ZnO.Water is the direct source of OH-and the reaction of hydrolysis and polycondensation are the main factors determining the reaction rate.The antibacterial properties of UV-treated and non-UV-treated ZnO nanocrystals were investigated by casting plate method.The results showed that the particle size of zinc oxide had little effect on the antibacterial activity of ZnO samples prepared with sodium dodecyl sulfate as surfactant under the condition of no UV light irradiation.The antibacterial effect of zinc oxide on Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli was not obvious in the range of 1×10-3mol·L-1-3×10-3mol·L-1,the antibacterial effect is obvious in the range of4×10-3mol·L-1-6×10-3mol·L-1,the antibacterial rate is about 50%when the antibacterial concentration is 6×10-3mol·L-1.The purity of zinc oxide sample is an important factor affecting its antibacterial performance.The antibacterial performance is proportional to the antibacterial concentration in the concentration range of 1×10-3mol·L-1-6×10-3mol·L-1.The antibacterial performance is directly proportional to the antibacterial concentration of Zn2+can be metabolized by bacteria as an oligonucleotide element under the lower antibacterial concentration,thus promoting the growth of bacteria.ZnO nanocrystals irradiated by UV can produce more reactive oxygen species compared with the samples without UV irradiation,thus showing stronger antibacterial activity. |
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