Preparation,Fluorescence And Photocatalytic Properties Of La-Doped ZnO Composites

The rare earth La doping ZnO can improve the inherent defects of its nanostructures and improve their photocatalysis and fluorescence properties.In this paper,La-doped ZnO with good photocatalytic properties and La-doped ZnO with fluorescence properties were prepared.The mechanism of La doped ZnO influencing the photocatalytic and fluorescent properties of ZnO was discussed.At the same time,in order to solve the problem that it is difficult to separate and cannot reuse La-doped ZnO in practical applications,Fe₃O₄@SiO₂@ZnO:La nanocomposites were prepared by combining the magnetic and stability functions of Fe₃O₄@SiO₂ core structure and discuss its photocatalytic properties and reusability.1.The La-doped ZnO was prepared by a simple and mild method,and field emission scanning electron microscope(SEM),field emission transmission electron microscope(TEM),X-ray diffraction(XRD)and X-ray photoelectron spectroscopy(XPS)were used to characterize it.The influence of the existence form of La on the structure and properties of ZnO was discussed.At the same time,the performance of La-doped ZnO photocatalytic degradation of dye wastewater was studied with methyl orange as the model molecule.The results show that La-doped zinc oxide can significantly improve the degradation rate of zinc oxide to methyl orange.When the doping amount of La is 5%,the degradation rate of methyl orange reaches 95.2%after 120 minutes of irradiation.2.The zinc oxide quantum dots(ZnO QDs)with good dispersity and stable fluorescence performance were prepared using the solvothermal method,which is simple,easy to control,and applicable to mass production.XRD,TEM,XPS and ultraviolet-visible spectroscopy(UV)were adopted for the characterization,and the effect of alkali concentration and La doping amount on the formation of oxygen vacancy(O_V)of ZnO QDs was investigated.The experiment results showed that the concentration of the O_V of ZnO QDs first increases and then decreases as the alkali concentration rises,and it reaches the maximum when the OH^-:Znmolar ratio is 1:1.It is not conducive to the formation of the O_V of ZnO QDs if the molar ratio of the added alkali is too high or too low.The concentration of the O_V of ZnO QDs goes up with the increase of La doping amount,and it can be effectively controlled by changing the alkali concentration or the La doping amount.Meanwhile,the fluorescence emission intensity of ZnO QDs is in direct proportion to the concentration of O_V,that is,the higher the concentration of the O_V of ZnO QDs,the stronger the fluorescence emission intensity.In addition,89.8%of the fluorescence intensity of the fluorescent quantum dots remained after 5 months at room temperature.3.The Fe₃O₄@SiO₂@ZnO:La microspheres were successfully prepared.The microspheres have the advantages of La-doped ZnO,which can improve the photocatalytic activity of ZnO and the Fe₃O₄@SiO₂ structure can be reused.It was characterized by XRD,SEM,TEM,XPS,and vibrating sample magnetometer(VSM).The effect of Zn²⁺concentration and La doping amount on the photocatalytic performance of Fe₃O₄@SiO₂@ZnO:La microspheres was studied by using methyl orange as the model molecule.The results show that in the preparation of Fe₃O₄@SiO₂@ZnO microspheres,the photocatalytic activity of the microspheres first increases and then decreases with the increase of Zn²⁺concentration.When La is doped,the photocatalysis of Fe₃O₄@SiO₂@ZnO:La microspheres the property increases as the amount of La doping increases.The magnetic photocatalyst not only has high photocatalytic activity,but also can be reused.After repeated use for 5 times,the degradation rate of methyl orange can still reach 81%.The magnetic photocatalyst has potential application prospects in photocatalytic degradation of dye wastewater.