Zinc Oxide Functional Regulation Based On Doping And Morphology Control

Properties of crystalline materials highly depend on its structural characteristics，including the micro-structure and macro-structure. Doping and morphology control are twomeans to influence the micro-and macro-structure respectively, which may realize thefunctional regulation of ZnO.In this article, based on the theory of crystal defects and crystal growth,F,C-codoped ZnO and ZnO with different morphologies were synthesized by means ofdoping and morphology control. In the doping control, the regulation of photocatalytic andantibacterial properties of ZnO was realized by F and C codoped. In the morphologycontrol, ZnO with different morphologies were adjusted by the precipitant and additiveagent. Photocatalytic activity, the antibacterial property and the thermal catalyticperformances of samples with different morphologies were studied too. In addition, theformation mechanisms of different morphologies were put forward. The main work andachievement are as follows:First, in the doping control, F, C-codoped samples were synthesized by homogeneousprecipitation method. XRD, TEM, XPS, EPR and UV-Vis and so on were performed tocharacterize the structure, morphology, element, defects and band gap of the samples.Besides, photocatalytic activity, antibacterial and thermal catalysis properties were alsostudied. The results are as follows:(1) F, C-codoped ZnO nanoparticles are pure wurtzite phase, the particle size is about30nm, the main forms of F and C are F-Zn, F-C, F-C-F and O-C-O etc.. This is due to theinstead of lattice O by F, while the C replace the Zn lattice sites. FO defect formed by thereplacement of O by F. With the increase of the F doping amount, the concentration of FO defects increases and reaches a maximum at3%.(2) Photocatalytic results shown that the F, C-codoped ZnO has lower photocatalyticproperty than that of pure ZnO, the sample with3%F doping amount behaves the strongestinhibition effect. On one hand, the replacement of lattice O by F leads to the formation of the FOdefect which causes the reduction of oxygen vacancies. On the other hand,passivation effect of F reduce the formation of OS2-/OS-surface state, and thus hinder themovement of photogenerated hole to the surface of ZnO.(3) F, C-codoped ZnO has as good antibacterial property as pure ZnO, which indicatethe photocatalytic mechanism may be not the main antibacterial mechanism of ZnO. Thetest results show that F, C-codoped ZnO samples behave relatively better thermal catalyticperformance, the high temperature decomposition stage disappeared, and the lowtemperature decomposition stage shifted9oC to lower temperature.Second, in morphology control, flow-like, capsule-like and sphere like ZnO wereprepared by precipitation and hydrothermal methods. XRD, SEM, PL, UV-Vis, FT-IR andother characterization method were carried out to characterize the samples. The formationmechanisms of different structure and the performances of the samples were studied. Themain work and achievement are as follows:(1) Cauliflower-like ZnO was prepared by dropping Zn(NO3)2into0.4M NaOHsolution directly. The growth direction of the petals is [0002]. The concentration change ofNaOH only affects the petals, but when changing the dropping direction only, themorphology of ZnO turn to be capsule-like. The difference in nuclear and growth stagewhich affected by the pH value of the reaction solution may be the reason for the formationof different morphologies. PL spectra show that the concentration of oxygen vacancies ofcapsule-like ZnO is significantly higher than that in other samples.(2) Capsule-like ZnO has the best antibacterial and photocatalytic activities, whichmay be related to the oxygen vacancy concentration and exposure of non-polar crystal face.A lot of cracks make the cauliflower-like ZnO rich in oxygen vacancies and active atoms,so it has better photocatalytic and antibacterial properties. Cauliflower like ZnO has abetter thermal optimum catalytic property, the low-temperature decomposition peak shift tolower temperature to290oC。(3) Using TEA, Zn(NO3)2and NaOH as raw materials,2μm spherical ZnO which isassembled by40-60nm particles was prepared by the hydrothermal method. Disorderedassembly leads to the larger number of cracks and cavities on the surface and inside ofZnO sphere. UV-Vis and PL spectra show that sphere-like ZnO prepared with5mL TEAhas the lowest recombination of photogenerated electrons and holes, while the narrowestband gap belongs to the ZnO synthesized by3mL TEA. (4) The photocatalytic activity order of samples prepared with different TEA amountis5mL>3mL>7mL. All the three samples have excellent antibacterial activities, which isbenefited from its good dispersity. Thermal catalytic effect of spherical ZnO prepared by3mL TEA is excellent, the decomposition peak is13oC lower than that of pure AP.Innovation point：Put forward and realize the functional regulation of zinc oxide forthe first time.