Study On Preparation And Photoluminescence Performance Of Zinc Oxide Composites

ZnO and its composites have been extensively studied due to their excellent photoelectric properties.This research is based on the current research status that the visible emission mechanism of ZnO is unknown.We innovatively used the near-zero band gap material nickel sulfide(NiS)heterojunction and graphene(r GO)to control the photoluminescence(PL)performance of ZnO.By controlling multiple variables to study the PL properties of ZnO,thereby revealing a visible emission mechanism of ZnO.The main work content is as follows:(1)Firstly,NiS@Ni(OH)₂was prepared by hydrothermal method as the precursor of nickel sulfide heterojunction(Ni_xS_y),and then the mass ratios of NiS@Ni(OH)₂(5%,10%and 20%)compound with ZnO by hydrothermal method,and finally annealing at400?in N₂atmosphere to obtain different Ni_xS_y/ZnO nanorods(NZNRs)composites to study the influence of Ni_xS_yconcentration on the morphologies and PL properties of ZnO.The study found that the 10%Ni_xS_y/ZnO(10NZNRs)composites showed the strongest PL emission,and the addition of Ni_xS_ysignificantly enhanced the ZnO visible emission.After analyzing the results of high-resolution transmission electron microscopy(HRTEM)and solid ultraviolet-visible(UV-vis)absorption,it is found that Ni_xS_ymade the absorption edge of ZnO significantly redshift and narrowed.The morphologies of ZnO in NZNRs were more compact and irregular than that of pure ZnO.Many surface defects introduced by Ni_xS_ymade ZnO green emission significantly enhanced.(2)The preparation of NiS@Ni(OH)₂as the precursor of NiS@Ni O using a method is similar to that of work(1).ZnO/NiS@Ni O(ZNN)composites were prepared by using NiS@Ni(OH)₂with a mass ratios of 10%and various ZnO prepared under different precursor concentrations(ie Zn(CH₃COO)₂·2H₂O:Na OH=1:1;1:5;1:10).The effect of different ZnO precursor ratios on ZnO and ZNN composites PL performances were studied.The study found that as the ratios of Zn(CH₃COO)₂·2H₂O:Na OH increased,that was,the concentrations of Na OH decreased,the crystallinity of ZnO gradually decreased and the internal defects of ZnO improved significantly,and the visible light emission was enhanced.At the same time,pure ZnO prepared under the condition of a ratio of 1:1 exhibited completely different defect types and PL performance compared with 1:5 and 1:10.The ZNN composites prepared by combining various pure ZnO have significantly enhanced the PL intensity compared with pure ZnO,and all ZNN composites exhibited the same type of PL properties.After analysis,it is concluded that NiS@Ni O can effectively shield the emission of some defects,and significantly enhance the green emission of ZnO.(3)On the basis of work(1)and(2),graphene oxide(GO)was successfully prepared by the improved Hummer's method,and it was combined with 10%Ni(OH)₂and ZnO with precursor concentrations of 1:1 to prepare ZnO/NiS@Ni O/r GO(ZNNG)composites through the same method as above.Through the study of the structures and morphologies of ZNNG,combined with X-ray photoelectron spectroscopy(XPS)and electron paramagnetic resonance(EPR),the defect types of pure ZnO,ZnO/NiS@Ni O(ZNN)and ZnO/NiS@Ni O/r GO(ZNNG)were analyzed.The characterization results are compared with the PL behaviors,revealing that the green emission of ZnO in this study originated from the quenching of electrons between the zinc interstitials(Zn_i)and surface oxygen defect levels.A mechanism that NiS@Ni O,r GO can significantly enhance green emissions of ZnO was also prepared.