Preparation And Optical Properties Of Ag Modified ZnO Nanoflowers/Rods

ZnO nanomaterials have a wide range of application prospects in the fields of electricity,optics,magnetism and other disciplines as well as national defense and medical treatment.The controlled growth of ZnO nanomaterials with different morphologies and structures is of great significance to the study of their applications.In the prepared ZnO nanomaterials with various morphisms,the three-dimensional flower-like structure of ZnO can avoid the agglomeration of nanoparticles,increase the specific surface area of ZnO,and improve the nonlinear response and photoluminescence(PL)performance of ZnO nanomaterials.Therefore,it has attracted more and more researchers' attention.In this paper,ZnO nanorods/flowers(ZnO NRs/NFs)were prepared by hydrothermal method,and controlled growth of nano-flower-like ZnO was realized by adjusting the growth time and precursor concentration.In addition,ZnO nanoparticles(AgNPs@ZnO NFs)were synthesized by hydrothermal and magnetron sputtering two-step method.On this basis,the photoluminescence properties and nonlinear optical properties of the samples were studied in detail by means of PL spectrum and Z-scan.Firstly,the effect of morphology of ZnO NFs growing at different concentrations on PL properties was studied,and the growth mechanism of ZnO NFs was analyzed.The effects of structure,morphology,linear and nonlinear optical properties of AgNPs@ZnO NFs were also studied.The main contents are as follows:ZnO NRs/NFs and AgNPs@ZnO NFs were prepared by single-step hydrothermal method and two-step magnetron sputtering method.In this work,ZnO NFs and ZnO NRs with different morphologies were obtained on Ag seed layer and smooth silicon substrate,respectively.The growth mechanism of ZnO nanomaterials was discussed,the influence of precursor concentration on the morphology and structure of ZnO NRs/NFs was analyzed,and the catalytic effect of Ag seed layer on the growth of ZnO nanomaterials was also discussed.The AgNPs@ZnO NFs of different sizes were prepared by adjusting the experimental parameters of magnetron sputtering,and the effects of AgNPs on the structure and morphology of ZnO NFs were studied.The PL performance of ZnO NRs/NFs and AgNPs@ZnO NFs was tested by using PL spectrum.The effect of different AgNPs on PL performance of ZnO NFs was analyzed to reveal its luminescence mechanism.The experimental results show that the AgNPs with a diameter of 10-20 nm cover the defect states on the ZnO NFs surface,which weakens the intensity of visible light,but does not change the structure and morphology of ZnO NFs.AgNPs with a diameter of 18-50 nm can effectively enhance the visible luminescence intensity,which is due to the competitive synergistic effect between the increase of exciton concentration and the enhancement of the local field of metal nanoparticles.The nonlinear optical(NLO)properties of ZnO NFs and AgNPs@ZnO NFs were studied by Z-Scan test using a femtosecond(fs)pulsed laser.The results of open Z-scan with a laser wavelength of 800 nm and pulse width of 190 fs show that the nonlinear absorption of AgNPs@ZnO NFs array is improved with the increase of laser energy.The results of closed Z-scan at a wavelength of 400 nm and a pulse width of 190 fs show that AgNPs@ZnO NFs has a significantly higher nonlinear refractive index than ZnO NFs.AgNPs@ZnO NFs is a kind of nanocomposite with the potential to be developed as a multifunctional optical device.The experimental design and research content of this paper provide the optimal growth parameters for the growth of noble metal modified ZnO nanomaterials,and after modification by AgNPs,the PL properties and nonlinear refraction of three-dimensional flower-like ZnO nanomaterials are improved,which lays an experimental foundation for the application of ZnO nanomaterials.