Effects Of Different Preparation Conditions On Ultrastructure And Properties Of CuSe/ZnSe Core-Shell Materials

In recent years,the researches on nanomaterials has been increasing gradually.Nanoparticles(NPs),as a kind of zero-dimensional nanomaterials,have attracted extensive attention of scientists due to their unique electrical,optical,thermal and catalytic properties.Among them,?-? semiconductor nanoparticles have been found to have great potential applications in solar cells,sensors,lasers,photocatalysts and biomedical imaging.At present,there are many studies on nanoparticles based on cadmium-based compounds,and the preparation methods are more mature.However,cadmium-based compounds have certain toxicity.As a wide-band gap semiconductor material,zinc selenide(ZnSe)is more suitable for biological applications because of its low toxicity,high water solubility and environmental friendness compared with cadmium compound.In addition,copper selenide(CuSe),as a p-type semiconductor,has a wide range of stoichiometric and non-stoichiometric components,leading to its structural diversity.Pure CuSe with hexagonal phase is stable at room temperature and can be used for degradation of organic pollutants,etc.The application of exposed nanoparticles has some limitations.By growing inorganic wide-band gap shell on the surface of nanoparticles,the surface defects of nanoparticles can be improved,as well as the luminescence performance.In addition,it can increase the stability of nanoparticles in the external environment.Therefore,this paper chose to study ZnSe and CuSe semiconductor nanomaterials.According to a large number of literature searches and relevant reports,there has been no relevant research on the synthesis of CuSe/ZnSe nanoparticles with core-shell structure by ultraviolet irradiation.In this paper,CuSe nanoparticles were synthesized by reflux condensation.After that,using a simple and rapid photochemical method,CuSe/ZnSe nanoparticles with clear core-shell structure were obtained by growth of ZnSe shell on the surface of CuSe nanoparticles under ultraviolet irradiation at room temperature.Different characterization means were used in order to characterize the samples,such as X-ray diffraction spectrum(XRD),energy dispersive spectroscopy(EDS),transmission electron microscopy(TEM),high-resolution transmission electron microscopy(HRTEM),ultraviolet visible absorption spectroscopy(UV-Vis)and photoluminescence spectroscopy(PL).The crystal structure,morphology characteristics as well as optical characteristics of the synthesized CuSe/ZnSe core-shell nanoparticles have been analyzed.Meanwhile,the effects of different preparation conditions on the ultrastructure and optical properties of the synthesized CuSe/ZnSe core-shell nanoparticles were discussed.The detecting results show that the synthesized CuSe nanoparticles belong to the hexagonal phase structure,the particles are spherical with good dispersion,and the particle size is between 6 nm and 16 nm.The decrease of reaction temperature resulted in the low crystallinity of CuSe nanoparticles,and the morphology of the nanoparticles became irregular spherical and the size distribution of particles was not uniform.At the same time,with the increase of reaction temperature,the size of the synthesized CuSe nanoparticles has been decreased.In addition,the test results showed that the particle size of the synthesized CuSe/ZnSe core-shell nanoparticles is about 15-45 nm,and the band gap is higher than that of pure ZnSe or pure CuSe bulk materials,and the fluorescence properties of CuSe nanoparticles were greatly improved by the coating of ZnSe shell.When the molar ratio of zinc and selenium sources in the reactants was changed,the absorption peak of the products has been redshifted with the increase of the ratio,and the fluorescence properties were enhanced at the same time.The size of CuSe/ZnSe core-shell nanoparticles varies with the illumination time.When the illumination time is too short,the core-shell structure of the product is not clear and the luminescence intensity is weak.However,if the illumination time is too long,the nanoparticles are easy to polymerize,the size of nanoparticles increases unevenly,and the surface defects also increase,which results in the decrease of fluorescence intensity again.According to comprehensive analysis and comparison,the optimal growth conditions of the products are as follows: the illumination time is 30 minutes,and the molar ratio of copper selenide,zinc source and selenium source is about 1:2:2.The morphology,structure and fluorescence properties of the synthesized CuSe/ZnSe core-shell nanoparticles under this condition are relatively best.