Study On Color, Photoluminescence And Photocatalytic Mechanism Of Multiconductor Synthesized By Irradiation-Assisted Polyacrylamide Gel Method

Semiconductor is a material whose conductivity is between insulator and conductor at room temperature,and its conductivity can be controlled through doping,temperature control and light.Since the discovery of semiconductors in the 1830s,except for the rectification effect,photoconductivity effect,and photovoltaic effect,semiconductors have been found to have photosensitivity,thermal sensitivity,and photocatalytic properties after many years of exploration.Use these characteristics to apply it to sewage treatment,paint,lighting system,communication system and other industries.The physical and chemical properties of semiconductor materials are strongly dependent on their morphology,dimensions,surface defects,grain size and other parameters.Exploring novel synthetic methods for semiconductor materials is great significance for improving the physical and chemical properties of materials.In this thesis,perovskite-type?Y,La,Ce?AlO₃,spinel-type cobalt aluminate?CoAl₂O₄?,and cerium oxide?CeO₂?semiconductors were prepared by gamma-ray-assisted polyacrylamide gel method.Their phase purity,morphology,optics,color,luminescence,electrochemical properties and photocatalytic activity were studied.The specific research content is as follows:?1?Preparation of MAlO₃?M=Y,La,Ce?and YAlO₃:Ce nanomaterials by gamma-ray-assisted polyacrylamide gel method.X-ray diffraction?XRD?results show that the crystallization temperature of MAlO₃ is related to the ionic radius of the trivalent metal ion M³⁺,and the doping of Ce³⁺improves the phase purity,photoluminescence,electrochemical performance of YAlO₃,and also reduces its crystallization temperature.Based on the results of scanning electron microscope?SEM?and transmission electron microscope?TEM?,the surface morphology and crystal structure of aluminate were studied.The color parameters of MAlO₃ pigments were obtained through the CIE model.The calculation results showed that CeAlO₃ was the brightest,which coincided with the actual color.Fluorescence spectrum?PL?results show that CeAlO₃ observes four emission peaks at378,429,468 and 480 nm when the excitation wavelength is 280 nm,and its photoluminescence performance is attributed to 5d¹-4f(²F_5/2.7/2)radiation transition and oxygen vacancy transition to ground state.?2?The irradiation-assisted polyacrylamide gel method was used to prepare the pure phase nano CoAl₂O₄ cobalt blue pigment with an average size of 28 nm.The experimental results show that compared with the sol-gel method polymerized by other methods.Pure cubic CoAl₂O₄ crystals can be obtained by low-temperature sintering at 500?.Fourier infrared spectroscopy?FTIR?analysis showed that three characteristic absorption peaks of CoAl₂O₄ were observed at 668,560 and 504 cm^-1.The chromaticity parameters and optical properties show that the color and band gap of CoAl₂O₄ are largely dependent on the sintering temperature.When the sample was excited with light at an excitation wavelength of 325 nm,two distinct blue light emission peaks appeared at 400 and 430 nm.Based on experimental results and theoretical analysis,the light emission mechanism of CoAl₂O₄ in the presence of organic impurities was explained.?3?Preparation of pure CeO₂ nanoparticles by gamma-ray-assisted polyacrylamide gel method.The oxygen vacancy concentration of CeO₂ nanoparticles increase with the increase of the grain size.The organic functional groups present in the nanoparticles greatly increase their fluorescence characteristics and the adsorption rate of the dyes.But it has nothing to do with degradation of organic dyes.With the increase of the oxygen vacancy concentration,the photocatalytic activity of CeO₂ nanoparticles increases,and its photocatalytic activity strongly depends on the dye concentration and catalyst content.Based on the results of fluorescence experiments and photocatalytic experiments,the photoluminescence mechanism and photocatalytic mechanism were studied.