Preparation And Fluorescence Properties Of Rare Earth-Heteropoly Acid Based Materials

Polyoxometalates are a kind of unique metal oxide clusters,which have many shapes,sizes,compositions,and unique physical and chemical properties.Energy transfer can occur in some polyacid compounds containing rare earth elements due to the special 4f electron configuration.Therefore,these polyacid compounds which can exhibit well-performed fluorescence properties,have been received wide concern in multifunctional materials and droad application prospect.In this dissertation,polychromatic chitosan films,polychromatic hydrogels and reversible fluorescent switches were fabricated.The morphology,structure and composition of the materials were analyzed by various characterizations including scanning electron microscopy,energy dispersive X-ray spectroscopy,X-ray diffraction,Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy.Besides,the fluorescence properties or electrochemical behaviors of the materials were further examined by fluorescence spectroscopy or electrochemical workstation.First,red fluorescent EuW₁₀,green fluorescent TbW₁₉ and blue fluorescent tetraphenyl ethylene were fabricated.By varying the mass ratios of EuW₁₀,TbW₁₉ and tetraphenyl ethylene,chitosan films with different colors can be obtained.The prepared chitosan film with suitable ratio can exhibit white fluorescence under ultraviolet lamp.Then,ZnWO₄ was employed as the blue fluorescent material,and color-tunable hydrogels with well-performed fluorescence and transmittance can be prepared by adjusting the ratio of EuW₁₀,TbW₁₉ and ZnWO₄.The hydrogel prepared with suitable component ratio can be observed to be colorless and transparent under sunlight and white fluorescent under ultraviolet lamp.Finally,the fluorescent switch system were contructed by assembling EuW₁₀ and PB or WO₃ onto ITO glass,in which EuW₁₀ was used as photoluminescence material and PB or WO₃ as electrochromic material.Reversible transition can be achieved on the fabricated fluorescent switches by applying different voltage and further changing the states of PB or WO)3,which possess the advantages including easy operation and fast response.