Preparation and Photoelectric Properties of Europium-containing Nanomaterials

Author:Xu Bing Yu

Supervisor:wang guo feng

Database:Doctor

Degree Year:2019

Download:9

Pages:122

Size:14991K

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Rare earth has become an important element in the development of new materials due to its unique physical and chemical properties such as light,electricity and magnetism.It has been widely used in various fields of the national economy.Among them,the nano-material containing rare earth Eu3+ions are good luminescent materials,which are widely used in lighting,optical communication,fluorescent probe and other fields.In addition,europium ions can be used to adjust the band gap structure of semiconductor materials,modify the semiconductor and apply in the field of cells and catalysis.A large number of studies have shown that the properties of nanomaterials are related to the structure and morphology of the nanomaterials.Therefore,the synthesis of rare earth nanomaterials with different sizes and special morphology can obtain some special physical and chemical properties.A series of Eu3+ions doped rare earth nanomaterials were synthesized by selecting several matrix materials such as SrWO4,BiVO4 and Bi2S3.The luminescent properties of the samples and their applications in dye-sensitized solar cells and photocatalysis were systematically studied.The specific research contents are as follows:(1)One-dimensional SrWO4:Eu3+nanomaterials were synthesized by hydrothermal method,and studied the effects of initial reactant concentration and reaction time on the size,morphology and luminescence properties of the samples.When the excitation wavelength is 295 nm,the 5D0→7F1 transition intensity is higher than the5D0→7F2 transition intensity,indicating that Eu3+occupies the position of the inversion center.However,the excitation wavelength is in the range of 363-537 nm,and the5D0→7F2 transition intensity is higher than the5D0→7F1 transition intensity,indicating that Eu3+is at the off-inversion center.It is indicated that the SrWO4:Eu3+nanomaterials have multiple luminescent centers.(2)Using BiVO4 as the host material,the CeOx/BiVO4:Eu3+composite photocatalyst was successfully designed and synthesized by the synergistic effect of Eu3+ions and CeOx.First,we doped the BiVO4 nanosheets with rare earth Eu3+ions.Then,BiVO4:Eu3+and CeOx were composited to construct a composite material.The visible light catalyzed CO2 reduction performance of composites were investigated.The visible light catalytic degradation performance of the composites were studied with2,4-dichlorophenol as the target pollutant.The results show that the proper amount of Eu3+ion doping improves the photocatalytic performance of BiVO4,mainly because the doping of Eu3+ions increases the valence band position and increases the absorption of visible light.When the doping concentration is too high,the photocatalytic performance is weakened due to the formation of the zircon tetragonal phase BiVO4.BiVO4:Eu3+is combined with a certain amount of CeOx.The photocatalytic activity is significantly improved,which is mainly due to the fact that CeOx can be used as a suitable platform to receive high-energy electrons excited from narrow-band semiconductors,thereby prolonging charge life and improving charge separation.(3)The flower-like Bi2S3:Eu3+nanomaterials were successfully prepared by solvothermal method,the luminescence properties of the samples were studied.The composite photoanode of TiO2-Bi2S3 and TiO2-Bi2S3:Eu3+were designed successfully.The results show that the doping of Eu3+can narrow the band gap and increase the specific surface area of visible light of Bi2S3.Compared with pure TiO2 cell,TiO2-Bi2S3:Eu3+cell has higher photoelectric conversion efficiency.When the mass concentration of Bi2S3:Eu3+is 3 wt%,the photoelectric conversion performance is optimal.The results of EIS analysis showed that the interface resistance of TiO2-dye|I3-/I-interface of TiO2-Bi2S3:Eu3+cell was higher than that of pure TiO2 cell.In addition,the TiO2-Bi2S3:Eu3+cell has longer electron recombination time,longer electron transit time,and higher charge collection efficiency than pure TiO2 cell.