The micron-sized Sr 2(P2O7):Ce,Tb green phosphors were prepared by being annealed at different temperatures with its precursors synthesized by co-precipitates of(NH4) 2HPO4 at ambient temperature. The phase structure, grain size, surface morphology, and luminescent properties of phosphors were investigated by X-ray diffraction, scanning electron microscope, transmission electron microscope, and fluorescence spectrum. The results show that the product of precursor annealed at 1,100 °C is Sr 2(P 2O7):Ce,Tb, which belongs to orthorhombic phase. The powder is spherical and the size distribution is in micron grade. The sample with the molar ratio of Sr/Tb/Ce of 100.0:0.4:0.6 shows the best fluorescence effect annealed at 1,100 °C for 3 h. The phosphors produce green fluorescence by being excitated with ultraviolet radiation of 254 nm wavelength, and the main emission peak is at 547 nm. The Sr 2(P2O7):Ce,Tb phosphors synthesized by co-precipitation method of precursors at ambient temperature is a kind of efficient green-emitting phosphors.
In this study,CdS/g-C_3N_4(CSCN) heterojunctions were in situ fabricated with a large amount of Cd S nanoparticles anchored on g-C_3N_4 nanosheets.A wet chemical method was developed for the first time to determine the actual content of Cd S in CSCN composites.X-ray diffraction(XRD),Fourier transform infrared spectra(FTIR),high-resolution transmission electron microscopy(HRTEM) and UV-vis diffuse reflectance spectra(DRS) were employed to characterize the composition,structure and optical property of CSCN composites.Based on the isoelectric point(IEP) analysis of g-C_3N_4,a conclusion was obtained on the combination mechanism between Cd S nanoparticles and g-C_3N_4 nanosheets.The photocatalytic activity of CSCN composites was much better than those of individual Cd S and g-C_3N_4 for the degradation of azo dye Methyl Orange(MO) by 40 min adsorption in the dark followed by 15 min photocatalysis under visible light irradiation.After 5 cycles,CSCN composites still maintained high reactive activity with the MO degradation efficiency of 93.8%,exhibiting good photocatalytic stability.The Cd2+concentration dissolved in the supernatant detected by atomic absorption spectroscopy(AAS) of CSCN composites was lower than that of pure Cd S,implying that the photocorrosion of Cd S could be suppressed via the combination with g-C_3N_4.Photoluminescence emission spectra(PL) results clearly revealed that the recombination of photogenerated electron-hole pairs in CSCN composites was effectively inhibited due to the formation of heterojunctions.Based on the band alignments of g-C_3N_4 and Cd S,the possible photocatalytic mechnism was discussed.
为了提高TiO2光阳极的电子传输速率,在TiO2中负载了多壁碳纳米管(MWCNTs)。采用溶胶–凝胶水热法制备了TiO2/MWCNTs复合溶胶,利用电流体动力学方法制备了均匀的TiO2/MWCNTs复合薄膜,并用TiCl4对薄膜进行了优化。用扫描电子显微镜、透射电子显微镜、X射线衍射仪和紫外可见吸收光谱仪对样品进行了表征分析。利用电化学阻抗谱和电流密度–电压曲线分析了基于TiO2/MWCNTs复合光阳极和SnO2/MWCNTs对电极的染料敏化太阳能电池(DSSC)的光电性能。结果表明,MWCNTs的加入极大地加速了电子在薄膜中的传输,减少了电子与氧化态染料和I3–的复合;基于CNT-0.12(质量分数0.12%)复合光阳极的DSSC性能最佳(VOC=0.70 V,JSC=13.0 m A/cm2,ηFF=0.64,η=5.80%),与基于纯TiO2光阳极的DSSC(η=4.44%)相比,能量转换效率提高了30.6%。
