Papers by Keyword: Visible Light

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Authors: Li Ya Wang, Qing Li, Xiu Kai Li
Abstract: Bi5AgM4O18 (M=Nb and Ta) photocatalysts with 3.07-3.55eV of band gaps and layered perovskite-like structures showed activities for 2-propanol degradation in gas phase. Due to the appropriate crystal structure and energy band structure, Bi5AgNb4O18 performed much better than Bi5AgTa4O18 for 2-propanol photodegradation.
Authors: J. Theerthagiri, R.A. Senthil, J. Madhavan, B. Neppolian
Abstract: The graphitic carbon nitride (g-C3N4) materials have been synthesized from nitrogen rich precursors such as urea and thiourea by directly heating at 520 °C for 2 h. The as-synthesized carbon nitride samples were characterized by x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), ultraviolet-visible (UV-vis) absorption spectroscopy, photoluminescence (PL) and particle size analysis. The photoelectrochemical measurements were performed using several on-off cycles under visible-light irradiation. The x-ray diffraction peak is broader which indicates the fine powder nature of the synthesized materials. The estimated crystallite size of carbon nitrides synthesized from urea (U-CN) and thiourea (T-CN) are 4.0 and 4.4 nm respectively. The particle size of U-CN and T-CN were analysed by particle size analyser and were found to be 57.3 and 273.3 nm respectively. The photocatalytic activity for the degradation of the textile dye namely, direct red-81 (DR81) using these carbon nitrides were carried out under visible light irradiation. In the present investigation, a comparison study on the carbon nitrides synthesized from cheap precursors such as urea and thiourea for the degradation of DR81 has been carried out. The results inferred that U-CN exhibited higher photocatalytic activity than T-CN. The photoelectrochemical studies confirmed that the (e--h+) charge carrier separation is more efficient in U-CN than that of T-CN and therefore showed high photocatalytic degradation. Further, the smaller particle size of U-CN is also responsible for the observed degradation trend.
Authors: Chih Ling Huang, Yu Bin Chen, Yu Lung Lo
Abstract: Chitosan, β-glycerophosphate, and glycerol are all biocompatible materials for biomedical application. This work successfully developed a thermosensitive hydrogel composed of CS, β-GP and glycerol. The CS/β-GP/glycerol hydrogel can be made as a transparent solution at room temperature and becomes an opaque and turbid hydrogel after heating. The transmission of visible light at different temperature can be measured by a visible micro spectrophotometer combined with a precise temperature control of the demountable liquid cell. A tunable transmission of visible light hydrogel was developed. Moreover, the composition of such hydrogel is safely used and it is potential for biomedical applications.
Authors: Jin Hong Xia, Guo Cheng Han, Guo Yin Huang, Ran Chen
Abstract: Wool spherical-like Bi2WO6 nanoarchitectures were synthesized by hydrothermal method with using bismuth nitrate and sodium tungstate as raw materials. Ag was deposited on the surface of Bi2WO6 by a photoreduction process. The as-prepared products were characterized by XRD, and TEM. The XRD results revealed that the products have neglectable change in crystal with or without Ag, but obvious change in shape and intensity with different hydrothermal process time and optimal time is 12 h at 180 C. The TEM results shown that 7 h was chose as optimal hydrothermal process time. Rhodamine (RhB) and Light Green SF Yellowish (Light green) were chose as objects to evaluate the photocatalytic activities of the products under different light irradiation. The results showed that Ag loading greatly improved the photocatalytic activity of Bi2WO6. Meanwhile, the source of light is a very important affected factor for the photocatalyst degradation, ultraviolet light has the best efficiency, but visible light was chose as the light source finally due to conservation of energy and efficiency. The dynamic behavior of Ag-loaded Bi2WO6 photocatalyst degradation of two pigments obeys pseudo-first-order kinetics at 298 K. The as-synthesized photocatalysts are stable for degradation of two pigments and can be easily recycled.
Authors: Yu Dong Zhang, Xun Jia Su, Gen Liang Hou, Song Bi, Feng Guo, Zhen Xing Mei
Abstract: Visible-light-induced BiVO4-SiO2 composites photocatalysts with monoclinic scheelite structure were successfully synthesized via a sol-gel method, and were characterized with XRD, XPS, DRS, SEM and BET. The result indicated that BiVO4-SiO2 composite photocatalysts exhibited relatively high BET surface areas, consisting of primary nanocrystals with average size of 44 nm. The band gap of the sample was estimated to be 2.56 eV, representing an obvious blue-shift compared with that of the SSR-BiVO4 sample. The photocatalytic activities were also evaluated by decolorization of methylene blue (MB) under blue light. The photodegradation rate of BiVO4-SiO2 composite photocatalysts was quite high, up to 69% in 2 h, which was much better than that of the reference sample prepared by solid-state reaction (5.5%) under the same conditions.
Authors: Zheng Liu, Su Mei Cui, He Yin, Yu Chi Lin
Abstract: Image measurement is a common and non-contact dimensional measurement method. However, because of light deflection, visible light imaging is influenced largely, which makes the measurement accuracy reduce greatly. Various factors of visual measurement in high temperature are analyzed with the application of Planck theory. Thereafter, by means of the light dispersion theory, image measurement errors of visible and infrared images in high temperature which caused by light deviation are comparatively analyzed. Imaging errors of visible and infrared images are proposed quantitatively with experiments. Experimental results indicate that, based on the same imaging resolution, the relative error value of visible light image is 3.846 times larger than infrared image in 900°C high temperature. Therefore, the infrared image measurement has higher accuracy than the visible light image measurement in high temperature circumstances.
Authors: Yin Hu, Dan Zhen Li, Guang Can Xiao, Yu Shao
Abstract: A CTAB-assisted microwave hydrothermal method was used to synthesize BiVO4 photocatalysts with different shapes. The obtained products were characterized by powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), UV-vis diffuse reflectance spectroscopy (DRS). The results showed that the monoclinic phase BiVO4 polyhedron was formed via a tetragonal zircon-type BiVO4 precursor. UV-vis diffuse reflectance spectra showed a great shift to longer wavelengths in the visible region for the monoclinic phase BiVO4 samples compared to the BiVO4 precursor. The photocatalytic activity of the sample was investigated for the liquid phase photocatalytic degradation of RhB under visible light irradiation (λ>420nm). The effects of different reaction times on the photocatalytic activity of BiVO4 had also been investigated, and the highest efficiency was observed when the sample was prepared at 140 °C for 30min.
Authors: Gang Li, Yan Sheng Li, Ying Wang, Hong Gao
Abstract: Nano-ZnO, nano-TiO2 and their mixed catalyst respectively degrade methyl orange solution with concentration 10mg/L in sunlight. When the dosing quantity is 1g/L during 8h degradation, the degradation effect is better and the degradation rates of three catalysts can all reach more than 93% with prolonging of degradation time, and the degradation effect of mixed catalyst is best and its degradation rate reaches more than 99%. Moreover the effect of TiO2 content in the mixed catalyst on catalytic degradation isn’t distinct.
Authors: Xiao Song Zhou, Bei Jin, Bin Yang
Abstract: Cu(OH)2/N-TiO2 compound heterojunction photcocatalyst was prepared via a facile precipitation method. The as-synthesized samples were characterized by means of X-ray diffraction (XRD), field-emission transmission electron microscope (FE-SEM), ultraviolet-visible light (UV-vis) absorbance spectra technologies. The results suggest the as-obtained samples are spherical structure with the diameter of approximately 10-20 nm, the absorbance intensity in the visible light range increased with the amount of deposited increased. Photocatalytic activities of samples were investigated under visible light and methyl orange (MO) acted as simulation pollutants. The catalytic ablity of the synthesized photocatalysts under visible light irradiation showed higher than that of N-P25(TiO2). The remarkable photocatalytic activities are due to the high-quality of composites structure and the driving force for electron transfer in nanoparticle.
Authors: Pongsaton Amornpitoksuk, Sumetha Suwanboon
Abstract: The co-effect of PO43- and I- on the formation of a heterosturucture photocatalyst in the Ag3PO4-AgI system was studied by the co-precipitation method between AgNO3 and the precipitating agent. The precipitating agent was prepared by varying the mole ratios between Na2HPO4 and KI. At 10 mol.% KI, the product showed the mixed phase between Ag3PO4 and un-identified phase. For 30 - 90 mol.% KI, the un-identified phase and AgI were detected in the x-ray diffraction patterns. The un-identified phase strongly adsorbed the methylene blue dye. The product prepared from 30 mol.% KI had the highest content of un-identified phase and also showed the highest degree of decolorization in the dark. The photocatalytic properties of products in this system were confirmed by the decolorization of methylene blue under visible illumination.
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