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How To Correctly Determine the Band Gap Energy of Modified Semiconductor Photocatalysts Based on UV–Vis Spectra
摘要： A misuse of the Tauc plot to determine the band gap energy of semiconductors may lead to erroneous estimates. Particularly large errors can be associated with characterization of modified semiconductors showing a significant absorption of sub-band gap energy photons. Taking the model methyl orange/titanium dioxide system, we address the problem and discuss how to apply the Tauc method correctly.
关键词： band gap energy,UV?Vis spectra,Tauc plot,methyl orange,modified semiconductors,titanium dioxide
更新于2025-09-09 09:28:46
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Highly UV sensitive polycrystalline zinc selenide thin film grown by chemical bath deposition technique
摘要： In this communication, we report a significantly high UV sensitivity of polycrystalline zinc selenide thin films prepared by chemical bath deposition technique. A three order of magnitude of photo current to dark current ratio is obtained for the as-deposited film under UV exposure. However, the photosensivity is found to decrease sharply upon open air isochronal annealing of the sample. The variation of the photocurrent to dark current ratio with annealing temperature is attributed to shrinking diameter of nano-wire like structures exhibited by the films, variation of the band gap energy and a decrease in the grain boundary charge density of the material which collectively enhance the free carrier concentration in the band leading to a substantial loss in the photosensitivity of annealed films compared to the as-deposited film.
关键词： ZnSe thin film,UV sensitivity,SEM,Band gap energy,Optical absorption co-efficient,Grain boundary charge density
更新于2025-09-04 15:30:14
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Crystallographic, optical, and electronic properties of (Cu, Li)GaS2
摘要： We synthesized chalcopyrite-type (Cu1-xLix)GaS2 solid solution samples with a composition of 0.00 ≤ x ≤ 0.20 by mechanochemical process and sequential heating at 550oC in 5% H2S/N2 gas atmosphere. The X-ray powder diffraction (XRD) peaks of (Cu1-xLix)GaS2 shifted by substitution of Li atoms for Cu atoms in CuGaS2. Their crystallographic parameters were refined by Rietveld analysis using XRD data. The lattice constant a of the (Cu1-xLix)GaS2 solid solution increased with increasing Li content, x, while the lattice constant c decreased with increasing Li content, x. We determined band-gap energies of (Cu1-xLix)GaS2 solid solution by diffuse reflectance spectra. The band-gap energy of the (Cu1-xLix)GaS2 solid solution increased from 2.44 eV of CuGaS2 (x = 0.0) to 2.54 eV of (Cu0.8Li0.2)GaS2 (x = 0.2). To understand the band diagram of (Cu1-xLix)GaS2 solid solution, the energy level of the valence band maximum (VBM) was estimated from the ionization energy, which was measured by photoemission yield spectroscopy. The energy level of the conduction band minimum (CBM) was also determined by adding the band-gap energy to the VBM level. The VBM level of the (Cu1-xLix)GaS2 solid solution decreased with increasing Li content, x. On the other hand, the CBM level was approximately constant. Li-doping in CuGaS2 is effective for decreasing the VBM level without increasing the CBM level.
关键词： Mechanochemical process,Band-gap energy,(Cu1-xLix)GaS2,Chalcopyrite-type,Photoemission yield spectroscopy
更新于2025-09-04 15:30:14
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Ethiopian natural zeolites for photocatalysis
摘要： The combination of zeolites and photochemistry has recently shown excellent results due to the special structure of the zeolites that helps a better use of the solar energy improving the selectivity of the chemical reactions carried out. There are several reports on the preparation of TiO2 confined nanoparticles in synthetic zeolites. However, very few reports are found on the use of natural zeolites. Zeolites are a vast natural resource in Ethiopia that remains unexploited. Their microporous structure can accommodate a wide variety of cations such as sodium, potassium and magnesium among others. The main objective of our work was to test the potential use of the naturally occurring zeolites, with high content in titanium, as photocatalysts. The samples have been characterized by X-ray diffraction (XRD), chemical analysis (ICP-OES), scanning electron microscopy (SEM), diffuse reflectance spectroscopy (UV-Vis) and photocatalytic activities of the samples were tested in photocatalytic degradation of methyl orange (MO).
关键词： Natural zeolite,Photocatalysis,Methyl orange,Band gap energy,TiO2 loading
更新于2025-09-04 15:30:14