25,182 research outputs found
Chemical vapor deposition and characterization of nitrogen doped TiO2 thin films on glass substrates
Photocatalytically active, N-doped TiO2 thin films were prepared by low pressure metalorganic chemical vapor deposition (MOCVD) using titanium tetra-iso-propoxide (TTIP) as a precursor and NH3 as a reactive doping gas. We present the influence of the growth parameters (temperature, reactive gas phase composition) on the microstructural and physico-chemical characteristics of the films, as deduced from X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS) and ultra-violet and visible (UV/Vis) spectroscopy analysis. The N-doping level was controlled by the partial pressure ratio R=[NH3]/[TTIP] at the entrance of the reactor and by the substrate temperature. For R=2200, the N-doped TiO2 layers are transparent and exhibit significant visible light photocatalytic activity (PA) in a narrow growth temperature range (375–400 °C). The optimum N-doping level is approximately 0.8 at.%. However, the PA activity of these N-doped films, under UV light radiation, is lower than that of undoped TiO2 films of comparable thickness
Tests & Calibration on Ultra Violet Imaging Telescope (UVIT)
Ultra Violet Imaging Telescope on ASTROSAT Satellite mission is a suite of
Far Ultra Violet (FUV; 130 to 180 nm), Near Ultra Violet (NUV; 200 to 300 nm)
and Visible band (VIS; 320 to 550nm) imagers. ASTROSAT is a first multi
wavelength mission of INDIA. UVIT will image the selected regions of the sky
simultaneously in three channels & observe young stars, galaxies, bright UV
Sources. FOV in each of the 3 channels is about 28 arc-minute. Targeted angular
resolution in the resulting UV images is better than 1.8 arc-second (better
than 2.0 arc-second for the visible channel). Two identical co-aligned
telescopes (T1, T2) of Ritchey-Chretien configuration (Primary mirror of 375 mm
diameter) collect the celestial radiation and feed to the detector system via a
selectable filter on a filter wheel mechanism; gratings are available in the
filter wheels of FUV and NUV channels for slit-less low resolution
spectroscopy. The detector system for each of the 3 channels is generically
identical. One telescope images in the FUV channel, and other images in NUV and
VIS channels. One time open-able mechanical cover on each telescope also works
as Sun-shield after deployment.We will present the optical tests and
calibrations done on the two telescopes. Results on vibrations test and
thermo-vacuum tests on the engineering model will also be presented.Comment: 9 pages, 7 figures, to be published in Proc. SPIE 8443, "Space
Telescopes and Instrumentation 2012: Ultraviolet to Gamma Ray
The non-linear optical crystal growth and characterization of piperizantum p- aminobentzone
The nonlinear optical properties of piperizanium p – aminobenzoate (PZPAB) crystal were successfully grown with the help of temperature gradient (Slow evaporation) method. The good quality of PZPAB single crystal is formed. The PZPAB is characterized with the help of X-ray diffraction (XRD), Fourier transform infrared (FTIR) measurement, photoluminescence (PL), Raman spectroscopy, ultra violet visible spectroscopy (UV) and finally etching analysis was done.
BIBECHANA 6 (2019) 5-2
Comparison of external bulk video imaging with focused beam reflectance measurement and ultra-violet visible spectroscopy for metastable zone identification in food and pharmaceutical crystallization processes
The purpose of the paper is twofold: it describes the proof of concept of the newly
introduced bulk video imaging (BVI) method and it presents the comparison with
existing process analytical technologies (PAT) such as focused beam reflectance
measurement (FBRM) and ultra violet/visible (UV/Vis) spectroscopy. While the latter
two sample the system in small volumes closely to the probe, the BVI approach monitors
the entire or large parts of the crystallizer volume. The BVI method is proposed as a
complementary noninvasive PAT tool and it is shown that it is able to detect the
boundaries of the metastable zone with comparable or better performance than the FBRM
and UV/VIS probes
Mo and Mn Co-doping for Isoproturon Degradation under Visible Light
This research focused on the improvement of the catalytic efficiency of titanium dioxide using transition metals for isoproturon degradation under visible light. Molybdenum and manganese were varied at 0.5% by weight and 1% by weight. Mo/Mn doped TiO2 was synthesized using sol-gel method and compared with the undoped TiO2 to find out the most suitable doping metal and doping amount for the degradation of isoproturon, a pesticide generally used in agricultural sites. The characterization techniques for all doped TiO2 included N2 physical adsorption/desorption (BET), X-Ray diffraction Spectroscopy (XRD), Ultra Violet -Visible Spectroscopy (UV-VIS), Photoluminescence Spectroscopy (PL), and SEM (Scanning Electron Microscope) –EDX (Energy Dispersive X-ray Diffraction). For each TiO2 catalyst, the photocatalytic degradation of 10 ppm isoproturon was carried out under visible light and the catalytic efficiency was determined using UV-VIS to measure the residual concentration of isoproturon. According to the results, doping molybdenum and manganese assists in reducing the band gap energy, increasing the surface area of catalysts, and enhancing the photocatalytic activity. In case of manganese, it also minimizes the recombination of photogenerated electrons and holes, which leads to better photocatalytic performance. The optimum isoproturon degradation is appeared with the co-doped Mo and Mn at 1% by weight
A measurement strategy for non-dispersive ultra-violet detection of formaldehyde in indoor air: Spectral analysis and interferent gases
We have conducted an extensive review of published spectra in order to identify a region with potential for detection of formaldehyde in indoor air. 85 chemicals and chemical groups common to the indoor environment were identified, 32 of which had absorption spectra in the UV-vis region. Of these, 11 were found to overlap with the formaldehyde UV region. It was found that the region between 320 to 360 nm is relatively free from interference from indoor gases, with NO being the only major interferent. A method is proposed for a low resolution (3 nm) spectroscopic detection method, specifically targeted at formaldehyde absorption features at 327 nm with a reference at 334 nm. 32 ppb of NO was found to have a cross-sensitivity with equivalent magnitude to 100 ppb of formaldehyde. A second reference at 348 nm would reduce this cross-sensitivity.This work was funded by the Engineering and Physics Science Research Council (EPSRC) under grants GR/T18424, EP/P504880 and EP/H02252X. Enquiries for access to the data referred to in this article should be directed to [email protected]
Formaldehyde sensor using non-dispersive UV spectroscopy at 340nm
Formaldehyde is a volatile organic compound that exists as a gas at room temperature. It is hazardous to human health causing irritation of the eyes, nose and throat, headaches, limited pulmonary function and is a potential human carcinogen. Sources include incomplete combustion, numerous modern building materials and vehicle fumes. Here we describe a simple method for detecting formaldehyde using low resolution non-dispersive UV absorption spectroscopy for the first time. A two channel system has been developed, making use of a strong absorption peak at 339nm and a neighbouring region of negligible absorption at 336nm as a reference. Using a modulated UV LED as a light source and narrowband filters to select the desired spectral bands, a simple detection system was constructed that was specifically targeted at formaldehyde. A minimum detectable absorbance of 4.5 × 10-5 AU was estimated (as ΔI/I0), corresponding to a limit of detection of approximately 6.6 ppm for a 195mm gas cell, with a response time of 20s. However, thermally-induced drift in the LED spectral output caused this to deteriorate over longer time periods to around 30 ppm or 2 × 10-4 A
Scalable Preparation of SrTiO3 Submicro-wires from Layered Titanate Nanowires
AbstractSrTiO3 submicro-wires were prepared by the reaction of layered titanate nanowires with Sr (OH)2 powder in an autoclave. The wires were investigated using X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), Ultra-violet visible (UV-vis), photoluminescence (PL) and Raman spectroscopy. The XRD measurement shows that the prepared SrTiO3 submicro-wires hardly have impurity phases. The SEM and TEM images demonstrate that the scalable wires, which need to be processed at the reaction temperature of 180 °C for about 48 hours, are not composed of single crystals. The PL shows that the wire-like SrTiO3 has emission peaks at the wavelengths of 568 and 585 nm. Further, the Raman spectroscopy reveals structural changes in the products through different reaction time
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