Absorption In UV-visible Region Research Articles

Surfactant Assisted Synthesis of BiVO4 by Low Temperature Solvothermal Method: Effect of Calcination for Photocatalytic Activity

A visible light active semiconductor photocatalyst, BiVO4 was synthesized through low temperature solvothermal method in hot air oven followed by calcination. To enhance the degradation rate surfactants were employed, which shows the better degradation for calcinated hexamine added BiVO4, i.e. 74% of methylene blue was degraded in 180 min in visible light irradiation. The result is correlated with lower band gap energy value, i.e. 2.07 eV and lower photoluminescence emission spectra intensity. It was observed the variation in surface morphology of the prepared samples. The specific surface area of calcinated hexamine added BiVO4 was analyzed by BET analysis. All the prepared samples showed higher absorption in UV-visible region. The FTIR confirmed the presence of hexamine in the calcinated hexamine sample.

Solvothermal synthesis, characterization and visible-light-driven photocatalysis of self-assembled flower-like CdS nanostructure

Self-assembled nanorods/nanowires of CdS were successfully synthesized by a solvothermal method at 200 oC for 5, 10 and 20 h using sodium dodecylsulfonate as a capping reagent. X-ray diffraction (XRD) patterns of all CdS samples can be indexed to pure phase of hexagonal CdS structure. The degree of crystallinity of CdS was increased with the increase of holding reaction time from 5 h to 20 h. Transmission electron microscopic (TEM) images revealed that the product synthesized by the solvothermal method at 200 oC for 20 h contained self-assembled flower-like CdS nanostructure. The UV-visible absorption of self-assembled flower-like CdS nanostructure shows excellent absorption in UV-visible region with the absorption peak at 481 nm. Photocatalytic efficiency of the as-prepared CdS samples was investigated through rhodamine B (RhB) degradation under visible light irradiation. In this research, the self-assembled flowerlike CdS nanostructure has the highest degradation of 94.91 % within 80 min.

Chemistry of Natural Dyes of Batik Crafts Colouring Process

By Fixation technique, we found the increasing stability of natural color. The aim of the study was to evaluate the performance of dyes anthocyanin, mangiferin, curcuma longa, Indigi fera and tannin (tingi) in batik dyeing. The medium was optimized by conditioning of natural dyes from amount quantity of extracted dyes in several condition: acid condition, base condition and also complexation during fixation process usually done in Batik dyeing. It was concluded that the color values were found to be influenced by the addition of namely mordants as complexation agent, consequently different fashion hues were obtained from the same dye extract using different mordants. The chemistry aspect such as an absorption in UV Visible region of each dyes and Infra Red absorption have been studied, and also a typical of fixation model should be noticed as a chemistry of dyes.

Synthesis of Cu2(OH)PO4 superstructures with NIR-laser enhanced photocatalytic activity

The development of photocatalysts with wide UV-Vis-near-infrared (NIR) photoabsorption has received tremendous interest for utilizing sunlight efficiently. In this work, Cu2(OH)PO4 superstructures are prepared by a simple hydrothermal route, and they have strong bandgap absorption in UV-Visible region and a distinctive plasmon resonance absorption in NIR region. Under the synergetic illumination of visible light and 980[Formula: see text]nm laser (3.0[Formula: see text]W[Formula: see text]cm[Formula: see text]), Cu2(OH)PO4 superstructures can degrade 89.2% MB with the elevated temperature ([Formula: see text]51∘C) of solution, which is higher than that from visible light group (50.0%), laser group (16.4%), and visible-light/exterior-heating group (62.5%, same temperature at [Formula: see text]51.0∘C). These facts reveal that Cu2(OH)PO4 superstructures exhibit NIR-laser enhanced photocatalytic activity, which not only comes from the photothermal effect-induced temperature elevation, but also mainly results from the increased production of photogenerated electron-hole pairs by NIR-laser. Therefore, Cu2(OH)PO4 superstructures can act as efficient photocatalyst with NIR-laser enhanced photocatalytic activity.

Morphology control of highly efficient visible-light driven carbon-doped POM photocatalysts

Polyoxometallates (POMs) have been extensively adopted as photocatalysts due to the high redox capacity, strong acidity and high thermal stability. However, the water solubility and narrow light absorption in UV-Vis region restrict further application. Towards the above challenges, carbon-doped POMs with different morphologies were successfully prepared via the thermal treatment of urea phosphotungstate and thiourea phosphotungstate in this work. Through carbon doping, the absorption range of POM photocatalysts has been extended to the visible region by introducing mid gap states. The carbon-doped POM photocatalysts exhibit good visible-light photocatalytic activity. The photocatalytic degradation efficiency of imidacloprid with the carbon-doped POM photocatalysts reaches 76.30% with a rate constant of 0.34 h−1. The main reactive species involved in the reaction of imidacloprid photocatalytic degradation are h+ and O2−. The C-doped POM photocatalysts are water insoluble and can be reused with showing a photocatalytic degradation efficiency of 69.59% after 3 times of repetition. This work provides a promising strategy for doping POM photocatalysts.

Optoelectronic Properties of C60 and C70 Fullerene Derivatives: Designing and Evaluating Novel Candidates for Efficient P3HT Polymer Solar Cells.

Ten novel fullerene-derivatives (FDs) of C60 and C70 had been designed as acceptor for polymer solar cell (PSC) by employing the quantitative structure-property relationship (QSPR) model, which was developed strategically with a reasonably big pool of experimental power conversion efficiency (PCE) data. The QSPR model was checked and validated with stringent parameter and reliability of predicted PCE values of all designed FDs. They were assessed by the applicability domain (AD) and process randomization test. The predicted PCE of FDs range from 7.96 to 23.01. The obtained encouraging results led us to the additional theoretical analysis of the energetics and UV-Vis spectra of isolated dyes employing Density functional theory (DFT) and Time-dependent-DFT (TD-DFT) calculations using PBE/6-31G(d,p) and CAM-B3LYP/6-311G(d,p) level calculations, respectively. The FD4 is the best C60-derivatives candidates for PSCs as it has the lowest exciton binding energy, up-shifted lowest unoccupied molecular orbital (LUMO) energy level to increase open-circuit voltage (VOC) and strong absorption in the UV region. In case of C70-derivatives, FD7 is potential candidate for future PSCs due to its strong absorption in UV-Vis region and lower exciton binding energy with higher VOC. Our optoelectronic results strongly support the developed QSPR model equation. Analyzing QSPR model and optoelectronic parameters, we concluded that the FD1, FD2, FD4, and FD10 are the most potential candidates for acceptor fragment of fullerene-based PSC. The outcomes of tactical molecular design followed by the investigation of optoelectronic features are suggested to be employed as a significant resource for the synthesis of FDs as an acceptor of PSCs.

Designing dithienothiophene (DTT)-based donor materials with efficient photovoltaic parameters for organic solar cells.

Three acceptor-donor-acceptor (A-D-A)-type small donor molecules (M1, M2 and M3) were evaluated for optoelectronic properties through density functional theory calculations. These designed molecules consist of a dithieno [2,3-b:3,2-d] thiophene (DTT) donor group linked with 2-(3-methyl-4-oxothiazolidin-2-ylidine)malononitrile acceptor through three different bridge groups. The effect of the donor and three different bridge spacer groups on the designed molecules for opto-electronic properties was evaluated in comparison with the reference molecule R. The reorganization energies of the designed donor molecules suggest very good charge mobility property. The lower value of hole mobility (λh), as compared to electron mobility (λe), revealed that the three designed molecules are best for hole mobility. Frontier molecular orbital (FMO) surfaces confirm the transfer of charge from donor to acceptor unit during excitation. The designed molecules show relatively low HOMO values (in the range of -2.19 to -2.36eV), with strong absorption in UV-Visible region in the range of 459nm to 500nm in chloroform solvent. Electron-hole binding energy results indicate that the designed molecule M2 contains the highest amount of charge, which may dissociate into separate charge easily. Among all the studied molecules, the highest open circuit voltage (Voc) of 3.01eV (with respect to HOMOdonor-LUMOPC61BM) was shown by M3. The open circuit voltages (Voc) of R, M1, M2 and M3 were 2.91eV, 3.01eV, 2.77eV and 3.02eV, respectively. Graphical abstract Three newly acceptor donor acceptor (A-D-A)-based donor small molecules (M1, M2 and M3) were designed by taking dithieno [2,3-b:3,2-d]thiophene (DTT) as a donor group linked with acceptor 2-(3-methyl-4-oxothiazolidin-2-ylidine)malononitrile through three different bridge groups. All the designed molecule were compared with the well-known reference compound R. Optical properties, electronic properties, photophysical and excited state energy were calculated and compared with the well-known, and recently published, reference molecule R . All the newly designed molecules shows good optoelectronic properties with respect to R.

Process development and characterization of centrosymmetric semiorganic nonlinear optical crystal: 4-dimethylaminopyridine potassium chloride

Centrosymmetric semiorganic crystal 4-dimethylaminopyridine potassium chloride (4-DMAPKC) has been grown successfully by using slow evaporation solution growth technique. Powder x-ray diffraction shows the 4-DMAPKC crystal has good crystalline nature. Single crystal XRD shows that the grown 4-DMAPKC is cubic crystal system with cell parameters a = 3.09 Å, b = 3.09 Å, c = 3.09 Å. Investigation has been carried out to assign the Vibrational frequencies of the grown crystal by FTIR spectral studies. UV Visible NIR optical absorption spectral studies in the range of 200–1100 nm shows low absorption in UV Visible region with lower cutoff wave length at 261 nm and optical band gap energy was found as Eg = 5.52 eV. Optically transmittance spectral shows 4-DMAPKC crystal is very good transparency in UV–Visible NIR region. Thermogravimetry and differential thermal (TG-DTA) analysis were carried out. Dielectric studies of as grown crystal sample exhibit low dielectric constant and loss at higher frequencies and attests the nonlinear optical activity. Micro hardness studies of as grown crystal were discussed. Second harmonic generation (SHG) efficiency of the 4-DMAPKC is 0.69 times as that of KDP.

Synthesis of N/Fe Comodified TiO2Loaded on Bentonite for Enhanced Photocatalytic Activity under UV-Vis Light

To improve the efficiency of TiO2as a photocatalyst for contaminant degradation, a novel nanocomposite catalyst of (N, Fe) modified TiO2nanoparticles loaded on bentonite (B-N/Fe-TiO2) was successfully prepared for the first time by sol-gel method. The synthesized B-N/Fe-TiO2catalyst composites were characterized by multiple techniques, including scanning electron microscope (SEM), energy dispersive spectrometry (EDS), X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), X-ray fluorescence (XRF), nitrogen adsorption/desorption, UV-Vis diffuse reflectance spectra (DRS), and electron paramagnetic resonance (EPR). The results showed that bentonite significantly enhanced the dispersion of TiO2nanoparticles and increased the specific surface area of the catalysts. Compared with nondoped TiO2, single element doped TiO2, or unloaded TiO2nanoparticles, B-N/Fe-TiO2had the highest absorption in UV-visible region. The photocatalytic activity of B-N/Fe-TiO2was also the highest, based on the degradation of methyl blue (MB) at room temperature under UV and visible light irradiation. In particular, the synthesized B-N/Fe-TiO2showed much greater photocatalytic efficiency than N/Fe-TiO2under visible light, the newly synthesized B-N/Fe-TiO2is going to significantly increase the photocatalytic efficiency of the catalyst using sun light.

Ultraviolet–Visible Light–Sensitive High Surface Area Phosphorous-Fluorine–Co-Doped TiO2 Nanoparticles for the Degradation of Atrazine in Water

Conventional titanium dioxide (TiO2) materials can be activated only by ultraviolet (UV) light, which is only 4–5% of the whole solar spectrum. As a result, visible light (vis)–active TiO2-based photocatalysts have recently received significant attention in the field of TiO2 photocatalytic treatment and purification of water and air. This study reports the preparation of UV-visible light–active phosphorous (P)-doped, fluorine (F)-doped, and PF–co-doped anatase TiO2 nanoparticles via an innovative sol-gel method. Prepared nanoparticles were characterized by UV-vis diffuse reflectance spectroscopy, X-ray diffraction analysis, Raman spectroscopy, high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy (FTIR), and porosimetry analysis. Synthesized materials exhibited improved structural properties, including high surface area, small crystallite size, reduced band gap energy, mesoporous structure, and high porosity. Due to doping with P and F, light absorption of TiO2 in the visible light region was efficiently enhanced with effective band gap energy of 2.70 eV. Brunauer-Emmett-Teller (BET) surface area for PF–co-doped, P-doped, F-doped, and reference TiO2 nanoparticles was 212.0, 175.0, 88.8, and 79.7 m2/g, respectively. PF–co-doped TiO2 showed the highest photocatalytic degradation of atrazine, which could be attributed to the beneficial effects including small crystallite size, high BET surface area, and light absorption in UV-visible region, induced by co-doping of TiO2 with P and F. Finally, reaction intermediates were determined, which confirms the photocatalytic degradation of atrazine using the synthesized catalysts under UV-visible light illumination.

Estimation of Memantine Hydrochloride Using Ultraviolet-Visible Spectrophotometry in Bulk Drug and Formulation

Memantine HCl (ME-HCl) is a novel class of Alzheimer's disease medication acting on glutamatergic system by blocking NMDA glutamate receptors. ME-HCl is lacking of chromophores or auxochromes, thus it shows no distinct absorption in UV-VIS region. Therefore, no direct UV spectrophotometry method is available for its analysis. Thus, main aim of present study was to develop and validate simple and sensitive UV spectrophotometric method for estimation of ME-HCl and application of validated method for routine analysis of ME-HCl. Me-HCl was converted to free base with ammonia and allowed to react with iodine. The complex formed, shows UV absorptions bands at two wavelengths, 291 nm and 365 nm, but method was validated using 291 nm as λ max . The Lambert-Beer's law is obeyed in range of (10-30 μg/ml). Developed method was found to be linear (r 2 = 0.9999), accurate (102.2 %), precise (% RSD<1 %) and sensitive (LOD = 2.51 μg/ml, LOQ = 7.62 μg/ml). The method was successfully applied to marketed formulation and % purity was found to be 97.17 % w/w.

Preparation of Fluorine-DopedTiO2Photocatalysts with Controlled Crystalline Structure

Nanocrystalline F-dopedTiO2powders were prepared by sol-gel route. The thermal behavior of the powders was recorded by DTA/TG technique. The crystalline phase of the fluorinatedTiO2powders was determined by X-ray diffraction technique. It was demonstrated that F-doping usingCF3COOH favors the formation of rutile along with anatase phase even at low temperature. Moreover, the rutile's phase content increases with the increase of the quantity of the fluorine precursor in the starting solution. The surface area of the powders and the pore size distribution were studied byN2adsorption-desorption using BET and BJH methods. X-ray photoelectron spectroscopy (XPS) revealed that the fluorine is presented in theTiO2powders mainly as metal fluoride in quantities∼16 at %. The F-dopedTiO2showed a red-shift absorption in UV-vis region which was attributed to the increased content of rutile phase in the powders. The powders exhibited enhanced photocatalytic activity in decomposition of acetone.

Efficient Bulk Heterojunction Photovoltaic Cells using Sublimable Transition Metal Complex as Photosensitizers

ABSTRACTMultilayer bulk heterojunction photovoltaic cells using chlorotricarbonyl rhenium (I) bis(phenylimino)acenaphthene (Re-DIAN) complex as photosensitizer were studied. The complex is sublimable, has lower band gap, good thermal stability and good processibility. It has broad absorption in UV-visible region. Therefore, Re-DIAN exhibits good photosensitising property for photovoltaic cells. Multilayer bulk heterojunction photovoltaic cells with simple structures were fabricated base on Re-DIAN complex. The active layer consists of a blend of Re-DIAN and fullerene that were co-deposited in the same layer by vacuum deposition. The photovoltaic properties of the devices were studied by irradiaton under AM1.5 simulated solar light. The effects of changing the co-deposition film thickness, amount of Re-DIAN photosensitizer, and hole transporting materials were studied.

Optical study in a novel quaternary ionic crystal doped with europium

In this Letter, the novel quaternary alkali halide crystal KCl:KBr:RbCl:RbBr doped with europium, each component in a 25% molar fraction and 0.5% of Eu ++, is reported. The value of its refractive index was measured, the crystallographic properties are characterized by X-ray diffractometry, the optical properties were studied by optical absorption in UV-VIS region, and by photoluminescence under N 2 laser excitation at 12 K and at RT. The diffractometer diagram of a powder sample shows a single phase and a well defined value of the lattice constant. From the optical absorption spectra of europium, the value of 10 Dq parameter is obtained, the result is in good agreement with X-rays analysis. It was also observed that decay times of the blue emission is independent of temperature and only one decay component is present in the quenched samples. From obtained data, it is suggested that the symmetry of the Eu ++ site in the quaternary crystal KCl 0.25KBr 0.25RbCl 0.25RbBr 0.25 is similar to a quenched sample of a single component crystal.