Defect-mediated time-efficient photocatalytic degradation of methylene blue and ciprofloxacin using tungsten-incorporated ternary perovskite BaSnO3 nanoparticles.

Photocatalytic water purification has been extensively explored for its economic, eco-friendly, and sustainable aspects. In this study, tungsten (W) incorporated BaSn1-xWxO3 (x = 0 to 0.05) nanoparticles synthesized by facile hydrogen peroxide precipitation route has been demonstrated for photocatalytic degradation of methylene blue (MB) dye and ciprofloxacin (CIP) antibiotic. The structural analysis indicates the presence of hybrid composite-like nanostructures with reduced crystallinity. Optical studies reveal blueshift in bandgap and decrease in oxygen vacancy defects upon W-incorporation. Pure BaSnO3 shows overall enhanced photocatalytic activity towards MB (90.22%) and CIP (78.12%) after 240 min of white LED light and sunlight irradiation respectively. The 2 % W-incorporated BaSnO3 shows superior photocatalytic degradation of MB (26.89%) and CIP (45.14%) within first 30 min of irradiation confirming the presence of W to be beneficial in the process. The free radical study revealed the dominant role of reactive hole (h+) and oxygen radical (O2•-) species during photodegradation and their intermediates are investigated to elucidate the degradation mechanism of MB within 30 min of irradiation. This study is promising towards developing defect mediated and time-efficient photocatalysts for environmental remediation.

Prickly pear fruit extract as photosensitizer for dye-sensitized solar cell.

In this study, we have explored prickly pear fruit extract as a photosensitizer in dye-sensitized solar cells (DSSC). The photosensitizer was isolated from prickly pear fruits by extraction method using ethanol as solvent. Structural, morphological and optical properties of prickly pear extract characterized by XRD, SEM, UV-VIS-DRS, FTIR spectra, respectively. UV-VIS absorption and FTIR spectra of prickly pear fruit extract confirm the presence of betacyanin and hydroxyl groups anchoring onto the TiO2 surface. The absorption maxima at 534 nm in the visible region is prominent. The presence of betacyanin in the extract is indicative that the dye will be useful as a sensitizer in DSSC. Reflectance edge of TiO2 is red-shifted upon the adsorption of natural dye. The XPS analysis showed the charge state of hydroxyl (O-H) groups that are attached with the natural dye adsorbed onto the surface of TiO2. The fabricated DSSC had a conversion efficiency (ɳ) of 0.56% with highest fill factor (FF) of 0.85, open-circuit voltage (Voc) of 0.56 V and short circuit-current density (Jsc) with 1.17 mA/cm2. The value obtained for the fill factor is promising to further explore the prickly pear extract for applicability in DSSC by improving the efficiency.

Study of stainless steel electrodes after electrochemical analysis in sea water condition.

For water electrolysis, a rare earth material (eg., platinum) is often used as an electrode, but because of the high cost and toxicity of chemicals, researchers are searching for cost effective and eco-friendly alternative materials. Various alloys and metals have been long explored for use as electrode materials in different media. Stainless steel (SS 304) electrodes are cost effective and have a large surface area; further their catalytic performance is comparable to that of carbon coated noble metals cathodes. Stainless steel has good mechanical properties and durability so it is widely used in desalination plants, oil and gas industries, ship building, etc. However, over a period of time it corrodes very quickly in saline water. To improve the stability and durability of the electrodes (i.e., to minimize corrosion), we anneal the samples under two different sets of conditions and test the electrodes in 3.5% NaCl solution. The anodic peak (-0.25 V) observed for bare stainless steel result from the formation of iron (II) hydroxide [Fe(OH)2]. The Raman bands observed at 210 and 274 cm-1 for bare stainless steel result from the formation of α-Fe2O3 owing to partial, anodic, and cathodic reactions occurring on the electrode which disrupts the surface layers. High intensity X-ray diffraction (XRD) and Raman peaks of Cr2O3 and MnCr2O4 observed in argon and hydrogen annealed sample after cyclic voltammetry reveal that this sample is more stable than bare and air annealed samples. XRD reveals mixed oxide phases in addition to eskolaite and magnetite phases. Scanning electron microscope (SEM) images show that although the air-annealed sample has a soft, spongy structure, Na and Cl ions are adsorbed in the voids on the outer surface of the electrode leading to quick degradation. For the air-annealed sample the oxide appears to adhere poorly to the stainless steel. Oxygen (ie., oxide composition) may play a key role in adherence and growth of Cr2O3 formed at high temperature. X-ray photoelectron spectroscopy (XPS) reveals that large amounts of Cr and Mn are dissolved/corroded into the electrolyte for air annealed sample which is in good agreement with the Raman and SEM results.

Effect of pH, thermal, electrical and thermomechanical properties of nonlinear optical L-threonine single crystals.

Nonlinear optical L-threonine single crystals have been grown at various pH values. The crystals were subjected to dielectric and thermomechanical measurements at various temperatures. The thermal strength of the grown crystal was also determined by differential scanning calorimetry (DSC) analysis. The results have been discussed in detail.