Thickness-dependent electrochromic properties of solution thermolyzed tungsten oxide thin films

Tungsten oxide (WO₃) thin films are prepared by using a simple and inexpensive solution thermolysis technique. Thin film samples of different thickness are obtained by varying quantity of ammonium tungstate solution sprayed onto the preheated conducting glass substrate. A simple three-electrode cell has been formed to study the electrochemical and electrochromic properties. The electrochemical parameters of the cell such as anodic peak current, anodic peak potential, threshold voltage, amount of H⁺ ions intercalated into and deintercalated out of the WO₃ samples are calculated. The effect of film thickness on these parameters are studied. The extent of electrochromism and reversibility of the colouration/bleaching processes of various WO₃ samples are described. The colouration efficiencies at 633 nm are calculated. The maximum colouration efficiency obtained for thicker film, is 56 cm²/C. The samples were found to be stable in 0.05N H₂SO₄ electrolyte up to 1×10³ colour/bleach cycles.     

Systemic exposure of Paracetamol (acetaminophen) was enhanced by quercetin and chrysin co-administration in Wistar rats and in vitro model: risk of liver toxicity

Intestinal P-glycoprotein (P-gp) and drug-metabolizing enzymes (DMEs) play an important role in the first-pass-metabolism (FPM) and pharmacokinetics (PK) of majority of drugs. Paracetamol is primarily metabolized by conjugation reactions and a little amount (～15%) undergoes cytochrome P450 (CYP2E1)-mediated oxidative metabolism produces a hepatotoxic metabolite, N-acetyl-p-benzoquinonimine (NAPQI). Quercetin and chrysin are naturally occurring flavonoids, reported as modulators of P-gp and DMEs. Therefore, the objective of this study was to evaluate the effects of quercetin and chrysin on the pharmacokinetics of paracetamol using rats and non-everted gut sacs in vitro. Paracetamol was given orally (100?mg/kg) to rats alone and in combination with quercetin (5, 10 and 20?mg/kg) and chrysin (50, 100 and 200?mg/kg) once daily for 21 consecutive days. Blood samples were collected on the 1st day in single dose pharmacokinetic study (SDS) and on the 21st day in multiple pharmacokinetic studies (MDS). The plasma concentrations of paracetamol were determined by HPLC and PK parameters were calculated by using Kinetica (Version 5.1). The maximum plasma concentration (C_max) and area under the curve (AUC_0–12) of paracetamol was significantly increased by quercetin and chrysin co-administration in SDS and MDS. In non-everted rat gut sac method, the absorption of paracetamol was increased by presence of P-gp inhibitors (verapamil, quinidine and ketoconazole), quercetin and chrysin (50?μg/mL). Our findings suggested that the quercetin and chrysin might be inhibited the P-gp and metabolism of paracetamol; thereby increased the systemic exposure of paracetamol. Further studies are needed to evaluate whether the quercetin or chrysin are involved in the formation of NAPQI by CYP2E1 or not on isolated rat hepatocytes or using cell lines.     

Studies on influence of reflux time on synthesis of nanocrystalline TiO2 prepared by peroxotitanate complex solutions

Aqueous peroxotitanate complex (PTC) precursor was used to obtain phase pure anatase nanocrystaline TiO₂. A wet chemical synthesis route was used in which number of aqueous solutions of PTC was refluxed for different time intervals to study the effect of reflux time on final product. Several characterization techniques were used such as DSC–TGA, XRD, UV–Vis, SEM and TEM. The study revealed that there is a significant influence of reflux time on structural, morphological and optical properties of TiO₂. As reflux time of PTC has been increased, crystallite size found to be increased. Also, surface morphology of TiO₂ nanoparticles changed from ‘hexagonal shape’ to ‘rice like’ shape and further in ‘ellipsoid rod like’ shape. Optical band gap energy and refractive index incurred to be altered with respect to reflux time of PTC. Detailed study of refluxed PTC solutions has been reported for the first time in the literature.     

Single step electrosynthesis of Cu2ZnSnS4 (CZTS) thin films for solar cell application

The Cu₂ZnSnS₄ (CZTS) thin films have been electrodeposited onto the Mo coated and ITO glass substrates, in potentiostatic mode at room temperature. The deposition mechanism of the CZTS thin film has been studied using electrochemical techniques like cyclic voltammetery. For the synthesis of these CZTS films, tri-sodium citrate and tartaric acid were used as complexing agents in precursor solution. The structural, morphological, compositional, and optical properties of the CZTS thin films have been studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), EDAX and optical absorption techniques respectively. These properties are found to be strongly dependent on the post-annealing treatment. The polycrystalline CZTS thin films with kieserite crystal structure have been obtained after annealing as-deposited thin films at 550 in Ar atmosphere for 1 h. The electrosynthesized CZTS film exhibits a quite smooth, uniform and dense topography. EDAX study reveals that the deposited thin films are nearly stoichiometric. The direct band gap energy for the CZTS thin films is found to be about 1.50 eV. The photoelectrochemical (PEC) characterization showed that the annealed CZTS thin films are photoactive.     

Surfactant mediated growth of ZnO nanostructures and their dye sensitized solar cell properties

Single crystalline and highly aligned ZnO nanorods, faceted microrods, nanoneedles and nanotowers were grown onto glass substrates by a facile aqueous chemical method at relatively low temperature (90 °C). Various structure directing agents or organic surfactants such as diaminopropane (DAP), polyacrylic acid (PAA) and polyethylenimine (PEI) were used to modify the surface morphology. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and optical absorption. It was found that, vertically aligned ZnO nanorods formation takes place with preferential orientation along (002) plane. The organic surfactants play an important role in modifying the morphology. The samples were further used to fabricate dye sensitized solar cells. The highest photocurrent (670 μA) and efficiency were observed for the ZnO:PEI sample.     

CFD analysis of flow pattern in the agitated thin film evaporator

Agitated thin film evaporator (ATFE) is widely used in chemical, pharmaceuticals and food industries to concentrate the feed solutions. The flow pattern in ATFE has been analyzed using ANSYS-CFX 10.0 software. The flow phenomenon is simulated using free surface multiphase model considering two continuous phases, water and water vapour. The geometry is created in ANSYS-ICEM-10 with 110,300 tetrahedral nodes. The k–? and Reynolds stress homogeneous turbulence models are used with appropriate boundary conditions. The occurrence of bow wave and its variation with respect to flow rate is studied. A thin film of thickness equal to the clearance between blade tip and inner wall is found to adhere to the inner wall. The bow wave is found to travel helically along the inner wall of the evaporator. The shear rate and kinetic energy dissipation is found to be significant at the clearance between blade and inner wall. These values are 10–50 times more than that observed in rest of the volume.     

PVA-coated miniaturized flexible fiber optic sensor for acetone detection: a prospective study for non-invasive diabetes diagnosis

Diabetes is a complex metabolic disorder that leads to various health complications. Present conventional diagnostic methods of puncturing a finger cause pain, discomfort and measurement procedures often lead to irregular testing. Therefore, there is a need for a simple, painless, and portable technique, which can diagnose diabetes non-invasively and in real-time. Acetone vapor in human exhaled breath is a natural biomarker correlated with some metabolic diseases, like diabetes. Thus in this work, Fabry–Perot Interferometer-based polyvinyl alcohol-coated sensor platform for acetone vapor detection non-invasively at room temperature has been proposed and investigated for the prospective study of diabetic detection. The developed sensor platform of approx. 61 μm cavity length was employed for acetone sensing from 0 to 80 µL/L concentration. The evaluation parameters of the developed sensor like sensitivity, the limit of detection, response and recovery time for the acetone vapor detection at room temperature were observed in the order of 43.9 pm/(µL/L), 0.45 µL/L, 60 s and 10 s, respectively. The cross-sensitivity of the sensor was checked with methanol and ethanol. The experimentally observed sensitivity response (swelling) was found in agreement with the theoretically calculated miscibility values obtained from the Hansen solubility parameter model. The thermal stability of the developed sensor was also studied and found linear between the temperature ranges of 25–75 °C. The proposed sensor is simple, miniaturized, flexible, cost-effective, and highly sensitive for low acetone vapor concentration detection at room temperature. Therefore, this sensor maybe explore for diagnosis of diabetes non-invasively via acetone detection from the exhaled breath.

     

Spherical crystallization of celecoxib

Celecoxib exhibits poor flow properties and compressibility. Spherical crystallization of celecoxib was carried out using the solvent change method. An acetone:dichloromethane (DCM):water system was used where DCM acted as a bridging liquid and acetone and water as good and bad solvent, respectively. Hydroxypropylmethylcellulose (HPMC) was used to impart strength and sphericity to the agglomerates. The effect of amount of bridging liquid and speed of agitation was studied using 3² factorial design. Primary properties of the agglomerates were evaluated by infrared spectroscopy, powder X-ray diffraction, and differential scanning calorimetry. The effect of variables on micromeritic, mechanical, compressional, and dissolution behavior was evaluated by response surface methodology. Particle size, bulk density, mean yield pressure (MYP), and drug release were found to be significantly affected by either of the two variables. Interaction of variables significantly affected the MYP.     

Probing into the optical and electrical properties of hybrid Zn<Subscript>1−x</Subscript>Co<Subscript>x</Subscript>Se thin films

Probing into the elemental composition, structural, morphological, optical and electrical transport properties of chemically deposited Zn_1?xCo_xSe (0?≤?x?≤?0.275) thin films with a special emphasis given to the Co²⁺-concentration is presented in this paper. Elemental and structural analysis confirmed the successful realization of Co(ZnSe) thin films. Addition of Co²⁺ into ZnSe host lattice caused morphological changes from globule like morphology to the formation of leaf like appearance composing the disc-decked micro-flakes elongated in size. The optical studies done in the range of wavelengths between 350 to 1200 nm showed a slight red shift in the optical spectrum with increased Co²⁺ concentration in the ZnSe matrix. Effect of increased impurity addition is also reflected in the band gap measurements that a decrease in the bandgap, typically from 2.71 to 1.96 eV, is observed for an increase in Co²⁺ concentration from x?=?0–0.275. The other optical parameters namely, refractive index, extinction coefficient, power factor and dielectric constants were determined from these studies and other variations are adequately explained as a special reference to the Co-concentration. The composition dependence of the electrical transport characteristics were studied using the two-probe and Hall measurement techniques. The effect of Co-concentration on the transport characteristics has been studied and mechanism of an electrical conduction is discussed. A continuous increase in an electrical conductivity with n-type conduction has been observed for these samples.     

Evaluation of non-crystalline cellulose as a novel excipient in solid dose products

Objective: The objective of this study was to evaluate non-crystalline cellulose (NCC) as a novel tablet excipient in solid oral dosage forms in comparison with microcrystalline cellulose (MCC) and silicified microcrystalline cellulose (Prosolv®, SMCC).

Significance: MCC, although a widely used tablet excipient, has diasdvantages in terms of its low dilution potential for potent drugs, and sensitivity to lubricant and moisture. SMCC, a modified version of MCC, has improved tablet compression properties. However, SMCC is expensive and also affects the moisture sorption and particle deformation during compression leading to increased tensile strength and tablet hardness. NCC was found to be similar to SMCC in its performance as a tablet excipient and thus can serve as a cheaper alternative to SMCC.

Methods: Scanning electron microscopy (SEM), X-ray diffrectometry (XRD), and differential scanning calorimetry (DSC) analyses were performed on NCC, MCC, and SMCC. Further, out-of-the die Heckel, Kawakita compact densification and stress-strain analyses were performed to evaluate their compaction and compressibility properties. Various compendial and non-compendial tests were performed to to determine the flow properties of materials. Dissolution studies were performed using amlodipine besylate as a marker drug.

Results: It was found that NCC has similar or even better flow properties and compactibility than MCC due to its porous and amorphous structure whereas it had similar properties as SMCC.

Conclusions: Based on the data, it can be concluded that NCC can serve as a cheaper and better alternative to MCC as excipient in solid dosage forms.