Role of PVA in synthesis of nano Co3O4‐decorated graphene oxide

Polymeric materials have been found to be ideal candidates for the synthesis of organic–inorganic nanomaterials. We have obtained Co₃O₄‐decorated graphene oxide (GO) nanocomposites by a simple polymer combustion method. Polyvinyl alcohol (PVA) of two different molecular weights, 14,000 and 125,000, was used for the synthesis. The pristine sample was annealed at 300, 500, and 800°C. PVA has played an important role in the formation of GO and Co₃O₄ nanoparticles. Synthesized Co₃O₄–GO nanocomposites were characterized by X‐ray diffraction, Fourier transform infrared, Raman, electron paramagnetic resonance, transmission electron microscopy, and vibrating sample magnetometry. Reflection peaks at 12° and 37° in an X‐ray study confirm the formation of Co₃O₄–GO. Raman study validates the presence of GO in nanocomposites of Co₃O₄–GO. Room temperature ferromagnetism was observed in all annealed samples. The highest coercivity of 462 G was observed for 300°C annealed samples as compared with bulk Co₃O₄. On the basis of the results obtained, a mechanism of formation is proposed. Copyright © 2015 John Wiley & Sons, Ltd.     

Calotropis procera extract induces apoptosis and cell cycle arrest at G2/M phase in human skin melanoma (SK-MEL-2) cells

Calotropis procera (family: Asclepiadaceae) contains cardiac glycosides which are cytotoxic to cancer cells. The extracts of C. procera have been reported to be cytotoxic to many cancer cell lines and this is the first report against the human skin melanoma cells (SK-MEL-2). The SK-MEL-2 cells treated with C. procera methanolic extract (CPME) were analysed for growth inhibition and apoptosis. The exposure of phosphatidylserine in apoptotic SK-MEL-2 was analysed by using the Annexin-V FITC flow cytometry method. In CPME-treated SK-MEL-2 cells, 19.6% of apoptotic and 58.3% dead cells were observed. The 15.97% and 15.85% of early apoptotic cells were found at 20 μg/mL of the ouabain and paclitaxel, respectively. Active caspases, nuclear degradation confirmed apoptotic SK-MEL-2 cells in time- and dose-dependent manner. The cell cycle analysis shows that CPME treated cells halt at G2/M phase. Significant cytotoxic activity of CPME against SK-MEL-2 may be attributed to its high cardenolide content.     

Quantitative surface-enhanced Raman measurements with embedded internal reference

Analytical applications of SERS are often more associated with qualitative than quantitative analysis, because of the difficulty in obtaining quantitative SERS results. In this paper we introduce a new strategy to quantitatively measure the SERS signals of analytes based on Au-core/Ag-shell nanoparticles with embedded 4-aminothiophenol as the internal reference. Successful detections of two analytes, Toluidine Blue O in aqueous solution (detection limit of 0.1 μM) and melamine in milk (detection limit of ∼5 μM), are demonstrated. The improvement in the linear fitting illustrates that the use of internal reference significantly improves the accuracy of the quantitative SERS measurements. The successful detection of melamine in milk illustrates the versatility of this detection scheme for a wide variety of analytes.     

Comparative study on the photocatalytic properties of Ag3PO4 fabricated by different methods

Research on Chemical Intermediates - A comparative study was carried out on the photocatalytic properties depending on Jodifferent morphologies of Ag3PO4 fabricated by different methods, i.e. as...     

Torsional oscillations of an infinite plate in an elastico-viscous fluid

Summary The equations of motion of an infinite plate performing torsional oscillations in Walters elastico-viscous liquid B have been solved by expanding the velocity profile in powers of the amplitude of oscillation of the plate. The first order solution consists of a transverse velocity and the second-order solution gives a radial-axial flow composed of a steady part and a fluctuating part. The steady part of the radial flow does not vanish outside the boundary layer and hence the equations are solved by another approximate method for the steady part of the flow. The effects of the non-Newtonian term is to increase the non-dimensional boundary layer to start with and subsequently to decrease it and to increase the shearing stress at the plate. The steady radial and the steady axial velocities fall short of the inelastic flow in the beginning but later on their values lie above.     

Optical and photocatalytic properties of single crystalline ZnO at the air-liquid interface by an aminolytic reaction

Crystalline flowerlike ZnO was synthesized by an aminolytic reaction at the air-liquid interface in an aqueous media at an alkaline pH. A thin visible film was formed at the air-liquid interface by self-assembly of flowerlike ZnO. Diffraction studies show rearrangement of the single crystalline units at the air-liquid interface leading to the formation of nanobelts. These nanobelts overlap systematically to form petals of the flowerlike structure; individual petals get curved with time. Each nanobelt is found to be single crystalline and can be indexed as the hexagonal ZnO phase. The organic product formed in the aminolytic reaction and dissolution-reprecipitation mechanism is the driving force for the formation of flowerlike ZnO at the air-liquid interface. A clear relationship between the surface, photocatalytic, and photoluminescent properties of ZnO is observed. The flowerlike structure exhibits a blue shift (3.56 eV) in the band emission as compared to bulk ZnO (3.37 eV). The photodegradation of methylene blue over the flowerlike ZnO catalyst formed at the air-liquid interface and in the sediments shows enhanced photocatalytic activity. The sub-bands formed due to surface defects facilitate separation of charge carriers increasing their lifetime, leading to enhanced photocatalytic activity of flowerlike ZnO.     

Interface-induced anisotropy and the nematic glass/gel state in jammed aqueous Laponite suspensions

Aqueous suspensions of Laponite, a system composed of disklike nanoparticles, are found to develop optical birefringence over several days, well after the suspensions solidified because of jamming. The optical anisotropy is particularly enhanced near the air-Laponite suspension interface over length scales of several millimeters, which is beyond 5 orders of magnitude larger than the particle length scale, suggestive of large-scale ordering influenced by the interface. The orientational order increases with time and is always greater for higher concentration of salt, higher concentration of Laponite, and higher temperatures of the suspension. Although weakly birefringent, Laponite suspensions covered by paraffin oil do not show any enhancement in optical anisotropy near the interface compared to that in the bulk. We suggest that the expedited structure formation near the air interface propagating progressively inside the sample is responsible for the observed behavior. We discuss the observed nematic ordering in the context of glass-like and gel-like microstructure associated with aqueous Laponite suspensions.     

Improvement of some pharmaceutical properties of mycophenolate mofetil (MMF) by para sulphonatocalix[4]resorcinarene inclusion complex

As a part of our investigations to unfold the chemistry of calixresorcinarene, we have focused on the formation of inclusion complex of a poorly soluble (43 μg ml^?1 at pH 7) drug mycophenolate mofetil (MMF) an immunosuppressive agent and an inosine monophosphate dehydrogenase (IMPDH) inhibitor with para sulphonatocalix[4]resorcinarene (PSC4R). The complete complexation of the drug was achieved after 48 h of stirring with para sulphonatocalix[4]resorcinarene(PSC[4]R) in water and evaporation of water yield the solid complex. The interaction between para sulphonatocalix[4]resorcinarene(PSC[4]R) and MMF in solid state inclusion complexes was accomplished by aqueous phase solubility studies, Thermal Analysis, HPLC, PXRD, FT-IR, and UV–Vis spectroscopy. The results of the phase solubility experiments are in good conformity to signify the formation of 2:1 PSC4R: MMF complexes. The purpose of this study was to enhance solubility and resulting in high dissolution rate and bioavailability of this essentially water insoluble drug. The results of the in vivo study shows that there is a remarkable change in the toxicity of the pure drug MMF and complex did not produce any mortality up to 2200 mg kg^?1.     

Oxide thickness and roughness factor as parameters for TiO<Subscript>2</Subscript>-dye sensitized solar cells performance

Oxide surface roughness in connection to oxide thickness has proved to be a key parameter for the performance of a dye sensitised solar cell. In this work, the numerical simulation of the system TiO₂-photo sensitive dye of a dye sensitized TiO₂ solar cell focuses on these two parameters. The steady-state numerical model used is based on the continuity and transport equations for charge species involved in the system, in connection to Poisson’s equation. Light absorbance is set dependent upon TiO₂ porosity and resulting electron density after illumination is derived as a function of the illuminating beam characteristics and material properties. Electron lifetime in the bulk is set dependent upon electron distribution with electron lifetime at the surface taking into consideration surface recombination. An effective dielectric constant dependent also upon the porosity of TiO₂ is used in the model. Results for different values of the TiO₂ thickness and surface roughness leading to optimum values for the cell performance are found in accordance with results reported in the literature.     

Effect of formic acid addition on water cluster stability and structure

Computational chemistry simulations were performed to determine the effect that the addition of a single formic acid molecule has on the structure and stability of protonated water clusters. Previous experimental studies showed that addition of formic acid to protonated pure water results in higher intensities of large-sized clusters when compared to pure water and methanol-water mixed clusters. For larger, protonated clusters, molecular dynamics simulations were performed on H(+)(H(2)O)(n), H(+)(H(2)O)(n)CH(3)OH, and H(+)(H(2)O)(n)CHOOH clusters, 19-28 molecules in size, using a reactive force field (ReaxFF). Based on these computations, formic acid-water clusters were found to have significantly higher binding energies per molecule. Addition of formic acid to a water cluster was found to alter the structure of the hydrogen-bonding network, creating selective sites within the cluster, enabling the formation of new hydrogen bonds, and increasing both the stability of the cluster and its rate of growth.