a-Si/SiN<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> multilayered light absorber for solar cell

40 alternate a-Si/SiN _x multilayer are incorporated as an absorber layer in a p–i–n solar cell. The device is fabricated using hot-wire chemical vapor deposition (HWCVD) technique. The structure of the multilayer film is examined by high resolution transmission electron microscopy (HR-TEM) which shows distinct formation of alternate a-Si and SiN _x layers. The a-Si and SiN _x layers have thickness of ~3.5 and 4 nm, respectively. The photoluminescence (PL) of multilayer film shows bandgap energy of ~2.52 eV, is larger than that of the c-Si and a-Si. Dark and illuminated current–voltage (I–V) characterization of the ML films shows that these ML are photosensitive. In the present work, it is seen that the p–i–n structure with i-layer as ML quantum well (QW) structures show photovoltaic effect with relatively high open-circuit voltage (V _OC). The increment of bandgap energy in PL and high V _OC of the device is attributed to the quantum confinement effect (QCE).     

Quartz tuning fork based portable sensor for vapor phase detection of methanol adulteration of ethanol by using aniline-doped polystyrene microwires

The authors describe a sensor capable of detecting methanol adulteration of ethanol. The sensor is based on the use of quartz tuning forks (QTFs) that were functionalized with polymer wires made from a combination of polystyrene (PS) and aniline. Exposure to organic vapors causes the resonance frequency of the functionalized QTF to change, and this can be used to identify the type and concentration of the analyte. A mixture of methanol and ethanol vapors in varying concentrations was exposed to the QTF polymer system. The resulting shift in the resonance frequency of the QTF was firstly used to determine the concentration of alcohol vapor, which is reflected in the amount of shift. Secondly, the nature of change in resonance frequency was used to determine the type of alcohol exposed to the sensor. The sensitivity and selectivity of the sensors to ethanol and methanol vapors has been investigated. A portable hand-held prototype sensor has been developed which displays the percentage of two alcohols it is exposed to. It can detect ethanol adulteration where the methanol concentration is as low as 5%.

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Graphical abstract Spring loaded Quartz Tuning Fork sensors functionalized with polystyrene-aniline wires exhibit opposite responses (increase and decrease in frequency) to vapors of ethanol and methanol respectively.The methanol adulteration of ethanol solutions may thus be detected by sensing their vapors.

     

Comparison of transfer factors of <Superscript>137</Superscript>Cs from soil to leafy vegetables in pot experiment and ambient environment

The paper deals with the transfer factors (TF) generated for a few varieties of leafy vegetables (spinach, fenugreek, and amaranths) consumed by the locals around Tarapur atomic power station environment in India. The soil and leafy vegetable samples collected from the ambient environment of nuclear site were used for the determination of the TFs and they were compared with TFs generated from pot experiments under controlled conditions for ¹³⁷Cs. The activity of ¹³⁷Cs in soil and each vegetable was determined by gamma spectrometry using HPGe detector (35 and 160% relative efficiency) and was reported on dry weight basis for both ambient environment and pot samples. The radioactive effluent containing ¹³⁷Cs (pH ~7) from nuclear power station was used to spike the soil for pot (size 90 cm × 45 cm × 42 cm) experiment. The TFs obtained for ambient environment and pot experiment were found to be in the range of 0.035–0.592 and 0.0054–0.29, respectively. It is observed that TFs of ambient environment are in good agreement with those obtained in the pot experiment conducted under controlled conditions. Further, the observed TF values at Tarapur nuclear site are comparable with the range of typical IAEA transfer factor values for general leafy vegetation (0.11–2.9) for tropical environment.     

A Simple and Sensitive HPTLC Method for Quantitative Analysis of Darunavir Ethanolate Tablets

JPC – Journal of Planar Chromatography – Modern TLC - A quantitative high-performance thin-layer chromatography (HPTLC) method for determination of darunavir ethanolate (DRV) in tablets...     

Review of Synthesis of 1,3,4-Oxadiazole Derivatives

1,3,4-Oxadiazole nucleus shows a broad spectrum of pharmaceutical applications. Thus, in recent years scientists have developed various new methods for the synthesis of its derivatives. Here we give a review of recent developments in the synthesis over the past decade (2004–2013).     

Sphere‐to‐Rod Transitions in Cationic Micelles: Quaternary Ammonium Halides+Phenol+Water Systems

Viscosity measurements on aqueous micellar solutions of cationic surfactants containing phenol with and without sodium bromide were made to study the sphere‐to‐rod transitions. Effect of surfactant structure (nonpolar tail, polar head group sizes and counterion), temperature, and phenol and sodium bromide concentration on the viscosity behavior of the surfactant solution is discussed. The sphere‐to‐rod transition is usually indicated by a marked increase in viscosity. While low temperature, high surfactant concentration, presence of salt, and hydrophobic nature of surfactant all favor the formation of rod‐like micelles, the presence of phenol showed peculiar behavior. Initial additions of phenol (up to about 2.5 wt%) showed a marked increase in viscosity, independent of the nature and concentration of surfactant and temperature; lower viscosities were observed at higher phenol concentration. Conductance and sound velocity results support the viscosity results.     

The synthesis and characterization of calix[4]arene based azo dyes

A series of azocalix[4]arene dyes (1–7) were prepared by linking 2,4-di-chloroaniline, 2,4,5-tri-chloroaniline, 2,4-di-nitroaniline, 2-nitro p-toluidin, 4-nitro o-toluidin, 5-nitro o-toluidin and sulfanilic acid, to calix[4]arene through a diazo-coupling reaction. These compounds were characterized by elemental analysis, FT-IR, ¹H NMR, ¹³C NMR, MALDI-TOF, UV–Vis., DSC, and DTA. The absorption properties of the synthesized dyes were studied and the application of the water soluble dye on cotton and wool was discussed. Solvent based inks were investigated and the fastness properties of formulated inks were also discussed.     

trans-2,5-Disubstituted pyrrolidines: Rapid stereocontrolled access from sulfones

A direct and versatile route for the reliable synthesis of trans-2,5-disubstituted pyrrolidines from pyroglutamic acid is reported, which can be conducted at scale and without chromatographic purification of key intermediates.     

Development and Validation of a Stability Indicating LC Method for the Determination of Faropenem in Pharmaceutical Formulations

A simple, selective and sensitive stability indicating LC method has been developed and validated for the determination of faropenem in bulk drug and pharmaceutical formulations in the presence of degradation products. The separation was achieved by using an isocratic mobile phase mixture of acetate buffer of pH 3.5 and methanol (65:35, v/v) and 250 mm × 4.6 mm I.D., 5 μm particle size SGE make Wakosil C-18 AR column at flow rate of 1.0 mL min^?1 with detection at 305 nm. The retention time of faropenem is 6.63 min and was linear in the range of 5–75 μg mL^?1 (r = 0.9999). The drug was subjected to stress conditions of hydrolysis, oxidation, photolysis and thermal degradation and was found to be unstable in all the stress conditions. The proposed method was successfully employed for quantification of faropenem in bulk drug and its pharmaceutical formulations.