Real time spectroscopic ellipsometry of CuInSe2: Growth dynamics,dielectric function,and its dependence on temperature

This Letter reports real time spectroscopic ellipsometry studies of copper indium diselenide (CuInSe₂; CIS). A Volmer‐Weber nucleation process was identified from the measured thickness dynamics, and accurate dielectric functions were obtained in‐situ, avoiding oxidation while correcting for surface roughness. The energy and broadening parameters of the critical points in the dielectric functions obtained versus measurement temperature (including three previously unreported ones) yield a database that is valuable for on‐line materials analysis. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Tuning the Transconductance of Organic Electrochemical Transistors

Organic electrochemical transistors (OECTs) operate at very low voltages, transduce ions into electronic signals, and reach extremely large transconductance values, making them ideally suited for bio-sensing applications. However, despite their promising performance, the dependence of their maximum transconductance on device geometry and applied voltages are not correctly captured by current capacitive device models. Here, current scaling laws are revised in the light of a recently developed 2D device model that adequately accounts for drift and diffusion of ions inside the polymer channel. It is shown that the maximum transconductance of the devices is found at the transition between the depletion and accumulation region of the transistors, which as well provides an explanation for the observed shift of the transconductance peak with geometric dimensions and the drain potential. Overall, the results provide a better understanding of the working mechanisms of OECTs, and facilitate design rules to optimize OECT performance further.     

Rational Approaches for Drug Designing Against Leishmaniasis

Leishmaniasis has been ignored for many years mainly because it plagues remote and poor areas. However, recently, it has drawn attention of several investigators, and active research is going on for antileishmanial drug discovery. The current available drugs have high failure rates and significant side effects. Recently, liposomal preparations of amphotericin B are available and have proved to be a better drug, but they are very expensive. Miltefosine is one of the few orally administered drugs that are effective against Leishmania. However, it has exhibited teratogenicity, hence, should not be administered to pregnant women. Thus, the search for novel and improved antileishmanial drugs continue. A rational approach to design and develop new antileishmanials can be to identify several metabolic and biochemical differences between host and parasite that can be exploited as drug target. Moreover, many natural products also have significant antileishmanial activity and are yet to be exploited. In the current review, we aim to bring together various drug targets of Leishmania, recent development in the field, future prospects, and hope in the area.     

Non‐destructive optical analysis of band gap profile,crystalline phase,and grain size for Cu(In,Ga)Se2 solar cells deposited by 1‐stage, 2‐stage,and 3‐stage co‐evaporation

Cu(In,Ga)Se₂ (CIGS) thin films co‐evaporated by 1‐stage, 2‐stage, and 3‐stage processes have been studied by spectroscopic ellipsometry (SE). The disappearance of a Cu_2‐xSe optical signature, detected by real time SE during multistage CIGS, has enabled precise endpoint control. Band gap energies determined by SE as depth averages show little process variation for fixed [Ga]/([In] + [Ga]) atomic ratio, whereas their broadening parameters decrease with increasing number of stages, identifying successive grain size enhancements. Refined SE analysis has revealed band gap profiling only for 3‐stage CIGS. Solar cells incorporating these absorbers have yielded increased efficiencies in correlation with phase control, grain size, and band gap profiling. Copyright © 2013 John Wiley & Sons, Ltd.     

Biophysical and Folding Parameters of Trypanothione Reductase from <Emphasis Type="Italic">Leishmania infantum</Emphasis>

Out of various tropical diseases caused by trypanosomatids, leishmaniasis is a life-threatening disease caused by the leishmania parasite. We are targeting the thiol metabolic pathway of the parasite for drug development, and trypanothione reductase (TryR) is a key enzyme of this pathway. It is important to gather significant knowledge about biophysical and intrinsic properties of this enzyme which will be helpful in better understanding of this drug-target enzyme. We report here the modulation of activity and stability of TryR from Leishmania infantum in the presence of various denaturants and pHs. The enzyme is quite stable under high concentration of denaturants and showed better stability compared to TryR of Leishmania donovani, whose sequence differs at only on position (Ala363→Gly). Structural basis of the destabilizing effects is discussed.     

Determination of aluminium and gallium: Chelate formation of trivalent aluminium and gallium with eriochrome cyanine RC

Summary ECRC forms violet coloured chelates with aluminium(III) and gallium(III) with _max 540 nm and 550 nm respectively at p_H 4.5 and 3.5. The metal ligand ratio in both the cases has been found to be 11. The chelates of aluminium and gallium are stable between p_H 3.5 to 5.5 and p_H 2.7 to 6.0 respectively. The apparent stability constants are 10^4.9 (p_H 4.5) and 10^4.8 (p_H 3.8) respectively for the aluminium and gallium chelates at 25°. The range of concentration for adherence toBeer's law, the effective range of photometric determination and the molar absorptivities are 0.27 to 0.97 p. p. m.; 0.18 to 0.97 p. p. m. and 3.20 · 10⁴ for aluminium, and 0.093 to 2.52 p. p. m.; 0.46 to 2.52 p. p. m. and 2.20 ·10⁴ for gallium respectively.

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Zusammenfassung Eryochromcyanin RC bildet mit Al(III) und Ga(III) violett gefärbte Chelate, die bei p_H 4,5 bzw. 3,5 Absorptionsmaxima bei 540 bzw. 550 run haben. In beiden Fällen ist das Verhältnis Metall: Ligand=11. Die Chelate sind zwischen p_H 3,5 und 5,5 bzw. zwischen p_H 2,7 und 6,0 stabil. Die entsprechenden Konstanten lauten 10^4,9 (p_H 4,5) bzw. 10^4,8 (p_H 3,8) bei 25°. Bei Al liegt der Gültigkeitsbereich für das Beersche Gesetz zwischen 0,27 und 0,97 ppm; für die photometrische Bestimmung zwischen 0,18 und 0,97 ppm. Die molare Extinktion beträgt 3,20 · 10⁴. Die entsprechenden Werte für Gallium lauten: 0,093 bis 2,52 ppm; 0,46 bis 2,52 ppm und 2,20 · 10⁴.

     

Open tubular supercritical fluid chromatography of triterpene acids from Dysoxylum pettigrewianum (Meliaceae)

Open tubular supercritical fluid chromatography (SFC) with carben dioxide as the mobile phase has been investigated for the separation of four triterpene acids, two of which were structural isomers. These compounds, isolated from Dysoxylum pettigrewianum (Meliaceae), were chromatographed on three stationary phases with different selectivities. 30%-biphenylmethylpolysiloxane and polyethylene glycol (Carbowax 20M) phases exhibited poor chromatographic selectivity for the compounds. The separation was improved by employing the shape selectivity of a liquid crystalline biphenylcarboxylate ester polysiloxane and utilizing simultaneous temperature and pressure programming. The elution order was explained on the basis of the molecular structures of the triterpene acids, and their interaction with the liquid crystal phase.     

Development of Green Waterborne UV-Curable Castor Oil-Based Urethane Acrylate Coatings: Preparation and Property Analysis

A series of novel waterborne UV-curable polyurethane dispersions were synthesized from castor oil, IPDI, DMPA, and HEMA by the acetone process. The prepared UV-PUD was mixed with three different monomers and characterized for the parameters relevant to the study by physical, spectroscopic, and chemical methods. The effect of monomer type on the physicochemical and thermal properties of UV-PUDs revealed that the number of unsaturated groups present in the monomer had a pronounced effect on physicochemical, mechanical, and thermal properties. The combination of renewable resource and environmentally compliant technology give these UV-PUDs potential scope in coating applications.     

Effect of processing on dielectric properties of (0.95)PbZr0.52Ti0.48O3–(0.05)BiFeO3

An effort has been made to synthesize solid solution of a composition with x=0.05 in the system (1?x)PbZr_0.52Ti_0.48O₃–(x)BiFeO₃ by the sol–gel method. XRD patterns of the pure PZT and BFO modified PZT samples have shown single phase formation. The effects of substitution of BFO on dielectric properties of PZT have been studied in the frequency range 10 Hz to 100 kHz and temperature range from RT to 773 K. The density was optimized by sintering the BFO modified PZT samples at different temperatures in four batches, S1, S2, S3 and S4. P–E hysteresis loop measurements for all the samples have shown almost saturated polarization. It has been observed that sample S2, sintered at 950 °C, exhibits superior dielectric properties of the four samples. The occurrence of weak ferromagnetism, observed in the M–H hysteresis loop, indicates coupling between ferroelectricity and magnetism. Impedance analysis has revealed that all the samples, sintered at different temperatures, have a different grain resistance. A large change in ac conductivity around T _c has been observed in all the samples.