Thermo and photoluminescence properties of Eu activated hexagonal, monoclinic and cubic gadolinium oxide nanorods

Different phases of Eu³⁺ activated gadolinium oxide (Gd (OH)₃, GdOOH and Gd₂O₃) nanorods have been prepared by the hydrothermal method with and without cityl trimethyl ammonium bromide (CTAB) surfactant. Cubic Gd₂O₃:Eu (8 mol%) red phosphor has been prepared by the dehydration of corresponding hydroxide Gd(OH)₃:Eu after calcinations at 350 and 600 °C for 3 h, respectively. When Eu³⁺ ions were introduced into Gd(OH)₃, lattice sites which replace the original Gd³⁺ ions, a strong red emission centered at 613 nm has been observed upon UV illumination, due to the intrinsic Eu³⁺ transition between ⁵D₀ and ⁷F configurations. Thermoluminescence glow curves of Gd (OH)₃: Eu and Gd₂O₃:Eu phosphors have been recorded by irradiating with gamma source (⁶⁰CO) in the dose range 10-60 Gy at a heating rate of 6.7 °C sec⁻¹. Well resolved glow peaks in the range 42-45, 67-76, 95-103 and 102-125 °C were observed. When γ-irradiation dose increased to 40 Gy, the glow peaks were reduced and with increase in γ-dose (50 and 60 Gy) results the shift in first two glow peak temperatures at about 20 °C and a new shouldered peak at 86 °C was observed. It is observed that there is a shift in glow peak temperatures and variation in intensity, which is mainly attributed to different phases of gadolinium oxide. The trapping parameters namely activation energy (E), order of kinetics (b) and frequency factor were calculated using peak shape and the results are discussed.     

Effect of dibutyl phthalate as plasticizer on high-molecular weight poly(vinyl chloride)–lithium tetraborate-based solid polymer electrolytes

A series of different composition of polymer electrolytes-based on poly(vinyl chloride) (PVC) as host polymer, lithium tetraborate (Li₂B₄O₇) as dopant salt, and dibutyl phthalate (DBP) as plasticizer were prepared by solution casting method. The interaction between the PVC, Li₂B₄O₇, and DBP were studied by Fourier transform infrared. The shifting, broadening, and splitting of transmission peaks were the evidences of complexation. The highest ionic conductivity polymer electrolyte of 2.83 × 10⁻⁶ S/cm was achieved at ambient temperature upon addition of 30 wt.% of DBP. In addition, the temperature-dependent conductivity, frequency-dependent conductivity, dielectric permittivity, and modulus studies were performed. The temperature-dependent conductivity of the polymer electrolytes was found to obey the Arrhenius behavior. The thermal stability of polymer electrolytes was verified by thermogravimetric analysis. The lower in glass transition temperature was proven in differential scanning calorimetry, whereas the higher amorphous region within the polymer matrix was demonstrated in X-ray diffraction.     

Investigation of dibutyl phthalate as plasticizer on poly(methyl methacrylate)–lithium tetraborate based polymer electrolytes

Polymer electrolyte membranes, comprising of poly(methyl methacrylate) (PMMA), lithium tetraborate (Li₂B₄O₇) as salt and dibutyl phthalate (DBP) as plasticizer were prepared using a solution casting method. The incorporation of DBP enhanced the ionic conductivity of the polymer electrolyte. The polymer electrolyte containing 70 wt.% of poly(methyl methacrylate)–lithium tetraborate and 30 wt.% of DBP presents the highest ionic conductivity of 1.58 × 10⁻⁷ S/cm. The temperature dependence of ionic conductivity study showed that these polymer electrolytes obey Vogel–Tamman–Fulcher (VTF) type behaviour. Thermogravimetric analysis (TGA) was employed to analyse the thermal stability of the polymer electrolytes. Fourier transform infrared (FTIR) studies confirmed the complexation between poly(methyl methacrylate), lithium tetraborate and DBP.     

Optical and hydrophobic properties of co-sputtered chromium and titanium oxynitride films

The chromium and titanium oxynitride films on glass substrate were deposited by using reactive RF magnetron sputtering in the present work. The structural and optical properties of the chromium and titanium oxynitride films as a function of power variations are investigated. The chromium oxynitride films are crystalline even at low power of Cr target (≥60 W) but the titanium oxynitride films are amorphous at low target power of Ti target (≤90 W) as observed from glancing incidence X-ray diffraction (GIXRD) patterns. The residual stress and strain of the chromium oxynitride films are calculated by sin² ψ method, as the average crystallite size decreases with the increase in sputtering power of the Cr target, higher stress and strain values are observed. The chromium oxynitride films changes from hydrophilic to hydrophobic with the increase of contact angle value from 86.4° to 94.1°, but the deposited titanium oxynitride films are hydrophilic as observed from contact angle measurements. The changes in surface energy were calculated using contact angle measurements to substantiate the hydrophobic properties of the films. UV-vis and NIR spectrophotometer were used to obtain the transmission and absorption spectra, and the later was used for determining band gap values of the films, respectively. The refractive index of chromium and titanium oxynitride films increases with film packing density due to formation of crystalline chromium and titanium oxynitride films with the gradual rise in deposition rate as a result of increase in target powers.     

Almost Ricci solitons and K-contact geometry

We give a short Lie-derivative theoretic proof of the following recent result of Barros et al. “A compact non-trivial almost Ricci soliton with constant scalar curvature is gradient, and isometric to a Euclidean sphere”. Next, we obtain the result: a complete almost Ricci soliton whose metric \(g\) is \(K\) -contact and flow vector field \(X\) is contact, becomes a Ricci soliton with constant scalar curvature. In particular, for \(X\) strict, \(g\) becomes compact Sasakian Einstein.     

Almost Contact Lagrangian Submanifolds of Nearly Kaehler 6-Sphere

For a Lagrangian submanifold M of S ⁶ with nearly Kaehler structure, we provide conditions for a canonically induced almost contact metric structure on M by a unit vector field, to be Sasakian. Assuming M contact metric, we show that it is Sasakian if and only if the second fundamental form annihilates the Reeb vector field ξ, furthermore, if the Sasakian submanifold M is parallel along ξ, then it is the totally geodesic 3-sphere. We conclude with a condition that reduces the normal canonical almost contact metric structure on M to Sasakian or cosymplectic structure.     

Inhibitive properties of a phosphonate-based formulation for corrosion control of carbon steel

The aim of the present work was to study the corrosion inhibition of carbon steel using a ternary formulation. This new ternary inhibitor formulation, viz., 2-phosphonobutane-1,2,4-tricarboxylic acid (PBTC), with zinc ions and silicate ions was used to protect carbon steel from corrosion in a low-chloride environment. The gravimetric studies showed that 96 % inhibition efficiency was achieved with the ternary system consisting of 50 ppm PBTC, 50 ppm Zn²⁺ ions, and 10 ppm silicate ions. Out of 0.310 mmol of Zn²⁺ ions, 0.218 mmol was diffused from the bulk of the solution to the metal surface, as revealed from the studies of the solutions by atomic absorption spectroscopy (AAS). Electrochemical methods (potentiostatic polarization and electrochemical impedance spectroscopy) and surface characterization techniques [Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), and atomic force microscopy (AFM)] were used to ascertain the nature of the protective film and for explaining the mechanistic aspects of corrosion inhibition.     

A highly sensitive LC‐MS/MS method for the determination of S‐citalopram in rat plasma: application to a pharmacokinetic study in rats

A highly sensitive, rapid assay method has been developed and validated for the estimation of S‐citalopram (S‐CPM) in rat plasma with liquid chromatography coupled to tandem mass spectrometry with electrospray ionization in the positive‐ion mode. The assay procedure involves a simple liquid–liquid extraction of S‐CPM and phenacetin (internal standard, IS) from rat plasma with t‐butyl methyl ether. Chromatographic separation was operated with 0.2% formic acid:acetonitrile (20:80, v/v) at a flow rate of 0.50 mL/min on a Symmetry Shield RP₁₈ column with a total run time of 3.0 min. The MS/MS ion transitions monitored were 325.26 → 109.10 for S‐CPM and 180.10 → 110.10 for IS. Method validation and pre‐clinical sample analysis were performed as per FDA guidelines and the results met the acceptance criteria. The lower limit of quantitation achieved was 0.5 ng/mL and the linearity was observed from 0.5 to 5000 ng/mL. The intra‐ and inter‐day precisions were in the range of 1.14–5.56 and 0.25–12.3%, respectively. This novel method has been applied to a pharmacokinetic study and to estimate brain‐to‐plasma ratio of S‐CPM in rats. Copyright © 2010 John Wiley & Sons, Ltd.