High performing magnesium aluminate-coated separator for lithium batteries

A high performing and thermally stable magnesium aluminate (MgAl₂O₄) coated on both sides of Celgard 2320 for applications in lithium batteries was prepared. The MgAl₂O₄-coated membrane was thermally stable up to 440 °C and capable of up-taking electrolytes up to 250%. The contact angle of MgAl₂O₄-coated membrane was lower (21°) than that of uncoated membrane. The MgAl₂O₄-coated ceramic separator exhibited appreciable ionic conductivity and better compatibility with lithium metal anode. Finally, a 2032-type coin cell comprising Li/MgAl₂O₄-coated separator/LiFePO₄ was assembled and its charge-discharge behavior was analyzed at 0.1, 0.5, and 1 C-rates. A stable discharge capacity was achieved even at 1 C-rate which qualifies this MgAl₂O₄-coated membrane for lithium battery applications.

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Coupling and crosstalk characteristics of hybrid silicon plasmonic waveguides

In this paper, the design and analysis of an ultracompact coupler based on a hybrid silicon plasmonic waveguide (HSPW) is proposed and its coupling and crosstalk characteristics have been theoretically investigated for the development of optical interconnects that can be realized using well-established complementary metal-oxide-semiconductor-compatible fabrication techniques. To determine the minimum horizontal separation distance and efficient coupling length for the designed coupler, the symmetric and antisymmetric supermodes are obtained and their characteristics are studied at a wavelength of 1.55 μm. Efficient light coupling is exhibited by the HSPW coupler with 75 % of power transfer between the two HSPWs with ultrashort coupling length of 2.14 μm when the separation distance is 50 nm. Further, it is shown that the crosstalk is significantly reduced with the insertion of metallic strip between the two HSPWs for realizing highly dense integrated plasmonic circuits.     

Structural and electrical characterization of BiFeO3–NaTaO3 multiferroic

Using a standard high-temperature solid-state reaction technique, polycrystalline samples of (Bi_1?x , Na _x ) (Fe_1?x , Ta _x ) O₃ (x = 0.0, 0.5) were prepared. The formation of the desired materials was confirmed by X-ray diffraction. The surface texture of the prepared materials recorded by scanning electron microscope exhibits a uniform grain distribution with small voids suggesting the formation of high-density pellet samples. The impedance and dielectric properties of the materials were investigated as a function of temperature and frequency. The relative dielectric constant and loss tangent of BiFeO₃ decrease on addition of NaTaO₃ (x = 0.5). The effect of addition of NaTaO₃ on grain and grain boundary contributions in the resistive and capacitive components of BiFeO₃ was studied using complex impedance spectroscopy. The value of activation energy due to both grain and grain boundary of both the samples is nearly same. The nature of variation of dc conductivity confirms the Arrhenius behavior of the materials. Study of frequency dependence of ac conductivity suggests that the materials obey Jonscher’s universal power law and the presence of ionic conductivity.     

Dynamic viscosity versus probe-reported microviscosity of aqueous mixtures of poly(ethylene glycol)

Correlation between the dynamic viscosity (η) and the microviscosity of a hybrid green medium constituted of water and poly(ethylene glycol) (PEG) of average molar mass (200, 400, and 600) g · mol^?1, respectively, is explored over the temperatures range (10 to 90) °C across the complete composition regime. The microviscosity is obtained using a fluorescence probe 1,3-bis-(1-pyrenyl)propane (BPP), which is manifested through the ratio of the monomer-to-intramolecular excimer intensities (I_M/I_E). Aqueous PEG mixtures are observed to behave similar to Newtonian fluids as the temperature dependence of dynamic viscosity follows Arrhenius-type behavior. Surprisingly, a simple and convenient linear dependence of ln η with wt% PEG of the mixture is established. The BPP I_M/I_E is observed, in general, to increase with the bulk dynamic viscosity of the mixture having >10 wt% PEG suggesting a good correlation between the bulk dynamic viscosity and BPP-reported microviscosity when the viscosity of the aqueous PEG mixture is relatively high.     

Recent advancement in the synthesis of phenoxazine derivatives and their analogues

In recent years, angular and linear phenoxazines and their derivatives and polymers have attracted much attention due to their great pharmacological and industrial utility. So it becomes imperative to review the work done in this area more frequently. Therefore, various synthetic routes for phenoxazines are reviewed here comprehensively.     

Optical,thermal and microstructural studies of epoxy-CoSO4.7H2O hybrid material

Organic–inorganic polymer hybrid films of epoxy polymer were prepared, using Cobaltous sulfate heptahydrate (CoSO₄.7H₂O) as a filler component, by physical blending method. UV–Vis optical absorption spectra were analyzed to determine optical band gaps (E_g) of the hybrid material. FTIR studies revealed the interaction of inorganic component with molecules of the polymer matrix. Glass transition temperature (T_g) and degradation temperature were determined by DSC. TG analysis showed the improvement in thermal stability of prepared hybrid films. XRD patterns revealed the amorphous nature of the pure epoxy polymer. Additional sharp peaks were seen for higher filler levels (FLs), indicating self formed nanostructures in the material, which was also evident from SEM analysis.     

Ab initio quantum chemical investigation of the ground and excited states of salicylic acid dimer

The structure and stability of different forms of salicylic acid dimer have been examined by Hartree-Fock and density functional theoretic calculations using 6-31G(d,p) and 6-311++g(d,p) basis sets. Vertical excitation energies for the monomer as well as the dimer have been computed using the time-dependent density functional theory using 6-311++G(d,p) basis set. The predicted absorption maxima for the first excited singlet state of salicylic acid monomer and the dimer of the primary form are in reasonable agreement with the experimental result. There is a slight red shift (approximately 6 nm) in the absorption maximum in going from the monomer to the dimer, in accord with the experimental observation. Configuration-interaction calculations including single excitation have been carried out to map the potential-energy profile for the intra- as well as the intermolecular proton transfer in different forms of the dimer. The barrier for proton transfer in the ground state as well as the excited states makes it clear that most of the processes take place in the primary form and largely by intramolecular proton transfer.     

Stability indicating high-performance thin-layer chromatographic determination of gatifloxacin as bulk drug and from polymeric nanoparticles

A simple, sensitive, selective, precise and stability indicating high-performance thin-layer chromatographic method for determination of gatifloxacin both as a bulk drug and from polymeric nanoparticles was developed and validated as per the International Conference on Harmonization (ICH) guidelines. The method employed thin-layer chromatography (TLC) aluminium plates precoated with silica gel 60F-254 as the stationary phase and the mobile phase consisted of n-propanol-methanol-concentrated ammonia solution (25%) (5:1:0.9, v/v/v). This solvent system was found to give compact spots for gatifloxacin (R_f value of 0.60 ± 0.02). Densitometric analysis of gatifloxacin was carried out in the absorbance mode at 292 nm. The linear regression analysis data for the calibration plots showed good linear relationship with r = 0.9953 with respect to peak area in the concentration range of 400-1200 ng spot⁻¹. The mean value (±S.D.) of slope and intercept were 9.66 ± 0.05 and 956.33 ± 27.67, respectively. The method was validated for precision, accuracy, ruggedness and recovery. The limits of detection and quantitation were 2.73 and 8.27 ng spot⁻¹, respectively. Gatifloxacin was subjected to acid and alkali hydrolysis, oxidation, photodegradation and dry heat treatment. The drug undergoes degradation under acidic and basic conditions and upon wet and dry heat treatment. The degraded products were well separated from the pure drug. The statistical analysis proves that the developed method for quantification of gatifloxacin as bulk drug and from polymeric nanoparticles is reproducible and selective. As the method could effectively separate the drug from its degradation products, it can be employed as stability-indicating one.     

CtrA gene based electrochemical DNA sensor for detection of meningitis

Electrochemical DNA sensor has been fabricated by immobilizing thiolated single stranded oligonucleotide (ssDNA) probe onto gold (Au) coated glass electrode for meningitis detection using hybridization with complementary DNA (CtrA) in presence of methylene blue (MB). These electrodes (ssDNA/Au and dsDNA/Au) have been characterized using atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FT-IR), electrochemical impedance spectroscopy (EIS) and cyclic voltammetric (CV) technique. The DNA/Au electrode can detect the complementary DNA in the range of 7–42 ng/μl in 5 min (hybridization) with response time 60 s and electrode is stable for about 4 months when stored at 4 °C. The sensitivity of dsDNA/Au electrode is 115.8 μA/ng with 0.917 regression coefficient (R).     

New collective modes in multiferroic TbMnO3: The electromagnons

Using a phenomenological Landau theory as well as equations of motion, we look for new excitations in the multiferroic TbMnO₃. Coupling these excitations to an electromagnetic field, we derived the magneto–polariton dispersion relation. Further, the frequency as well as temperature dependent dielectric susceptibility, and hence the refractive index, are obtained in this formulation. The imaginary part of the latter is computed and compared with the existing experimental data.