Excess parameters for binary mixtures of alkyl benzoates with 2-propanol at different temperatures

Density (ρ), viscosity (η), and speed of sound (U) values for the binary mixture systems of methyl benzoate + 2-propanol and ethyl benzoate + 2-propanol including those of pure liquids were measured over the entire mole fraction range at five different temperatures (303.15, 308.15, 313.15, 318.15, and 323.15) K. From these experimentally determined values, various thermo-acoustic parameters such as excess isentropic compressibility $ \left( {K_{\text{s}}^{\text{E}} } \right) $ , excess molar volume (V ^E) and excess free length $ \left( {L_{\text{f}}^{\text{E}} } \right) $ , excess Gibb’s free energy (ΔG ^*E), and excess enthalpy (H ^E) have been calculated. The excess functions have been fitted to the Redlich–Kister type polynomial equation. The deviations for excess thermo-acoustic parameters have been explained on the basis of the intermolecular interactions present in these binary mixtures. The theoretical values of speed of sound in the mixtures have been evaluated using various theories and have been compared with experimentally determined speed of sound values in order to check the applicability of such theories to the liquid mixture systems under study. Viscosity data have been used to test the applicability of standard viscosity models of Grunberg–Nissan, Hind–Mc Laughlin, Katti–Chaudhary, Heric and Brewer, Frenkel, Tamura and Kurata at various temperatures for the binary liquid systems under study.     

Conductivity studies of poly(ethylene oxide)(PEO)/poly(vinyl alcohol) (PVA) blend gel polymer electrolytes for dye-sensitized solar cells

Poly(ethylene oxide)(PEO)–poly(vinyl alcohol) (PVA) blend-based gel polymer electrolytes (GPEs) have been prepared by blending equal weights of PEO and PVA in ethylene carbonate (EC), dimethyl sulfoxide (DMSO), tetrabutylammonium iodide (TBAI), and iodine crystals (I₂). The conductivity, diffusion coefficient, number density, and ion mobility of the electrolytes have been calculated from the impedance data obtained from electrochemical impedance spectroscopy (EIS) measurements. The GPE with the composition of 7.02 wt%, PVA, 7.02 wt% PEO, 30.11 wt% ethylene carbonate (EC), 30.11 wt% DMSO, 24.08 wt% TBAI and 1.66 wt% I₂ exhibits the highest conductivity of 5.5 mS cm^?1 at room temperature. Dye-sensitized solar cells (DSSCs) with configuration fluorine tin oxide (FTO)/titanium dioxide/N3-dye/GPE/platinum/FTO have been fabricated and tested under the white light of intensity 100 mW cm^?2. The DSSC containing the highest conducting GPE exhibits the highest power conversion efficiency, η of 5.36 %.     

Synthesis and mesomorphic behavior of benzothiazole-based liquid crystals having terminal methoxyl group

A homologous series of benzothiazole derivatives, 6-methoxy-2-(4-alkanoyloxybenzylidenamino)benzothiazoles, were synthesized and characterized using FT-IR, ¹H and ¹³C NMR, mass spectrometry and elemental analysis. Enantiotropic nematic phase was observed throughout the entire series. Smectic C phase only emerged from the decanoyloxy derivative onwards. The terminal methoxyl group and the ester linkage influenced the mesomorphic behavior of the present series.     

Temperature dependence of absorption edge anisotropy in 2H- MoSe2 layered semiconductors

The absorption-edge anisotropy of 2H- MoSe₂ was studied by photoconductivity (PC) measurements as a function of temperature in the range of 12-300 K. A significant shift towards lower energies has been observed in the PC spectra on the edge plane with respect to those corresponding to the van der Waals (VdW) plane. The parameters that describe the temperature dependence of the absorption edges are evaluated by the Bose-Einstein empirical expression. Effective phonon energy was estimated from the temperature dependence of the Urbach energy. The estimated effective phonon energy for the VdW and edge planes, respectively, can be correlated to the observed Raman active and modes.     

Synthesis and mesomorphic properties of new Schiff base esters with different alkyl chains

A new series of Schiff base esters,4-(dimethylamino)benzylidene-4'-alkanoyloxyanilines containing even number of carbons at the end group of the molecules(C_(n-1)H_(2n-1)COO,n = 6,8,10,12,14,16,18) were synthesized.The present compounds were monotropic liquid crystals.It was also found that the end groups of the molecules had effect on the mesomorphic properties.     

Rapid thermal annealing effects on the structural and optical properties of ZnO films deposited on Si substrates

The structural and optical properties of ZnO films deposited on Si substrate following rapid thermal annealing (RTA) have been investigated by X-ray diffraction (XRD), atomic force microscopy (AFM), and photoluminescence (PL) measurements. After RTA treatment, the XRD spectra have shown an effective relaxation of the residual compressive stress, an increase of the intensity and narrowing of the full-width at half-maximum (FWHM) of the (0 0 2) diffraction peak of the as-grown ZnO film. AFM images show roughening of the film surface due to increase of grain size after RTA. The PL spectrum reveals a significant improvement in the UV luminescence of ZnO films following RTA at 800 °C for 1 min.     

Enantiomeric pairs of copper(II) polypyridyl-alanine complex salts: anticancer studies

The anticancer properties of two previously characterized pairs of optically pure chiral complex salts [Cu(phen)(ala)(H₂O)]X·xH₂O (phen?=?1.10-phenanthroline; X?=?NO₃^?; ala: l-alanine (l-ala) 1 and d-alanine (d-ala) 2; and (X?=?Cl^?; ala: l-ala, 3 and d-ala, 4; x?=?number of lattice water molecules) are reported herein, together with the crystal structure of the d-enantiomer 4. Unlike cisplatin which is ineffective against MCF-7 cancer cells with the absence of caspase-3 protein expression, these two pairs of complex salts were effective against this cell line and they were able to induce an increase in intracellular ROS, loss in mitochondrial membrane potential, cell cycle arrest mainly at SubG1 phase , caspase-9 activation, and caspase-3/caspase-7-independent apoptosis. Screening of 1 on the NCI-60 panel of human cancer cell lines showed that it was effective against most of the cell lines. MTT-NCI modified assay screening was also done on other cancer cell lines, viz. A549, CNE1, and HepG2, and two normal cell lines, viz. MCF-10A and CHANG. The effects of chirality of these Cu(II) compounds, especially the greater selectivity of d-enantiomers over the l-counterparts, on their anticancer properties are also reported herein.     

Image analysis method to study electro-optic parameters of nematogens

This paper demonstrated the image analysis technique for the investigation of electro-optic behaviour of homogeneously aligned nematic liquid crystals p-n alkyl benzoic acids (nBA) where n = 5 and 6 under the application of direct current (DC) electric field. Textures of the liquid crystals in the mesophase region of particular temperature were recorded in three monochromatic image planes at the wavelengths of 635 (red), 530 (green) and 475 nm (blue) as a function of applied DC voltage. Electro-optic properties such as transmittance, birefringence, phase retardation and contrast ratio were measured by analysing the optical intensities of the recorded textures using MATLAB software. The changes in the textural features and formation of new textures as a function of voltage provided information for better understanding of the electro-optic characteristics of liquid crystals. Results of this study were compared with the data of the other standard techniques: laser source (633 nm) experiment and United Detector Technology (UDT) sensor of model UV- 35P silicon photo diode which uses white light as source and filters the wavelengths using three colour filters of wavelengths 635, 530 and 475nm.     

Conformational studies of intermolecular hydorgen bonding through induced crystal G phase in nBA:7HB

This paper exploits the physical investigation on liquid crystal complexes obtained by self-organisation of p-n-alkyl benzoic acid (nBA) mesogens with non-mesogenic materials heptyl p-hydroxy benzoate (7HB). Intermolecular interactions of the molecules result the hydrogen bond between the proton donor (COOH) of nBA and proton acceptor (OH) of 7HB. The formation of hydrogen bond is attributed to the quenching of the nematic phase and inducement of crystal G phase in liquid crystal complex. A comparative study of phase abundance is presented with respect to the pure nBAs and other hydrogen bonded liquid crystal complexes of nBAs. Thermal and phase behaviour of the complexes are determined by polarising optical microscope (POM), differential scanning calorimetry (DSC) and image moments approach. Intermolecular interactions which result the hydrogen bond in complexes are investigated using Fourier transform infrared (FTIR) spectroscopy. Molecular structure of the liquid crystal complexes in the solid phase was elucidated using powder X-ray diffraction and proton nuclear magnetic resonance (¹HNMR).     

Scaling effects on the dynamic characteristics of long-wavelength vertical-cavity surface-emitting lasers (VCSELs)

The influence of the oxide aperture radius on the characteristics of a long-wavelength vertical-cavity surface-emitting laser (VCSEL) lasing at 1550 nm is presented in this paper. While previous works in the literature mostly investigate the scaling effects of short-wavelength VCSELs. The importance of studying the effects of long-wavelength operation should not be underestimated, as it could be used in fiber optics communication to mitigate dispersion and attenuation of the channel. Using the oxide-confined VCSEL model, the dynamic operations were examined taking into account the carrier-noise, photon-noise and phase-noise, including feedback of the external cavity. Our simulations show that by reducing the oxide aperture up to a given optimal radius, an improvement in the device's characteristics can be demonstrated. Below this value, performance degradation is expected due to increased diffraction losses, reduced confinement factor and enhanced spontaneous emission.