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1.
A. Ferreira da Silva I. Pepe S.A. Tomás W.M. de Azevedo R. Ahuja 《Applied Surface Science》2006,252(15):5365-5367
In this paper we present spectroscopic properties of doped and undoped titanium dioxide (TiO2) as nanofilms prepared by the sol-gel process with rhodamine 6G doping and studied by photoacoustic absorption, excitation and emission spectroscopy. The absorption spectra of TiO2 thin films doped with rhodamine 6G at very low concentration during their preparation show two absorption bands, one at 2.3 eV attributed to molecular dimmer formation, which is responsible for the fluorescence quenching of the sample and the other at 3.0 eV attributed to TiO2 absorption, which subsequently yields a strong emission band at 600 nm. The electronic band structure and optical properties of the rutile phase of TiO2 are calculated employing a fully relativistic, full-potential, linearized, augmented plane-wave (FPLAPW) method within the local density approximation (LDA). Comparison of this calculation with experimental data for TiO2 films prepared for undoped sol-gels and by sputtering is performed. 相似文献
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The extraction of Al(III) and Zn(II) from an aqueous solution with two water-in-oil microemulsions, one containing di(2-ethylhexyl)phosphoric acid (DEHPA), was investigated to aid the understanding of the role of the extractant and the metal specific characteristics in the mechanism of microemulsion extraction. The extraction of Al with the DEHPA microemulsion increased by a factor of about 10 with respect to that in the conventional DEHPA system, whereas the extraction of Zn was lower than that in the single DEHPA system. Extraction with the DEHPA-free microemulsion was very low, showing that metal ion solubilization was not important in the mechanism of microemulsion extraction. It is proposed that the effect of the mixed microemulsion on the metal distribution coefficient is the result of the balance between a decrease in the complexation reaction yield due to the interaction between butanol and DEHPA, and the adsorption of the metal complex at the macro- and microinterfaces. The former leads to a decrease in Zn(II) extraction and the latter to Al(III) extraction synergism. Copyright 2000 Academic Press. 相似文献
5.
Coordination compounds of mercury(II) chloride, bromide, cyanide and thiocyanate with N-methylnicotinamide, a potentially
bidentate ligand, have been prepared. The complexesisolated have 1∶1 (metal:ligand)stoichiometry. Molecular weight measurements
in molten camphor indicate that the mercury (II) chloride and bromide complexes are monomeric. Based on conductance values,
molecular weight determinations and infrared spectral data, it is inferred that in the solid state in all these complexes
the metal ion has a coordination number three and is bonded to the N-methylnicotinamide via its pyridine ring nitrogen, and
is terminally bonded to the halogen/pseudohalogens. 相似文献
6.
A high-performance thin layer chromatographic (HPTLC) method for the rapid and simple quantification of the four major anthraquinone derivatives i.e. physcion, chrysophanol, emodin and chrysophanol glycoside in Rheum emodi is described. HPTLC of anthraquinone derivatives was performed on pre-coated RP-18 F254S HPTLC plates. For achieving good separation, the mobile phase of methanol-water-formic acid (80:19:1, v/v/v) was used. The densitometric determination of anthraquinone derivatives was carried out at 445 nm in reflection/absorption mode. The calibration curves were linear in the range of 20-100 ng for physcion, 80-400 ng for chrysophanol and emodin, and 200-1000 ng for chrysophanol glycoside. The method was found to be reproducible and convenient for quantitative analysis of anthraquinone derivatives in the methanolic extract of rhizomes of R. emodi collected from three different locations of Western Himalaya, India. 相似文献
7.
Abstract Platinum is studied, theoretically, under very high compression. The calculated equation of state is found to agree well with the recent experimental data. At V/V0 = 0.4, where V0 is the experimental equilibrium volume, we find a transition from the face centered cubic structure (fcc), found at ambient pressure, to the body centered cubic structure (bcc). The calculated transition pressure is 26 Mbar. The stabilization of the bcc structure is explained by the eigen value sum. 相似文献
8.
Shadab Md. Alka Ahuja Roop K. Khar Sanjula Baboota Krishna Chuttani 《Journal of Dispersion Science and Technology》2013,34(9):1318-1324
Mucoadhesive chitosan microspheres of acyclovir were prepared to prolong the gastric residence time using simple emulsification phase separation technique. The particle morphology of drug-loaded formulations was measured by SEM and the particle size distribution was determined using an optical microscope. The release profile of acyclovir from microspheres was examined in simulated gastric fluid (SGF pH 1.2). The particles were found to be discreet and spherical with the maximum particles of an average size (31.62 ± 4.64). The entrapment efficiency was found to be in the range of 40.24 to 67.29%. The concentration of the glutaraldehyde (25%v/v) as a cross-linker 2 ml and drug polymer ratio of 1:2 caused an increase in the entrapment efficiency and the extent of drug release. The optimized chitosan microspheres were found to possess good bioadhesion (79.89 ± 1.01%). The gamma-scintigraphy study showed the gastric residence time of more than 6 hours which revealed that optimized formulation could be a good choice for gastroretentive systems. 相似文献
9.
A phase transition was observed at 63-69 GPa and room temperature in vanadium with synchrotron x-ray diffraction. The transition is characterized as a rhombohedral lattice distortion of the body-centered-cubic vanadium without a discontinuity in the pressure-volume data, thus representing a novel type of transition that has never been observed in elements. Instead of driven by the conventional s-d electronic transition mechanism, the phase transition could be associated with the softening of C44 trigonal elasticity tensor that originates from the combination of Fermi surface nesting, band Jahn-Teller distortion, and electronic topological transition. 相似文献
10.
L. Vadkhiya M.K. Bhayani B.L. Ahuja 《Journal of magnetism and magnetic materials》2010,322(19):2857-2867
We have computed spin-dependent energy bands, spin moments and density of states of NiAs-type CrX (X=S, Se and Te) chalcogenides using linear combination of atomic orbitals method within density functional theory as well as full potential augmented plane wave method. In addition, magnetic properties have also been computed using spin polarized relativistic Korringa-Kohn-Rostoker method. We have also obtained the first ever theoretical electron momentum densities of CrX compounds considering linear combination of atomic orbitals and compared the results with the isotropic Compton profiles measured using 20 Ci 137Cs Compton spectrometer. The Fermi surface topology and magnetic properties are discussed in terms of majority and minority energy bands and density of states. In addition, to highlight the role of Cr (3d) electrons in such type of chalcogenides, we have also reported the magnetic Compton profile of CrTe using the Korringa-Kohn-Rostoker method. 相似文献