A. P. Ayala

Raman study of morphotropic phase boundary in PbZr 1 − x Ti x O 3 at low temperatures

The Raman spectra of

Raman investigation of A2CoBO6 (A=Sr and Ca, B=Te and W) double perovskites

{\mathrm{PbZr}}_{1\ensuremath{-}x}{\mathrm{Ti}}_{x}{\mathrm{O}}_{3}

Raman investigations of rare earth orthovanadates

ceramics with titanium concentration varying between

Monoclinic phase ofPbZr0.52Ti0.48O3ceramics: Raman and phenomenological thermodynamic studies

x=0.40

The encapsulation of β-lapachone in 2-hydroxypropyl-β-cyclodextrin inclusion complex into liposomes: a physicochemical evaluation and molecular modeling approach.

and 0.60 were measured at 7 K. By observing the concentration-frequency dependence of the vibrational modes, we identified the boundaries among the rhombohedral, monoclinic, and tetragonal ferroelectric phases. The analysis of the spectra was made in the view of group theory analysis making possible the assignment of some modes for the monoclinic phase.

Spin-phonon coupling in Y2NiMnO6 double perovskite probed by Raman spectroscopy

Raman scattering is used to investigate the room temperature phonons of tetragonal (I4∕m) Sr2CoWO6 and monoclinic (P21∕n) Ca2CoWO6, Sr2CoTeO6, and Ca2CoTeO6 double perovskites. Both tetragonal and monoclinic structures result from small distortions of the Fm3¯m cubic lattice. Therefore, phonons were assigned according to correlations with those observed in the prototype A2B′B″O6 Fm3¯m cubic structure and the internal vibrational modes of the oxygen octahedra. The observed shifts of some vibrations in the A2CoBO6 compounds upon changing either A or B elements are tentatively explained.Raman scattering is used to investigate the room temperature phonons of tetragonal (I4∕m) Sr2CoWO6 and monoclinic (P21∕n) Ca2CoWO6, Sr2CoTeO6, and Ca2CoTeO6 double perovskites. Both tetragonal and monoclinic structures result from small distortions of the Fm3¯m cubic lattice. Therefore, phonons were assigned according to correlations with those observed in the prototype A2B′B″O6 Fm3¯m cubic structure and the internal vibrational modes of the oxygen octahedra. The observed shifts of some vibrations in the A2CoBO6 compounds upon changing either A or B elements are tentatively explained.

Structural and dielectric properties of Nd3+-doped Ba0.77Ca0.23TiO3 ceramics

Polarized Raman spectroscopy has been used to obtain the room-temperature phonon spectra of the series of rare earth orthovanadate single crystals: SmVO4, HoVO4, YbVO4, and LuVO4. The observed Raman frequencies follow the overall mode distribution expected for REVO4 compounds with the tetragonal zircon structure. The variation of the mode frequency with atomic number across the lanthanide orthovanadate series was investigated, and the trend exhibited by the internal modes was explained by considering the force constants of VO4 tetrahedron.

High‐pressure Raman study of taurine crystal

This work reports on the first Raman detection of the tetragonal to monoclinic phase transition in PZT ceramics near morphotropic phase boundary at low temperatures. The transition is characterized by changes in the frequency of lattice modes with the temperature. The results presented here confirm the previous one recently reported by Noheda et al. using high-resolution synchrotron X-ray powder diffraction technique and dielectric measurements. The stability of the new phase is discussed within the framework of phenomenological Landau-Devonshire Theory.

Molecular Structure and Vibrational Spectroscopic Investigation of Secnidazole Using Density Functional Theory

The aim of this study was to encapsulate lapachone (β-lap) or inclusion complex (β-lap:HPβ-CD) in liposomes and to evaluate their physicochemical characteristics. In addition, the investigation of the main aspects of the interaction between β-lap and 2-hydroxypropyl-β-cyclodextrin (HPβ-CD), using both experimental and molecular modeling approaches was discussed. Furthermore, the in vitro drug release kinetics was evaluated. First, a phase solubility study of β-lap in HPβ-CD was performed and the β-lap:HPβ-CD was prepared by the freeze-drying technique. A 302-fold increase of solubility was achieved for β-lap in HPβ-CD solution with a constant of association K(1:1) of 961 M(-1) and a complexation efficiency of β-lap of 0.1538. (1)H NMR, TG, DSC, IR, Raman and SEM indicated a change in the molecular environment of β-lap in the inclusion complex. Molecular modeling confirms these results suggesting that β-lap was included in the cavity of HPβ-CD, with an intermolecular interaction energy of -23.67 kJ mol(-1). β-lap:HPβ-CD and β-lap-loaded liposomes presented encapsulation efficiencies of 93% and 97%, respectively. The kinetic rate constants of 183.95±1.82 μg/h and 216.25±2.34 μg/h were calculated for β-lap and β-lap:HPβ-CD-loaded liposomes, respectively. In conclusion, molecular modeling elucidates the formation of the inclusion complex, stabilized through hydrogen bonds, and the encapsulation of β-lap and β-lap:HPβ-CD into liposomes could provide an alternative means leading eventually to its use in cancer research.

Raman and infrared spectroscopic studies of the Li3Na3In2F12 fluoride garnet

Temperature-dependent Raman spectroscopy measurements in Y2NiMnO6 ceramics were performed in the 20 K–850 K range. A detailed analysis of the temperature dependence of the phonon energy of the oxygen octahedra stretching mode shows an anomalous softening below the Curie temperature. This effect was ascribed to a spin-phonon coupling, suggesting that the oxygen octahedra stretching vibrational mode stabilizes the magnetic interaction. The observed spin-phonon coupling is stronger than those reported in other Re2NiMnO6 double perovskites, suggesting that the rare earth ionic radius is not the unique parameter influencing the magnitude of this effect.