Photoinduced phenomena in layer-by-layer films of poly(allylamine hydrochloride) and Brilliant Yellow azodye

The nanoscale interactions between adjacent layers of layer-by-layer (LBL) films from poly(allylamine hydrochloride) (PAH) and azodye Brilliant Yellow (BY) have been investigated, with the films employed for optical storage and the formation of surface-relief gratings. Using Fourier transform infrared spectroscopy, we identified interactions involving SO3- groups from BY and NH3+ groups from PAH. These electrostatic interactions were responsible for the slow kinetics of writing in the optical storage experiments, due to a tendency to hinder photoisomerization and the subsequent reorientation of the azochromophores. The photoinduced birefringence did not saturate after one hour of exposure to the writing laser, whereas in azopolymer films, saturation is normally reached within a few minutes. on the other hand, the presence of such interactions prevented thermal relaxation of the chromophores after the writing laser was switched off, leading to a very stable written pattern. Moreover, the nanoscale interactions promoted mass transport for photoinscription of surface-relief gratings on PAH/BY LBL films, with the azochromophores being able to drag the inert PAH chains when undergoing the trans-cis-trans photoisomerization cycles. A low level of chromophore degradation was involved in the SRG photoinscription, which was confirmed with micro-Raman and fluorescence spectroscopies.

Preparation of Pb(Zr,Ti)O-3 thin films by soft chemical route

Lead zirconate titanate, Pb(Zr0.3Ti0.7)O-3 (PZT) thin films were prepared with success by the polymeric precursor method. Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FT-IR), Micro-Raman spectroscopy and X-ray diffraction (XRD) were used to investigate the formation of the PZT perovskite phase. X-ray diffraction revealed that the film showed good crystallinity and no presence of secondary phases was identified. This indicates that the PZT thin films were crystallized in a single phase. PZT thin films showed a well-developed dense grain structure with uniform distribution, without the presence of rosette structure. The Raman spectra undoubtedly revealed these thin films in the tetragonal phase. For the thin films annealed at the 500-700 degreesC range, the vibration modes of the oxygen sublattice of the PZT perovskite phase were confirmed by FT-IR. The room temperature dielectric constant and dielectric loss of the PZT films, measured at 1 kHz were 646 and 0.090, respectively, for thin film with 365 nm thickness annealed at 700 degreesC for 2 h. A typical P-E hysteresis loop was observed and the measured values of P-s, P-r and E-c were 68 muC/cm(2), 44 muC/cm(2) and 123 kV/cm, respectively. The leakage current density was about 4.8 x 10(-7) A/cm(2) at 1.5 V. (C) 2003 Elsevier Ltd. All rights reserved.

Effects of post-annealing on the dielectric properties of Au/BaTiO3/Pt thin film capacitors

Barium titanate thin films were prepared by the polymeric precursor method and deposited onto Pt/Ti/SiO2/Si substrates. X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FT-IR) and micro-Raman spectroscopy were used to investigate the formation of the BaTiO3 perovskite phase. Afterwards, the films were submitted to post-annealing treatments in oxygen and nitrogen atmospheres at 300 degreesC for 2 h, and had their dielectric properties measured. It was observed that the electric properties of the thin films are very sensitive to the nature of the post-annealing atmosphere. This study demonstrates that post-annealing in an oxygen atmosphere increases the dielectric relaxation phenomenon and that post-annealing in a nitrogen atmosphere produces a slight dielectric relaxation. (C) 2004 Elsevier B.V All rights reserved.

Sufentanil-2-hydroxypropyl-beta-cyclodextrin inclusion complex for pain treatment: Physicochemical, cytotoxicity, and pharmacological evaluation

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

A Novel Plasma Technique for Surface Treatment: The Plasma Expander

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Thermal behaviour of fumaric acid, sodium fumarate and its compounds with light trivalent lanthanides in air atmosphere

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Quercetin-PVP K25 solid dispersions: Preparation, thermal characterization and antioxidant activity

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Er(3+) doped phosphoniobate glasses and planar waveguides: structural and optical properties

Phosphoniobate glasses with composition (mol%) (100-x) NaPO(3)-xNb(2)O(5) ( x varying from 11 to 33) were prepared and characterized by means of thermal analysis, Fourier transform infrared spectroscopy, Raman scattering and (31)P nuclear magnetic resonance. The addition of Nb(2)O(5) to the polyphosphate base glass leads to depolymerization of the metaphosphate structure. Different colors were observed and assigned as indicating the presence of Nb(4+) ions, as confirmed by electron paramagnetic resonance measurements. The color was observed to depend on the glass composition and melting temperature as well. Er(3+) containing samples were also prepared. Strong emission in the 1550 nm region was observed. The Er(3+4)I(15/2) emission quantum efficiency was observed to be 90% and the quenching concentration was observed to be 1.1 mol%( 1.45 x 10(20) ions cm(-3)). Planar waveguides were prepared by Na(+)-K(+)-Ag(+) ion exchange with Er(3+) containing samples. Optical parameters of the waveguides were measured at 632.8, 543.5 and 1550 nm by the prism coupling technique as a function of the ion exchange time and Ag(+) concentration. The optimized planar waveguides show a diffusion depth of 5.9 mu m and one propagating mode at 1550 nm.

Thermoanalytical study of some anti-inflammatory analgesic agents

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Structure and properties of conducting bacterial cellulose-polyaniline nanocomposites

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Preparation and thermal characterization of inclusion complex of Brazilian green propolis and hydroxypropyl-beta-cyclodextrin

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Er(3+)-Based Diureasil Organic-Inorganic Hybrids

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Photoluminescent properties of lead zirconate powders obtained by the polymeric precursor method

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Preparation of CeO2 by a simple microwave-hydrothermal method

Cerium carbonate hydroxide (orthorhombic Ce(OH)CO3) hexagonal-shaped microplates were synthesized by a simple and fast microwave-hydrothermal method at 150 degrees C for 30 min. Cerium nitrate, urea and cetyltrimethylammonium bromide were used as precursors. Ceria (cubic CeO2) rhombus-shape was obtained by a thermal decomposition oxidation process at 500 degrees C for 1 h using as- synthesized Ce(OH)CO3. The products were characterized by X-ray powder diffraction, field-emission scanning electron microscopy, thermogravimetric analysis and Fourier transformed infrared spectroscopy. The use of microwave-hydrothermal method allowed to obtain cerium compounds at low temperature and shorter time compared to other synthesis methods. (C) 2008 Elsevier B.V. All rights reserved.

Synthesis, characterization, crystal structure, and biological studies of vanadium complexes with glycolic acid

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)