Filmes delgados luminescentes obtidos a partir de hidroxicarbonatos de ítrio ativados por európio ou térbio

These films were obtained by dip coating. Parameters like dislocation velocity; number of deposits, suspension concentration, and number of deposits followed or not by heat treatment between each deposit and calcination temperature were evaluated for establishing the best homogeneity. The obtained films were characterized in terms of their morphology, optical quality and photoluminescence by scanning electron microscopy (SEM), UV-vis absorption spectrophotometry and luminescence spectroscopy, respectively. The morphologic and luminescent characteristics showed dip coating as good laboratory technique for development of thin films for optical applications.

Filmes na formação de futuros professores: educar o olhar

Neste artigo, trago parte de minha experiência como professora de futuros professores de Matemática quando ministrei a disciplina Didática, no ano de 2010. Socializo aqui algumas das práticas instituídas nesse contexto e que resgatam a potencialidade dos filmes e da escrita no processo formativo dos alunos. Problematizo a importância de assistir juntos a um filme, já que essa experiência estética possibilita promover o conhecimento, o sentimento e a ação. Trago a voz dos meus alunos, documentada nos registros semanais elaborados por eles, para dizer das marcas que os filmes deixaram no percurso formativo de cada um como futuros professores de Matemática. Ao resgatar essa prática, enfatizo a importância de educar o olhar na busca pela constituição de um professor comprometido com uma educação e uma sociedade mais justa e democrática.

Influência do tipo de coleta (comum ou seletiva) na reciclagem de filmes de poliolefinas pós-consumo

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

Biodegradação de filmes de PP/PCL em solo e solo com chorume

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

Filmes finos de Titanato de Chumbo e Lantânio - PLT: influência do pH

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

Filmes finos de SrBi2Ta2O9 processados em forno microondas

Filmes finos de SrBi2Ta2O9 foram depositados em substratos de Pt/Ti/SiO2/Si e, pela primeira vez, sinterizados em forno microondas doméstico. Os padrões de difração de raios X mostraram que os filmes são policristalinos. O processamento por microondas permite utilizar baixa temperatura na síntese e obter filmes com boas propriedades elétricas. Ensaios de microscopia eletrônica de varredura (MEV) e de Força Atômica (MFA) revelam boa aderência entre filme e substrato, com microestrutura de superfície apresentando grãos finos e esféricos e rugosidade de 4,7 nm. A constante dielétrica e o fator de dissipação, para freqüência de 100 KHz, à temperatura ambiente, foram de 77 e 0,04, respectivamente. A polarização remanescente (2Pr) e o campo coercitivo (Ec) foram 1,04 miC/cm² e 33 kV/cm. O comportamento da densidade de corrente de fuga revela três mecanismos de condução: linear, ôhmico e outro mecanismo que pode ser atribuído à corrente de Schottky. Dos padrões de DRX, análises das imagens por MEV e topografia de superfície por MFA observa-se que 10 min de tratamento térmico a 550 ºC, em forno microondas, é tempo suficiente para se obter a cristalização do filme.

Sinterização de filmes finos de LiNbO3 em forno microondas: estudo da influência da direção do fluxo de calor

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

Surface pressure-area isotherms for Langmuir monolayers and a docking molecular orientation of perylene tetracarboxylic derivatives on a water surface

The surface pressure-molecular area (pi-A) isotherms for Langmuir monolayers of four perylenetetracarboxylic (PTCD) derivatives, measured with varying subphase temperatures and compression speeds, are reported. The behavior of these PTCD derivatives at the water-air interface is modeled using the rigid docking method. This approach is the first attempt to model the molecular orientation of PTCD on the water surface to be compared with experimental Langmuir isotherms. Through this methodology, it would be possible to anticipate aggregation and determine if favorable spatial orientations of perylenes are generated on the water surface. The pi-A isotherm experiments show that these molecules can support high surface pressures, indicating strong packing on the water surface and that the isotherms are compression speed independent but temperature dependent. The molecular orientation and stacking was further examined in Langmuir-Blodgett (LB) monolayers deposited onto glass and glass coated with Ag island films using UV-visible absorption and surface-enhanced fluorescence (SEF) measurements.

The use of Langmuir-Blodgett films of a perylene derivative and polypyrrole in the detection of trace levels of Cu2+ ions

Langmuir films of a tetracarboxylic perylene derivative and polypyrrole display condensed surface pressure isotherms that are shifted when Cu2+ ions are added to the ultrapure water subphase. These films were transferred onto interdigitated gold electrodes leading to Y-type Langmuir-Blodgett (LB) films. The electrodes modified with 5-layer LB films were immersed into a flask with ultrapure water and water containing Cu2+ ions at concentrations ranging from mM to muM. Impedance measurements indicated a distinct electrical response for the two types of films. Although the materials chosen have no specificity for ionic metals, they can be combined for detecting trace levels of Cu2+, which may be exploited in water quality monitoring. (C) 2004 Elsevier B.V. All rights reserved.

Langmuir and langmuir-blodgett films of polyfluorenes and their use in polymer light-emitting diodes

The Langmuir and Langmuir-Blodgett (LB) film properties of two polyfluorene derivatives, namely poly(2,7-9,9'-dihexylfluorene-dyil) (PDHF) and poly(9,9 dihexylfluorene-dyil-vynilene-alt-1,4-phenylene-vyninele) (PDHF-PV), are reported. Surface pressure (Pi-A) and surface potential (Delta V-A) isotherms indicated that PDHF-PV forms true monolayers at the air/water interface, but PDHF does not. LB films could be transferred onto various types of substrate for both PDHF and PDHF-PV. Only the LB films from PDHF-PV could withstand deposition of a layer of evaporated metal to form a light-emitting diode (PLED), which had typical rectifying characteristics and emitted blue light. It is inferred that the ability of the polymer to form true monomolecular layers at the air/water interface seems to be associated with the viability of the LB films in PLEDs.

Temperature dependence of photoinduced birefringence in mixed Langmuir-Blodgett (LB) films of azobenzene-containing polymers

The temperature dependence of photoinduced birefringence was investigated for mixed Langmuir-Blodgett (LB) films from the homopolymer poly[4'-[[2-(methacryloyloxy)ethyl]ethyl-amino]-2-chloro-4-nitroazobenzene] (HPDR13) and cadmium stearate (Cdst) and from the copolymer 4-[N-ethyl-N-(2-hydroxyethyl)]amino-2'-chloro-4'-nitroazobenzene (MMA-DR13) and CdSt. Birefringence was achieved by impinging a linearly polarized light on the LB films. The maximum birefringence achieved decreased with temperature as thermal relaxation of the chromophores was facilitated. The buildup curves for birefringence were fitted with biexponential functions representing distinctly different mechanisms with time constants. The first, fast process is thermally activated and may be represented by an Arrhenius process. The decay of birefringence after switching off the laser source was described by a Kohlraush-Williams-Watts (KWW) function, consistent with a distribution of relaxation times for the polymer system. Activation energies were obtained from Arrhenius plots of the rate constant of the exponential functions and KWW function, which showed that the buildup of birefringence was very similar for the two polymer systems. The decay, however, was slower for the LB film from MMA-DR13/CdSt. (C) 2002 Published by Elsevier B.V. Ltd.

Preparation, characterization and taste sensing properties of Langmuir-Blodgett Films from mixtures of polyaniline and a ruthenium complex

Langmuir-Blodgett (LB) films from a ruthenium complex, mer-[RuCl3(dppb)(py)] (dppb = PPh2(CH2)(4)PPh2; py = pyridine) (Rupy), and from mixtures with varied amounts of polyaniline (PANi) were fabricated. Molecular-level interactions between the two components are investigated by surface potential, dc conductivity and Raman spectroscopy measurements, particularly for the mixed film with 10% of Rupy. For the latter, the better miscibility led to an interaction with Rupy inducing a decrease in the conducting state of PANi, as observed in the Raman spectra and conductivity measurement. The interaction causes the final film properties to depend on the concentration of Rupy, and this was exploited to produce a sensor array made up of sensing units consisting of 11-layer LB films from pure PANi, pure Rupy and mixtures with 10 and 30% of Rupy. It is shown that the combination of only four non-specific sensing units allows one to distinguish the basic tastes detected by biological systems, viz. saltiness, sweetness, sourness and bitterness, at the muM level. (C) 2003 Elsevier B.V. Ltd. All rights reserved.

Soliton model for proton conductivity in Langmuir films

A soliton model for proton conductivity in Langmuir films is presented. The model contains three real scalar fields describing the hydrogen involved in the conduction, the hydrophilic head of the Langmuir film, and the water. Soliton solutions that describe proton motion along the hydrogen bonds are found. Under compression of the film, the distance between the minima of the proton potential and the strength of the hydrogen bonds between the film molecule and the water are changed. Such changes increase the probability of soliton creation. The model. presented allows proton conductivity data in Langmuir films to be explained. (C) 2001 Published by Elsevier B.V. B.V.

Morphological characterization of Langmuir-Blodgett films from polyaniline and a ruthenium complex (Rupy): influence of the relative concentration of Rupy

We report on the use of dynamic scale theory and fractal analyses in a study of the growth stages of Langmuir-Blodgett (LB) films of polyaniline and a neutral biphosphinic ruthenium complex, namely mer-[ RuCl3 (dppb)(py)] (dppb = 1,4-bis(diphenylphosphine) buthane, py = pyridine), Rupy. The LB films were deposited onto indium-tin-oxide substrates and characterized with atomic force microscopy. From the granular morphology exhibited by the films one could infer growth processes inside and outside the grains. Growth outside was found to follow the Kardar-Parisi-Zhang model, with fractal dimensions of about 2.7. As one would expect, inside the grains the morphology is close to a Euclidian surface with fractal dimension of about 2.

Surface morphology and molecular organization of lignins in Langmuir-Blodgett films

Atomic force microscopy (AFM) and Fourier transform infrared spectroscopy (FTIR) are used to investigate molecular organization in Langmuir-Blodgett (LB) films of two kinds of lignins. The lignins were extracted from sugar cane bagasse using distinct extraction processes and are referred to here as ethanol lignin (EL) and saccharification lignin (SAC). AFM images show that LB films from EL have a flat surface in comparison with those from SAC. For the latter, ellipsoidal aggregates are seen oriented perpendicularly to the substrate. This result is confirmed by a combination of transmission and reflection FTIR measurements, which also point to lignin aggregates preferentially oriented perpendicularly to the substrate. For LB films from EL, on the other hand, aggregates are preferentially oriented parallel to the substrate, again consistent with the flat surface observed in AFM data. The vibrational spectroscopy data for cast films from both lignins show random molecular organization, as one should expect.