Composição fenólica das partes comestíveis das uvas BRS Carmem e BRS Magna

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Long range resonance energy transfer from a dye molecule to graphene has (distance)-4 dependence

In our previous report on resonance energy transfer from a dye molecule to graphene [J. Chem. Phys.129, 054703 (2008)], we had derived an expression for the rate of energy transfer from a dye to graphene. An integral in the expression for the rate was evaluated approximately. We found a Yuwaka-type dependence of the rate on the distance. We now present an exact evaluation of the integral involved, leading to very interesting results. For short distances (z < 20 A), the present rate and the previous rate are in good agreement. For larger distances, the rate is found to have a z(-4) dependence on the distance, exactly. Thus we predict that for the case of pyrene on graphene, it is possible to observe fluorescence quenching up to a distance of 300 A. This is in sharp contrast to the traditional fluorescence resonance energy transfer where the quenching is observable only up to 100 A.

Characteristics of Photo Electrodes Based on TiO2 Nanoparticles, Nanotubes and Microspheres for Dye Solar Cell

We have analyzed the characteristics of electrodes made of TiO2 nanotubes, microspheres and commercially available nanoparticles for dye sensitized solar cell. The morphology of the electrodes and the formation of aggregates have been analyzed by scanning electron microscopy and surface profiling technique. The concentration of Ti3+ type impurity state on the surface of these electrodes is quantified by X-ray photoelectron spectroscopy. Micro structural properties have been characterized by Brunauer, Emmett and Teller method The optical properties of the electrodes such as band gap energy, the type of band formation and the diffuse reflectance are evaluated by UV-Visible spectroscopy. The photovoltaic characteristics of dye solar cell made of these electrodes have been evaluated and it is found that the characteristics of the TiO2 film alone can alter the overall conversion efficiency to a great extent. Additional analysis using electrochemical impedance spectroscopy has been carried out to probe the electron transport properties and charge collection efficiency of these electrodes.

Scheelite-type MWO4 (M = Ca, Sr, and Ba) nanophosphors: Facile synthesis, structural characterization, photoluminescence, and photocatalytic properties

Scheelite-type MWO4 (M = Ca, Sr, and Ba) nanophosphors were synthesized by the precipitation method. All compounds crystallized in the tetragonal structure with space group 141/a (No. 88). Scherrer's and TEM results revealed that the average crystallite size varies from 32 to 55 nm. FE-SEM illustrate the spherical (CaWO4), bouquet (SrWO4), and fish (BaWO4) like morphologies. PL spectra indicate the broad emission peak maximum at 436 (CaWO4), 440 (SrWO4), and 433 nm (BaWO4) under UV excitation. The calculated CIE color coordinates of MWO4 nanophosphors are close to the commercial BAM and National Television System Committee blue phosphor. The photocatalytic activities of MWO4 were investigated for the degradation of methylene blue dye under UV illumination. At pH 3, BaWO4 nanocatalyst showed 100% dye degradation within 60 min. The photocatalytic activity was in the decreasing order of BaWO4> CaWO4>SrWO4 under both neutral and acidic conditions. (C) 2014 Elsevier Ltd. All rights reserved.

Measurement of two-photon excitation cross-section of a new symmetric-type fluorene derivative

A new dye, 2,7-bis(4-methoxystyryl)-9,9-bis(2-ethylhexyl)-9H-fluorene, has been synthesized, which is a D-pi-D symmetrical-type fluorene derivative. The two-photon absorption (TPA) of this new dye has been experimentally studied by comparable two-photon-induced fluorescence method. This new dye has a TPA cross-section of 84 x 10(-50) cm(4) s/photon at 790 nm/13 fs. (c) 2004 Elsevier GmbH. All rights reserved.

Dynamic storage performance of two cyanine dye films and optimization design for a recordable compact disk

The optical constants of two cyanine dye films that we prepared were measured with a RAP-1-type (RAP is rotating analyzer and polarizer) spectroscopic ellipsometer. Toward making a simplified model for the wafers of a recordable compact disk (CD-R), we give their optimization designs developed with the cyanine dye films. in addition, the dynamic storage performances of two sample disks were tested by our dynamic storage testing system. Measurement results of the sample disks were obtained to test and verify our film designs. (C) 2000 Optical Society of America. OCIS codes: 160.4890, 160.4760, 210.4810.

Preparation, characterization and luminescent properties of MCM-41 type materials impregnated with rare earth complex

Hybrid materials incorporating Eu-(TTA)(3). 2H(2)O (7hereafter designated as Eu-TTA, with TTA: thenoyltrifluoroacetone) in unmodified or modified MCM-41 by 3-aminopropyl-triethoxysilane (APTES) were prepared by impregnation method. The obtained materials were characterized using X-ray diffraction (XRD), IR and diffuse reflectance spectroscopy and luminescence spectra. All the hybrid samples exhibited the characteristic emission bands of EU3+ under UV light excitation at room temperature, and the excitation spectra showed significant blue-shifts compared to the pure rare-earth complex. Although the red emission intensity in the modified hybrid was almost the half of the red emission intensity in the pure Eu-TTA complex at room temperature, the hybrid showed a much higher thermal stability due to the shielding character of the MCM-41 host.

Mechanisms and chemistry of dye adsorption on manganese oxides-modified diatomite

The investigations into structural changes which occur during adsorbent modification and the adsorption mechanisms are essential for an effective design of adsorption systems. Manganese oxides were impregnated onto diatomite to form the type known as delta-birnessite. Initial investigations established the effectiveness of manganese oxides-modified diatomite (MOMD) to remove basic and reactive dyes from aqueous solution. The adsorption capacity of MOMD for methylene blue (MB), hydrolysed reactive black (RB) and hydrolysed reactive yellow (RY) was 320, 419, and 204 mg/g, respectively. Various analytical techniques were used to characterise the structure and the mechanisms of the dye adsorption process onto MOMD such as Fourier transform infrared (FTIR), X-ray diffraction (XRD) and atomic absorption spectrometry (A.A.). A small shift to higher values of the cl-spacing of dye/MOMD was observed indicating that a small amount of the dye molecules were intercalated in the MOMD structure and other molecules were adsorbed on the external surface of MOMD. Two mechanisms of dye adsorption onto MOMD were proposed; intercalation of the dye in the octahedral layers and adsorption of the dye on the MOMD external surface. Moreover, the results demonstrated that the MOMD structure was changed upon insertion of MB and RY with an obvious decrease in the intensity of the second main peak of the MOMD X-ray pattern. (C) 2009 Elsevier Ltd. All rights reserved.

MODELED DIFFUSION-CONTROLLED RESPONSE AND RECOVERY BEHAVIOR OF A NAKED OPTICAL FILM SENSOR WITH A HYPERBOLIC-TYPE RESPONSE TO ANALYTE CONCENTRATION

The diffusion-controlled response and recovery behaviour of a naked optical film sensor (i.e., with no protective membrane) with a hyperbolic-type response [i.e., S0/S = (1 + Kc), where S is the measured value of the absorbance or luminescence intensity of one form of the sensor dye in the presence of the analyte, S0 is the observed value of S in the absence of analyte and K is a constant] to changes in analyte concentration, c, in a system under test is approximated using a simple model, and described more accurately using a numerical model; in both models it is assumed that the system under test represents an infinite reservoir. Each model predicts the variations in the response and recovery times of such an optical sensor, as a function of the final external analyte concentration, the film thickness (I) and the analyte diffusion coefficient (D). From an observed signal versus time profile for a naked optical film sensor it is shown how values for K and D/I2 can be extracted using the numerical model. Both models provide a qualitative description of the often cited asymmetric nature of the response and recovery for hyperbolic-type response naked optical film sensors. It is envisaged that the models will help in the interpretation of the response and recovery behaviour exhibited by many naked optical film sensors and might be especially apposite when the analyte is a gas.

Fabrication and Characterization of Dye Sensitized Polymer Films for Holographic Applications

Holographic technology is at the dawn of quick evolution in various new areas including holographic data storage, holographic optical elements, artificial intelligence, optical interconnects, optical correlators, commerce, medical practice, holographic weapon sight, night vision goggles and games etc. One of the major obstacles for the success of holographic technology to a large extent is the lack of suitable recording medium. Compared with other holographic materials such as dichromated gelatin and silver halide emulsions, photopolymers have the great advantage of recording and reading holograms in real time and the spectral sensitivity could be easily shifted to the type of recording laser used by simply changing the sensitizing dye. Also these materials possess characteristics such as good light sensitivity, real time image development, large dynamic range, good optical properties, format flexibility, and low cost. This thesis describes the attempts made to fabricate highly economic photopolymer films for various holographic applications. In the present work, Poly (vinyl alcohol) (PVA) and poly (vinyl chloride) (PVC) are selected as the host polymer matrices and methylene blue (MB) is used as the photosensitizing dye. The films were fabricated using gravity settling method. No chemical treatment or pre/post exposures were applied to the films. As the outcome of the work, photopolymer films with more than 70% efficiency, a permanent recording material which required no fixing process, a reusable recording material etc. were fabricated.

A comparative study of energy transfer in dye mixtures in monomer and polymer matrices under pulsed laser excitation

This study was conducted to identify the concentration dependence of the operating wavelengths and the relative intensities in which a dye mixture doped polymer optical fibre can operate. A comparative study of the radiative and Forster type energy transfer processes in Coumarin 540:Rhodamine 6G, Coumarin 540:Rhodamine B and Rhodamine 6G:Rhodamine B in methyl methacrylate (MMA) and poly(methyl methacrylate) (PMMA) was done by fabricating a series of dye mixture doped polymer rods which have two emission peaks with varying relative intensities. These rods can be used as preforms for the fabrication of polymer optical fibre amplifiers operating in the multi-wavelength regime. The 445 nm line from an Nd:YAG pumped optical parametric oscillator (OPO) was used as the excitation source for the first two dye pairs and a frequency doubled Nd:YAG laser emitting at 532 nm was used to excite the Rh 6G:Rh B pair. The fluorescence lifetimes of the donor molecule in pure form as well as in the mixtures were experimentally measured in both monomer and polymer matrices by time-correlated single photon counting technique. The energy transfer rate constants and transfer efficiencies were calculated and their dependence on the acceptor concentration was analysed. It was found that radiative energy transfer mechanisms are more efficient in all the three dye pairs in liquid and solid matrices.

Type 2 diabetes and impaired glucose tolerance are associated with word memory source monitoring recollection deficits but not simple recognition familiarity deficits following water, low glycaemic load, and high glycaemic load breakfasts.

Isolated source monitoring recollection deficits indicate that abnormalities in glucose metabolism are not detrimental for global episodic memory processes. This enhances our understanding of how metabolic disorders are associated with memory impairments.

Acute glycaemic load breakfast manipulations do not attenuate cognitive impairments in adults with type 2 diabetes

Abnormalities in glucose tolerance such as type 2 diabetes can have demonstrable negative effects on a range of cognitive functions. However, there was no evidence that low GL breakfasts administered acutely could confer benefits for cognitive function (ClincalTrials.gov identifier, NCT01047813).