Influence of the Solvent Evaporation Rate on the Crystalline Phases of Solution-Cast Poly(Vinylidene Fluoride) Films

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Photo-electrochemical investigation of anodic oxide films on cast Ti-Mo alloys I. Anodic behaviour and effect of alloy composition

The anodic behaviour of cast Ti-Mo alloys, having different Mo contents (6-20 wt.%), was investigated in acidic and neutral aerated aqueous solutions. All sample showed a valve-metal behaviour, owing to formation and thickening of barrier-type anodic oxides displaying interference colours Growth kinetics. of passive films is influenced by both anodizing electrolyte and composition of the starting alloy. This last parameter was found to change also the solid-state properties of the films, explored by photoelectrochemical and impedance spectroscopy experiments. Thicker films (U(f) = 8 V/MSE) grown on alloys richer in Mo showed more resistive character and a photocurrent sign inversion under negative bias, that revealed an insulating character, whereas corresponding films grown on alloys with lower Mo content, as well as thinner films, behaved as n-type semiconductors. Results are discussed in terms of formation of a mixed Ti-Mo oxide phase. (C) 2008 Elsevier Ltd. All rights reserved

The influence of soil and landfill leachate microorganisms in the degradation of PVC/PCL films cast from DMF

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

Nanostructured hybrid films containing nanophosphor: Fabrication and electronic spectral properties

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

Portable smart films for ultrasensitive detection and chemical analysis using SERS and SERRS

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

Carbon dioxide formation during initial stages of photodegradation of poly(ethyleneterephthalate) (PET) films

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

Al-based anodic oxide films structure observation using field emission gun scanning electron microscopy

In the present work, the anodic oxide films of Al, Al-Cu 4.5% and Al-Si 6.5% alloys are formed using direct and pulse current. In the case of Al-Cu and Al-Si alloys, the electrolyte used contains sulfuric acid and oxalic acid, meanwhile for Al the electrolyte contains sulfuric acid only. Al-Cu alloy was submitted to a heat treatment in order to decrease the effect of inter metallic phase theta upon the anodic film structure. Fractured samples were observed using a field emission gun scanning electron microscope JSM-6330F at (LME)/Brazilian Synchrotron Light Laboratory (LNLS), Campinas, SP, Brazil. The oxide film images enable evaluation of the pore size and form with a resolution similar to the transmission electron microscope (TEM) resolution. It is also observed that the anodizing process using pulse current produces an irregular structure of pore walls, and by direct cur-rent it is produced a rectilinear pore wall. (c) 2005 Elsevier B.V. All rights reserved.

Evaluation of the Genotoxicity of Chitosan Nanoparticles for Use in Food Packaging Films

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

Ascorbate electro-oxidation by modified electrodes: Polypyrrole and polypyrrole/Ni(OH)(2) composite thin films

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Dependence of the electrical conductivity and elastomeric properties on sample preparation of blends of polyaniline and natural rubber

Blend films (free-standing) containing 20% in volume of polyaniline (PANI) in 80% of natural rubber (NR) were fabricated by casting in three different ways: (1) adding PANI-EB (emeraldine base) dissolved in N-methyl-2-pyrrolidone (NMP) to the latex (NRL), (2) adding PANI-EB dissolved in in-cresol to NR dissolved in xylol (NRD), (3) overlaying the surface of a pure NR cast film with a PANI layer grown by in situ polymerization (NRO). All the films were immersed into HCl solution to achieve the primary doping (protonation) of PANI before the characterization. The main goal here was to investigate the elastomeric and electrical conductivity properties for each blend, which may be applied as pressure and deformation sensors in the future. The characterization was carried out by optical microscopy, dc conductivity, vibrational spectroscopy (infrared absorption and Raman scattering), thermogravimetry analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), and tensile stress-strain curves. The results suggest that the NRL blend is the most suitable in terms of mechanical and electrical properties required for applications in pressure and deformation sensors: a gain of conductivity without losing the elastomeric property of the rubber. (c) 2005 Wiley Periodicals, Inc.

Wine classification by taste sensors made from ultra-thin films and using neural networks

This paper reports on a sensor array able to distinguish tastes and used to classify red wines. The array comprises sensing units made from Langmuir-Blodgett (LB) films of conducting polymers and lipids and layer-by-layer (LBL) films from chitosan deposited onto gold interdigitated electrodes. Using impedance spectroscopy as the principle of detection, we show that distinct clusters can be identified in principal component analysis (PCA) plots for six types of red wine. Distinction can be made with regard to vintage, vineyard and brands of the red wine. Furthermore, if the data are treated with artificial neural networks (ANNs), this artificial tongue can identify wine samples stored under different conditions. This is illustrated by considering 900 wine samples, obtained with 30 measurements for each of the five bottles of the six wines, which could be recognised with 100% accuracy using the algorithms Standard Backpropagation and Backpropagation momentum in the ANNs. (C) 2003 Elsevier B.V. All rights reserved.

Immobilization of uricase in layer-by-layer films used in amperometric biosensors for uric acid

The layer-by-layer technique was exploited to immobilize the enzyme uricase onto indium tin oxide substrates coated with a layer of Prussian Blue. Uricase layers were alternated with either poly(ethylene imine) or poly(diallyidimethylammoniumchloride), and the resulting films were used as amperometric biosensors for uric acid. Biosensors with optimum perfomance had a limit of detection of 0.15 mu A mu mol 1(-1) cm(-2) with a linear response between 0.1 and 0.6 mu M of uric acid, which is sufficient for use in clinical tests. Bioactivity was preserved for weeks, and there was negligible influence from interferents, as detection was carried out at 0.0 V vs saturated calomel electrode.

Surface-enhanced Raman scattering and micro-Raman imaging of Langmuir-Blodgett films of rhodium phthalocyanine

Rhodium phthalocyanine (RhPc) was synthesized and ultra thin Langmuir-Blodgett (LB) films of RhPc were successfully fabricated. The LB film characterization was carried out using both UV-vis absorption spectra and Raman scattering. The Raman spectroscopy was carried out using 633 and 780 nm laser lines. LB films were deposited onto Ag nanoparticles to achieve the surface-enhanced pre-resonance Raman scattering (pre-SERRS) and surface-enhanced Raman scattering (SERS) for both laser lines, respectively, which allowed the characterization of the RhPc ultra thin films. The morphology of the LB RhPc neat film is extracted from micro-Raman imaging. (C) 2003 Elsevier B.V. All rights reserved.

Langmuir and Langmuir-Blodgett (LB) films of poly [(2-methoxy,5-n-octadecyl)-p-phenylenevinylene] (OC1OC18-PPV)

A PPV derivative, poly(2-methoxy,5-(n-octadecyl)-p-phenylenevinylene) (OC1OC18-PPV), has been synthesized via the Gilch route and used to fabricate Langmuir and Langmuir-Blodgett (LB) films. True monomolecular films were formed at the air/water interface, which were successfully transferred onto different types of substrate. Using UV-visible absorption, FTIR, fluorescence and Raman scattering spectroscopies we observed that the polymer molecules were randomly distributed in the LB film, with no detectable anisotropy. This is in contrast to the anisotropic LB films of a previously reported PPV derivative, poly(2-methoxy-5-n-hexyloxy)-p-phenylenevinylene (OC1OC6-PPV), which is surprising because the longer chain of OC1OC18-PPV investigated here was expected to lead to more ordered films. As a consequence of the lack of order, LB films of OC1OC18-PPV exhibit lower photoconductivity and require higher operating voltage in a polymer light-emitting diode (PLED) in comparison with LB films of OC1OC6-PPV. This result confirms the importance of molecular organization in the LB film to obtain efficient PLEDs. (c) 2005 Elsevier Ltd. All rights reserved.

Layer by layer TiO2 thin films and photodegradation of Congo red

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)