MEH-PPV hypsochromic shifts in halogenated solvents induced by gamma-rays

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Effect of TiO2 surface modification in Rhodamine B photodegradation

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

Photoluminescent behavior of BaWO4 powders processed in microwave-hydrothermal

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Chemical and spectroscopic studies of a new palladium(II) complex with N-acetyl-L-cysteine

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

Intense and broad photoluminescence at room temperature in structurally disordered Ba[Zr0.25Ti0.75]O-3 powders: An experimental/theoretical correlation

Intense and broad photoluminescence (PL) emission at room temperature was observed on structurally disordered Ba[Zr0.25Ti0.75]O-3 (BZT) powders synthesized by the polymeric precursor method. BZT powders were annealed at 573 K for different times and at 973 K for 2 h in oxygen atmosphere. The single-phase cubic perovskite structure of the powder annealed at 973 K for 2 It was identified by X-ray diffraction and Fourier transform Raman techniques. PL emission increased with the increase of annealing time, which reached its maximum value in the powder annealed at 573 K for 192 h. First principles quantum mechanical calculations based on density functional theory (B3LYP level) were employed to study the electronic structure of ordered and disordered models. The theoretical calculations and experimental measurements of Ultraviolet-visible absorption spectroscopy indicate that the presence of intermediary energy levels in the band gap is favorable for the intense and broad PL emission at room temperature in disordered BZT powders. The PL behavior is probably due the existence of a charge gradient on the disordered structure, denoted by means of a charge transfer process from [TiO5]-[ZrO6] or [TiO6]-[ZrO5] clusters to [TiO6]-[ZrO6] clusters. (C) 2008 Elsevier Ltd. All rights reserved.

Evaluation of the Possibility of Removing Staining by Repolishing Composite Resins Submitted to Artificial Aging

This in vitro research verified the possibility of eliminating staining caused by coffee and red wine in five composite resins, after being submitted to thermal cycling. Thirty-six specimens were prepared and immersed in water at 37 degrees C for 24 hours. After polishing, specimen color was measured in a spectrophotometer Cintra 10 UV (Visible Spectrometer, GBC, Braeside, VIC, Australia). All specimens were submitted to thermal cycling at temperatures of 5 and 55 degrees C with a dwell time of 1 minute, for 1,000 cycles in a 75% ethanol/water solution. After thermal cycling, the specimens were immersed in water at 37 degrees C until 7 days had elapsed from the time the specimens were prepared. All specimens were then taken to the spectrophotometer for color measurement. The specimens were divided into three groups (N = 12): distilled water (control), coffee, and red wine. For the staining process to occur on only one surface, all the sides, except one, of the surfaces were isolated with white wax. The specimens were immersed in one of the solutions at 37 degrees C for 14 days. The specimens were dried and taken to the spectrophotometer for color measurement. After this, the specimens were submitted to 20 mu m wear three times, and the color was measured after each one of the wear procedures. Calculation of the color difference was made using CIEDE2000 formula. According to the methodology used in this research, it was concluded that the staining caused by coffee and red wine was superficial and one wear of 20 mu m was sufficient to remove the discoloration.

Nanocomposites of Styrene-Butadiene Rubber and Synthetic Anatase Obtained by a Colloidal Route and Their Photooxidation

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

Generation of copper nanoparticles induced by fs-laser irradiation in borosilicate glass

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

Hydration-dependent conformational states of hemoglobin. Equilibrium and kinetic behavior

The equilibrium and kinetics of methemoglobin conversion to hemichrome induced by dehydration were investigated by visible absorption spectroscopy. Below about 0.20 g water per g hemoglobin only hemichrome was present in the sample; above this value, an increasing proportion of methemoglobin appeared with the increase in hydration. The transition between the two derivatives showed a time-dependent biphasic behavior and was observed to be reversible. The rates obtained for the transition of methemoglobin to hemichrome were 0.31 and 1.93 min-1 and for hemichrome to methemoglobin 0.05 and 0.47 min-1. We suggest that hemichrome is a reversible conformational state of hemoglobin and that the two rates observed for the transition between the two derivatives reflect the α- and β-chains of hemoglobin.

Synthesis, characterization and molecular structures of the pyridinium trans-bis(pyridine)tetrachlororuthenate(III) and pyridinium trans-(carbonyl)(pyridine)tetrachlororuthenate(III)

The pyH[trans-RuCl4(py)2](1) and pyH[trans-RuCl4(CO)(py)](2) complexes were synthesized and found to crystallize in space group P21/n, Z = 4 with a = 8.080(7), b = 22.503(7), c = 10.125(6) Å, β = 93.19(6)° for (1) and a = 7.821(1), b = 10.337(3), c = 19.763(3) Å, β = 93.07(1)° for (2). The structures were solved by Patterson and difference Fourier techniques and refined to R = 0.062 for (1) and R = 0.038 for (2). In both cases the Ru(III) ion is octahedrally coordinated to four co-planar chlorine atoms, the nitrogen of the pyridine rings or carbon from the carbon monoxide. Another protonated pyridine group, which forms the counter-cation completes the crystal structures. The UV-Vis absorption spectra show three bands: (1) 360 (ε = 1180 M-1 cm-1), 441 (ε = 3200 M-1 cm-1) and 532 nm (ε = 400 M-1 cm-1); (2) 315(ε = 1150 M-1 cm-1), 442 (ε = 3170 M-1 cm-1) and 530 nm (ε = 390 M-1 cm-1). The two higher energy bands were associated with ligand-to-metal charge transfer transitions and a third band at lower energy was assigned to a d-d transition. Low temperature EPR data confirmed the presence of the paramagnetically active Ru(III) and it is consistent with axial symmetry of the complexes. The position of the stretching CO band in complex (2) is discussed in terms of metal-CO backbonding.

Synthesis of manganese porphyrinosilica imprinted with templates using the sol-gel process

The optimized conditions for the preparation of a new manganese porphyrinosilica-template material are reported. The manganese porphyrinosilica-template was prepared by the sol-gel process, by the reaction of -SO2Cl groups present in the phenyl rings of MnTDC(SO2Cl)PPCl with 3-aminopropyltriethoxysilane. The reaction produces a precursor porphyrinopropylsilyl species, which were then polymerized with tetraethoxysilane. The presence of manganese porphyrin on xerogel is confirmed by ultraviolet visible absorption spectroscopy and thermogravimetric analysis (TGA). The prepared materials have surface areas between 19 and 674 m2 g-1. Electron spectroscopy imaging of the materials show that manganese distribution in the xerogel is uniform. Both manganese(III) porphyrinosilica-template and a similar iron(III) porphyrinosilica-template can catalyze the epoxidation of cyclooctene using iodozylbenzene as oxygen donor. The metalloporphyrinosilica-template presents catalytic activity similar to that of metaloporphyrin in solution. © 2000 Elsevier Science B.V. All rights reserved.

Room-temperature photoluminescence in amorphous SrTiO3-The influence of acceptor-type dopants

Room-temperature photoluminescence (PL) was observed in undoped and 2 mol% Cr-, Al- and Y-doped amorphous SrTiO3 thin films. Doping increased the PL, and in the case of Cr significantly reduced the associated PL wavelength. The optical bandgaps, calculated by means of UV-vis absorption spectra, increased with crystallinity and decreased with the doping level. It was considered that yttrium and aluminum substituted Sr2+, whereas chromium replaced Ti4+. It is believed that luminescence centers are oxygen-deficient BO6 complexes, or the same centers with some other defects, such as oxygen or strontium vacancies, or BO6 complexes with some other defects placed in their neighborhood. The character of excitation and the competition for negatively charged non-bridging oxygen (NBO) among numerous types of BO6 defect complexes in doped SrTiO3 results in various broadband luminescence peak positions. The results herein reported are an indicative that amorphous titanates are sensitive to doping, which is important for the control of the electro-optic properties of these materials. The probable incorporation of Cr into the Ti site suggests that the existence of a double network former can lead to materials displaying a more intense photoluminescence.

Antibiótico antifungico produzido por um estreptomiceto da região de Araraquara

With the significant increase in the incidence of invasive fungal infections during the last decade, mainly in patients with cancer, AIDS and other hospitalized patients who stay for long periods in intensive care units, there is an urgent need to screen for new antifungal agents possessing some advantages over known ones. This article reports a search in the field for a microorganism producing antibacterial and antifungal substances. Strains from soil samples collected in the region of Araraquara, Brazil, were isolated and analyzed for their antimicrobial potential against standard microorganisms (fungi Candida albicans and Aspergillus oryzae and bacteria Staphylococcus aureus and Escherichia coli). Out of the 64 strains isolated, 34 produced detectable antimicrobial activity. The streptomycete strain Ar4014 was chosen for further study, owing to its good antimicrobial activity against Candida albicans. Two of the fermentation media tested, 608-K and 602-B, were found to be best for the production and extraction of the antibiotic from Ar4014. After chromatographic separation of the crude extract on a silica column, the active fractions obtained showed UV-VIS absorption peaks characteristic of normal pentaenic antibiotics. The antibiotic was provisionally designated Ara 4014-75.

Effects of the biodegradation on biodegradable polymer blends and polypropylene

The large use of plastics in the world generates a large amount of waste which persists around 200 years in the environment. To minimize this effect is important to search some new polymer materials: the blends of biodegradable polymers with synthetic polymers. It is a large area that needs an Intensive research to investigate the blends properties and its behavior face to the different treatments to aim at the blodegradation. The blends used In this work are: some blodegradable polymers such as: poly(hydroxybutyrate) (PHB) and poly(s-polycaprolactone) (PCL) with a synthetic polymer, polypropylene (PP), in lower concentration. These blends were prepared using an internal mixer (Torque Rheometer), and pressed. These films were submitted to fungus biotreatment. The films analyses will be carried out by Fourier Transform Infrared (FTIR), UV-Vis absorption (UV-Vis), Scanning Electronic Microscopy (SEM), DSC and TGA. © 2008 American Institute of Physics.

Changes on transmittance mode of different composite resins

The purpose of this study was to evaluate the transmittance of seven different composite resins. Ten specimens were prepared (10 mm diameter, 2 mm thickness) for each experimental group, as follows: G1- Charisma® A 2 (Heraeus-Kulzer); G2- Filtek™ Supreme A 2E (3M/ESPE); G3- Filtek™ Supreme A2B (3M/ESPE); G4-Filtek™ Supreme YT (3M/ESPE); G5- Esthet-X® A2 (Dentsply); G6- Esthet-X® YE (Dentsply); G7- Durafill® A 2 (Heraeus-Kulzer) and G8- Filtek™ Z-100 A2 (3M/ESPE). The transmittance mode was measured using a UV-visible spectrophotometer (Cary Instruments) at 400-760 nm. The specimens were evaluated at three different times: zero hour (initial), 24 hours and 10 days after immersion in artificial saliva. The differences in transmittance were determined by two-way analysis of variance (ANOVA) and Tukey's test. The various composite resins showed significant differences in the wavelength dependence of transmittance. The mean values of transmittance increased significantly, with wavelengths increasing from 400 to 760 nm. The performance of the experimental groups was similar in terms of immersion time, considering that at time zero and after 10 days, all the groups showed similar results, which were statistically higher than the values obtained after 24 hours of immersion. The Filtek™ Supreme YT composite resin presented the highest mean transmittance values along the wavelengths at the three measured times. Esthet-X® YE and Durafill® yielded similar mean transmittance values, which were higher than those of the other groups. This study shows that the transmittance values of composite resins are directly related with the type, size and amount of inorganic filler particles.