Determination of Cd(II) and Cd-metallothioneins in biological extracts using baker's yeast and inductively coupled plasma optical emission spectrometry

The use of Saccharomyces cerevisiae as a sorbent material to separate Cd(II) and Cd-metallothionein complex (Cd-MT) has been explored. Solid-liquid phase extractions were carried out in batch mode and the main parameters of the process (pH, temperature, time of incubation, amount of biomass and analyte) were evaluated. Under optimized conditions, the yeast quantitatively retain (94 +/- 5%) the Cd(II) while 97 +/- 2% of the Cd-MT remain in the supernatant. on base of the findings of this study, a simple method is proposed to determine Cd(II) and Cd-MT in cytosols extracted from mouse kidney and crab hepatopancreas. Inductively coupled plasma optical emission spectrometry was used to quantify the analytes in solid and liquid phase. Determination of Cd in the solid phase was carried out by introducing a slurry of the yeast (0.0625 g/10 mL) directly to the inductively coupled plasma optical emission spectrometer. Mixed standards solutions, which also have been submitted to the extraction procedure, were used to quantify the analytes in the samples. Thus, matrix effects due to nebulization of the slurry were overcame. Limits of detection (3 sigma) for Cd(II) and Cd-MT were 1.5 and 1.2 mu g L-1, respectively. Relative standard deviations of signals were 4.2% for measurements in the slurry of solid phase and 2.1% for measurements in the liquid phase. Recoveries of the analytes in cytosol samples were between 76 and 114%. The concentrations of Cd(II) (2.4 +/- 0.5 mu g L-1) and Cd-MT (3.0 +/- 0.5 mu g L-1) found by using the proposed approach were close to those found by tangential-flow ultrafiltration technique (2.6 +/- 0.7 mu g L-1 for Cd(II) and 3.7 +/- 1.7 mu g L-1 for Cd-MT).

Nonlinear optical properties of tungstate fluorophosphate glasses

The optical nonlinearity of tungstate fluorophosphate glasses, synthesized in the NaPO3-BaF2-WO3 system, was investigated through experiments based on the third-order susceptibility, chi((3)). Nonlinear (NL) refraction and NL absorption measurements in the picosecond regime were performed using the Z-scan technique at 532 nm. NL refractive index, n(2)proportional toRe chi((3)), ranging from 0.4x10(-14) cm(2)/W to 0.6x10(-14) cm(2)/W were determined. The two-photon absorption coefficient, alpha(2)proportional toIm chi((3)), for excitation at 532 nm, vary from 0.3 to 0.5 cm/GW. Light induced birefringence experiments performed in the femtosecond regime indicate that the response time of the nonlinearity at 800 nm is faster than 100 fs. The experiments show that chi((3)) is enhanced when the WO3 concentration increases and this behavior is attributed to the hyperpolarizabilities associated to W-O bonds. (C) 2004 American Institute of Physics.

Preparation, structural and optical characterization of BaWO4 and PbWO4 thin films prepared by a chemical route

Polycrystalline BaWO4 and PbWO4 thin films having a tetragonal scheelite structure were prepared at different temperatures. Soluble precursors such as barium carbonate, lead acetate trihydrate and tungstic acid, as starting materials, were mixed in aqueous solution. The thin films were deposited on silicon, platinum-coated silicon and quartz substrates by means of the spinning technique. The surface morphology and crystal structure of the thin films were investigated using scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction, and specular reflectance infrared Fourier transform spectroscopy, respectively. Nucleation stages and surface morphology evolution of thin films on silicon substrates have been studied by atomic force microscopy. XRD characterization of these films showed that BaWO4 and PbWO4 phase crystallize at 500 degreesC from an inorganic amorphous phase. FTIR spectra revealed the complete decomposition of the organic ligands at 500 degreesC and the appearance of two sharp and intense bands between 1000 and 600 cm(-1) assigned to vibrations of the antisymmetric stretches resulting from the high crystallinity of both thin films. The optical properties were also studied. It was found that BaWO4 and PbWO4 thin films have Eg = 5.78 eV and 4.20 eV, respectively, of a direct transition nature. The excellent microstructural quality and chemical homogeneity results confirmed that soft solution processing provides an inexpensive and environmentally friendly route for the preparation of BaWO4 and PbWO4 thin films. (C) 2003 Elsevier Ltd. All rights reserved.

Penetration of 38% hydrogen peroxide into the pulp chamber in bovine and human teeth submitted to office bleach technique

This study evaluated the pulp chamber penetration of peroxide bleaching agent in human and bovine teeth after office bleach technique. All the teeth were sectioned 3 mm apical of the cement-enamel junction and were divided into 2 groups, A (70 third human molars) and B (70 bovine lateral incisors), that were subdivided into A1 and B1 restored by using composite resin, A2 and B2 by using glass ionomer cement, and A3 and B3 by using resin-modified glass ionomer cement; A4, A5, B4, and B5 were not restored. Acetate buffer was placed in the pulp chamber, and the bleaching agent was applied for 40 minutes as follows: A1-A4 and B1-B4, 38% hydrogen peroxide exposure and A5 and B5, immersion into distilled water. The buffer solution was transferred to a glass tube in which leuco crystal violet and horseradish peroxidase were added, producing a blue solution. The optical density of the blue solution was determined by spectrophotometer and converted into microgram equivalents of hydrogen peroxide. Data were submitted to analysis of variance and Dunnett, Kruskal-Wallis, and Tukey tests (5%). A higher level of hydrogen peroxide penetrated into the pulp chamber in resin-modified glass ionomer cements in bovine (0.79 +/- 0.61 mu g) and human (2.27 +/- 0.41 mu g) groups. The bleaching agent penetration into the pulp chamber was higher in human teeth for any experimental situation. The penetration of the hydrogen peroxide depends on restorative materials, and under the conditions of this study human teeth are more susceptible to penetration of bleaching agent into the pulp chamber than bovine teeth.

Linear readout of dynamic phase modulation index in an optical voltage sensor using the new J(1) ... J(3) spectral method

The J(1)...J(3) is a recent optical method for linear readout of dynamic phase modulation index in homodyne interferometers. In this work, the J(1)... J(3) method is applied to measure voltage in an optical voltage sensor. Based on the classical J(1)...J(4) method, the J(1)... J(3) technique shows to be more stable to phase drift and simpler for implementation than the original one. The sensor dynamic range is enhanced. The agreement between theoretical and experimental results, based on 1/f noise, is demonstrated.

Femtosecond nonlinear optical properties of tellurite glasses

The third-order nonlinear optical properties of tellurite glasses with different compositions were investigated in the femtosecond regime at 810 nm. Using the I-scan technique, positive nonlinear refractive indices of similar to 10(-15) cm(2)/W were measured. The authors also determined that nonlinear absorption was negligible for all studied samples. This result, added to their good chemical stability, indicates that tellurite glasses are promising materials for ultrafast photonic applications. (c) 2006 American Institute of Physics.

The use of silica-immobilized brown alga (Pilayella littoralis) for metal preconcentration and determination by inductively coupled plasma optical emission spectrometry

The brown alga Pilayella littoralis was used as a new biosorbent in an on-line metal preconcentration procedure in a flow-injection system. Al, Co, Cu and Fe were determined in lake water samples by inductively coupled plasma optical emission spectrometry (ICP-OES) after preconcentration in a silica-immobilized alga column. Like other algae, P. littoralis exhibited strong affinity for these metals proving to be an effective accumulation medium. Metals were bound at pH 5.5 and were displaced at pH < 2 with diluted HCl. The enrichment factors for Cu-II, Fe-III, Al-III and Co-II were 13, 7, 16 and 11, respectively. Metal sorption efficiency ranged from 86 to 90%. The method accuracy was assessed by using drinking water certified reference material and graphite furnace atomic absorption spectrometry (GFAAS) as a comparison technique. The column procedure allowed a less time consuming, easy regeneration of the biomaterial and rigidity of the alga provided by its immobilization on silica gel. (C) 2003 Elsevier B.V. All rights reserved.

Effect of temperature on the optical properties of GaAsSbN/GaAs single quantum wells grown by molecular-beam epitaxy

GaAsSbN/GaAs strained-layer single quantum wells grown on a GaAs substrate by molecular-beam epitaxy with different N concentrations were studied using the photoluminescence (PL) technique in the temperature range from 9 to 296 K. A strong redshift in optical transition energies induced by a small increase in N concentration has been observed in the PL spectra. This effect can be explained by the interaction between a narrow resonant band formed by the N-localized states and the conduction band of the host semiconductor. Excitonic transitions in the quantum wells show a successive red/blue/redshift with increasing temperature in the 2-100 K range. The activation energies of nonradiative channels responsible for a strong thermal quenching are deduced from an Arrhenius plot of the integrated PL intensity. (C) 2003 American Institute of Physics.

Microstructural and optical characterization of CaWO4 and SrWO4 thin films prepared by a chemical solution method

Stoichiometric CaWO4 and SrWO4 thin films were synthesized using a chemical solution processing, the so-called polymeric precursor method. In this soft chemical method, soluble precursors such as strontium carbonate, calcium carbonate and tungstic acid, as starting materials, were mixed in an aqueous solution. The thin films were deposited on glass substrates by means of the spinning technique. The surface morphology and crystal structure of the thin films were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Nucleation stages and surface morphology evolution of the thin films on glass substrates were studied by atomic force microscopy. The films nucleate at 300 degreesC, after the coalescence of small nuclei into larger grains yielding a homogeneous dense surface. XRD characterization of these films showed that the CaWO4 and SrWO4 phases crystallize at 400 degreesC from an inorganic amorphous phase. No intermediate crystalline phase was identified. The optical properties were also studied. It was found that CaWO4 and SrWO4 thin films have an optical band gap, E-gap=5.27 and 5.78 eV, respectively, of a direct transition nature. The excellent microstructural quality and chemical homogeneity confirmed that this soft solution processing provides an inexpensive and environmentally friendly route for the preparation of CaWO4 and SrWO4 thin films. (C) 2003 Elsevier B.V. All rights reserved.

Synthesis, ferroelectric and optical properties of (Pb,Ca)TiO3 thin films by soft solution processing

Calcium modified lead titanate sol was synthesized using a soft solution processing, the so-called polymeric precursor method. In soft chemistry method, soluble precursors such as lead acetate trihydrate, calcium carbonate and titanium isopropoxide, as starting materials, were mixed in aqueous solution. Pb0.7Ca0.3TiO3 thin films were deposited on platinum-coated silicon and quartz substrates by means of the spinning technique. The surface morphology and crystal structure, dielectric and optical properties of the thin films were investigated. The electrical measurements were conducted on metal-ferroelectric-metal (MFM) capacitors. The typical measured small signal dielectric constant and dissipation factor at a frequency of 100 kHz were 299 and 0.065, respectively, for a thin film with 230 nm thickness annealed at 600degreesC for 2 h. The remanent polarization (2P(r)) and coercive field (E-c) were 32 muC/cm(2) and 100 kV/cm, respectively. Transmission spectra were recorded and from them, refractive index, extinction coefficient, and band gap energy were calculated. Thin films exhibited good optical transmissivity, and had optical direct transitions. The present study confirms the validity of the DiDomenico model for the interband transition, with a single electronic oscillator at 6.858 eV. The optical dispersion behavior of PCT thin film was found to fit well the Sellmeir dispersion equation. The band gap energy of the thin film, annealed at 600degreesC, was 3.56 eV. The results confirmed that soft solution processing provides an inexpensive and environmentally friendly route for the preparation of PCT thin films.

Active planar waveguides based on sol-gel Er3+-doped SiO2-ZrO2 for photonic applications: Morphological, structural and optical properties

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

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.

Speciation of lead in seawater and river water by using Saccharomyces cerevisiae immobilized in agarose gel as a binding agent in the diffusive gradients in thin films technique

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

Nonlinear optical properties of antimony-germanium-sulfur glasses at 1560 nm

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Influence of different solvents on the structural, optical and morphological properties of CdS nanoparticles

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