On-line redox speciation analysis of antimony using L-proline immobilized on controlled pore glass and hydride generation inductively coupled plasma optical emission spectrometry for detection

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

Luminescent nano-composites generated from a spray

The spray-pyrolysis (SP) synthesis technique has been employed to obtain SiO2:Eu3+ and gamma-AlOOH:Eu3+, It was possible to obtain sub-micrometric spherical particles of SiO2 with luminescent Eu3+ ions bonded to the silica surface or embedded in amorphous silica beads, by controlling the synthesis and annealing process. Boehmite y-AlOOH doped with Eu3+ nanoparticles were synthesized by SP at moderate temperature (200 degrees C) with Eu3+ ions bonded to the surface hydroxyls of the boehmite nanocrystals. Luminescent nanocomposites were obtained by controlled reaction of gamma-AlOOH:Eu3+ nanocrystals with ASN (asparagine). In these nano-composites, the Eu3+ are held at the surface of the boehmite nanocrystals and partially shielded from interactions with additional luminescence quenchers (hydroxyl groups, water molecules). (C) 2008 Elsevier B.V. All rights reserved.

Investigation of the pore blockage of a Brazilian dolomite during the sulfation reaction

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

The dimension of the pore space in sponges

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

Growth of silver nano-particle embedded in tellurite glass: Interaction between localized surface plasmon resonance and Er3+ ions

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

Pore size evolution during sintering of ceramic oxides

This paper reviews the influence of particle size distribution, agglomerates, rearrangement, sintering atmospheres and impurities on the pore evolution of some commonly studied oxides. These factors largely affect sintering mechanisms due to modifications of diffusion coefficients or evaporation-condensation. Very broad particle size distribution leads to grain growth and agglomerates densify first. Rearrangement of particles due to neck asymmetry mainly in the early stage of sintering is responsible for a high rate of densification in the first minutes of sintering by collapse of large pores. Sintering atmospheres play an important role in both densification and pore evolution. The chemical interaction of water molecules with several oxides like MgO, ZnO and SnO2 largely affects surface diffusion. As a consequence, there is an increase in the rates of pore growth and densification for MgO and ZnO and in the rate of pore growth for SnO2. Carbon dioxide does not affect the rate of sintering of MgO but greatly affects both rates of pore growth and densification of ZnO. Oxygen concentration in the atmosphere can especially affect semiconductor oxides but significantly affects the rate of pore growth of SnO2. Impurities like chlorine ions increase the rate of pore growth in MgO due to evaporation of HCl and Mg(OH)Cl, increasing the rate of densification and particle cuboidization. CuO promotes densification in SnO2, and is more effective in dry air. The rate of densification decrease and pore widening are promoted in argon. An inert atmosphere favors SnO2 evaporation due to reduction of CuO. © 1990.

Pore structure characterization of kaolin, metakaolin, and their acid-treated products using small-angle X-ray scattering

Pore structure of dealuminated kaolin and metakaolin was studied by small-angle X-ray scattering (SAXS). Both parent kaolin and metakaolin have about 10% of the total pore volume provided by globular pores with 105 Å mean pore size. Their surface area is about 14 m2/g. Acid dealumination of kaolin causes an increase of its globular pore volume without an appreciable change in the mean pore size, its surface area increasing up to about 90 m2/g. Acid dealumination of metakaolin enhances the globular pore volume, although there is generation of slit-shaped pores with a narrow thickness distribution whose mean value is 14 Å. This interlayer spacing causes an increase in surface area of about 190 m2/g by SAXS. © 1994.

β-galactosidase immobilization on controlled pore silica

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

Influence of viscoelastic characteristics of the colloidal suspensions on the formation of SnO2 supported membranes

SnO2 supported membranes have been prepared by sol-casting on alumina tubular substrate, using aqueous colloidal suspensions prepared by sol-gel route. The viscoelastic behaviour during sol ageing was analyzed by dinamic rheologial measurements. The complex viscosity and the storage and loss moduli have been followed during the sol-gel transition and the results have been correlated with the linear aggregates growth and the scalar percolation models. The scanning electron microscopy has evidenced that the homogeneity and thickness of the membrane depend on the sol ageing time. Crack-free and homogeneous membranes have been obtained for coated layers of 0.5μm thickness. © 1997 Trans Tech Publications.

On the specific filtration mechanism of a mesoporous silica membrane, prepared with non-connecting parallel pores

We report the singular filtration properties of an ultrafiltration membrane made with mesoporous silica that exhibits cylindrical pores aligned mostly normal to the support. This membrane supported on tubular commercial macroporous alumina supports was prepared by the interfacial growth mechanism between stable silica-surfactant hybrid micelles made of the association of silica oligomers with polyethyleneoxide-based (PEO) surfactants and sodium fluoride, a well-known silica condensation catalyst [Boissière et al., An ultrafiltration membrane made with mesoporous MSU-X silica, Chem. Mater. 15 (2003) 460-463]. It appears that the combined effect of the silica nature of the membrane, whose surface charge can be easily adjusted by changing the pH and the non-connected cylindrical shape of the pores provides a new behavior in the retention properties, as proved by the filtration of polyoxyethylene polymers (PEO) with different molecular weights. Depending on the filtration conditions, a rejection rate of 80% and a steep cut-off at 2000 Da can be obtained or, on the reverse, polymers three times bigger than the pore diameter can diffuse through the membrane. This new filtration mechanism, which opens up new modes of separation modes, is explained in the light of both topology of the porous network and pH-dependent interactions between PEO polymers and silica porous media. © 2004 Elsevier B.V. All rights reserved.

Early healing pattern of autogenous bone grafts with and without e-PTFE membranes: A histomorphometric study in rats

Objective. The aim of this study was to perform quantitative and qualitative analyses of the initial repair pattern of an autogenous bone block graft when covered or not with e-PTFE membranes. Study design. Sixty male Wistar rats received a bone graft plus an e-PTFE membrane (MB) or just the graft (B). A block graft was harvested from the animal's calvarium and was laid and stabilized on the external cortical area near the angle of the mandible. Descriptive histology and histomorphometric analyses were carried out and the data were analyzed statistically by ANOVA and the Tukey test, with the level of significance set at 5%. Results. The results for group B showed that there was bone loss during the healing period (B0 = 1.38, B45 = 1.05, F = 7.91 > F C = 3.02), that is, the initial volume of the graft decreased in time. Bone tissue loss was about 24%. In contrast, the MB group showed bone tissue gain along the observation period (MB0 = 1.54, MB45 = 2.40, F = 7.91 > FC = 3.02), meaning that the total volume of newly formed bone was greater than the original graft area. Bone tissue gain was approximately 55%. MB showed significantly greater bone gain when compared to B (B45 = 1.05, MB45 = 2.40, F = 39.86 > FC = 1.90). These significant differences between B and MB could already be observed after 21 days. Conclusions. The bone block graft underwent resorption at an early healing stage, while additional new bone formation was observed when the bone graft was covered with an e-PTFE membrane. © 2005 Mosby, Inc. All rights reserved.

Reconstruction of Mandibular Segmental Defects Using the Guided-Bone Regeneration Technique With Polylactide Membranes and/or Autogenous Bone Graft: A Preliminary Study on the Influence of Membrane Permeability

Purpose: Bone maintenance after mandibular reconstruction with autogenous iliac crest may be disappointing due to extensive resorption in the long term. The potential of the guided-bone regeneration (GBR) technique to enhance the healing process in segmental defects lacks comprehensive scientific documentation. This study aimed to investigate the influence of polylactide membrane permeability on the fate of iliac bone graft (BG) used to treat mandibular segmental defects. Materials and Methods: Unilateral 10-mm-wide segmental defects were created through the mandibles of 34 mongrel dogs. All defects were mechanically stabilized, and the animals were divided into 6 treatment groups: control, BG alone, microporous membrane (poly L/DL-lactide 80/20%) (Mi); Mi plus BG; microporous laser-perforated (15 cm2 ratio) membrane (Mip), and Mip plus BG. Calcein fluorochrome was injected intravenously at 3 months, and animal euthanasia was carried out at 6 months postoperatively. Results: Histomorphometry showed that BG protected by Mip was consistently related to larger amounts of bone compared with other groups (P ≤ .0001). No difference was found between defects treated with Mip alone and BG alone. Mi alone rendered the least bone area and reduced the amount of grafted bone to control levels. Data from bone labeling indicated that the bone formation process was incipient in the BG group at 3 months postoperatively regardless of whether or not it was covered by membrane. In contrast, GBR with Mip tended to enhance bone formation activity at 3 months. Conclusions: The use of Mip alone could be a useful alternative to BG. The combination of Mip membrane and BG efficiently delivered increased bone amounts in segmental defects compared with other treatment modalities. © 2008 American Association of Oral and Maxillofacial Surgeons.

Luminescent multifunctional biocellulose membranes

Luminescent biocellulose membranes were obtained by incorporation of ethanolic solutions of the europium compounds [Eu(BTFAC)3(H2O)2], [Eu(BTFA) 3(DBSO)2], [Eu(BTFA)3(PTSO)2] and [Eu(BTFA)3(FSO)2] (BTFAC- 4,4,4-Trifluoro-1- phenyl-1,3-butanedione DBSO- dibenzyl sulfoxide, PTSO- p-Tolyl sulfoxide and FSO- phenyl sulfoxide). Selfsustainable semi-transparent composite membranes were obtained showing strong emission under UV exctiation. The antenna hole played by the ligands was observed to be more efficient in the composite membranes than in the precursor complexes which by themselves are also strong red emitter compounds. These new multifuctional membranes could find application in different areas as phosphors and UV→Visible energy converting devices. © 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).

On a control design to an AFM microcantilever beam, operating in a tapping-mode, with irregular behavior

In last decades, control of nonlinear dynamic systems became an important and interesting problem studied by many authors, what results the appearance of lots of works about this subject in the scientific literature. In this paper, an Atomic Force Microscope micro cantilever operating in tapping mode was modeled, and its behavior was studied using bifurcation diagrams, phase portraits, time history, Poincare maps and Lyapunov exponents. Chaos was detected in an interval of time; those phenomena undermine the achievement of accurate images by the sample surface. In the mathematical model, periodic and chaotic motion was obtained by changing parameters. To control the chaotic behavior of the system were implemented two control techniques. The SDRE control (State Dependent Riccati Equation) and Time-delayed feedback control. Simulation results show the feasibility of the bothmethods, for chaos control of an AFM system. Copyright © 2011 by ASME.

Interface formation of nanostructured heterojunction SnO 2:Eu/GaAs and electronic transport properties

Thin films of tin dioxide (SnO2) are deposited by the sol-gel-dip-coating technique, along with GaAs layers, deposited by the resistive evaporation technique. The as-built heterojunction has potential application in optoelectronic devices, combining the emission from the rare-earth doped transparent oxide (Eu3+-doped SnO2 presents very efficient red emission) with a high mobility semiconductor. The advantage of this structure is the possibility of separation of the rare-earth emission centers from the electron scattering, leading to a strongly indicated combination for electroluminescence. Electrical characterization of the heterojunction SnO2:Eu/GaAs shows a significant conductivity increase when compared to the conductivity of the individual films, and the monochromatic light irradiation (266 nm) at low temperature of the heterojunction GaAs/SnO2:Eu leads to intense conductivity increase. Scanning electron microscopy (SEM) of the heterojunction cross section shows high adherence and good morphological quality of the interfaces substrate/SnO2 and SnO2/GaAs, even though the atomic force microscopy (AFM) image of the GaAs surface shows disordered particles, which increases with sample thickness. On the other hand, the good morphology of the SnO2:Eu surface, shown by AFM, assures the good electrical performance of the heterojunction. The observed improvement on the electrical transport properties is probably related to the formation of short conduction channels at the semiconductors interface, which may exhibit two-dimensional electron gas (2DEG) behavior. © 2012 Elsevier B.V. All rights reserved.