Infrared emissions, visible up-conversion, thermoluminescence and defect centres in Er(3)Al(5)O(12) phosphor obtained by solution combustion reaction

The Er(3)Al(5)O(12) phosphor powders were prepared using the solution combustion method. Formation and homogeneity of the Er(3)Al(5)O(12) phosphor powders have been verified by X-ray diffraction and energy-dispersive X-ray analysis respectively. The frequency up-conversion from Er(3)Al(5)O(12) phosphor powder corresponding to the (2)H(9/2) -> (4)I(15/2), (2)H(11/2) -> (4)I(15/2), (4)S(3/2) -> (4)I(15/2), (4)F(9/2) -> (4)I(15/2) and the infrared emission (IR) due to the (4)I(13/2) -> (4)I(15/2) transitions lying at similar to 410, similar to 524, similar to 556, 645-680 nm and at similar to 1.53 mu m respectively upon excitation with a Ti-Sapphire pulsed/CW laser have been reported. The mechanism responsible for the frequency up-conversion and IR emission is discussed in detail. Defect centres induced by radiation were studied using the techniques of thermoluminescence and electron spin resonance. A single glow peak at 430A degrees C is observed and the thermoluminescence results show the presence of a defect center which decays at high temperature. Electron spin resonance studies indicate a center characterized by a g-factor equal to 2.0056 and it is observed that this center is not related to the thermoluminescence peak. A negligibly small concentration of cation and anion vacancies appears to be present in the phosphor in accordance with the earlier theoretical predictions.

Obtenção e caracterização de dióxido de estanho nanoestruturado pelo método de síntese contínua por combustão em solução

Continuous Synthesis by Solution Combustion was employed in this work aiming to obtain tin dioxide nanostructured. Basically, a precursor solution is prepared and then be atomized and sprayed into the flame, where its combustion occurs, leading to the formation of particles. This is a recent technique that shows an enormous potential in oxides deposition, mainly by the low cost of equipment and precursors employed. The tin dioxide (SnO2) nanostructured has been widely used in various applications, especially as gas sensors and varistors. In the case of sensors based on semiconducting ceramics, where surface reactions are responsible for the detection of gases, the importance of surface area and particle size is even greater. The preference for a nanostructured material is based on its significant increase in surface area compared to conventional microcrystalline powders and small particle size, which may benefit certain properties such as high electrical conductivity, high thermal stability, mechanical and chemical. In this work, were employed as precursor solution tin chloride dehydrate diluted in anhydrous ethyl alcohol. Were utilized molar ratio chloride/solvent of 0,75 with the purpose of investigate its influence in the microstructure of produced powder. The solution precursor flux was 3 mL/min. Analysis with X-ray diffraction appointed that a solution precursor with molar ratio chloride/solvent of 0,75 leads to crystalline powder with single phase and all peaks are attributed to phase SnO2. Parameters as distance from the flame with atomizer distance from the capture system with the pilot, molar ratio and solution flux doesn t affect the presence of tin dioxide in the produced powder. In the characterization of the obtained powder techniques were used as thermogravimetric (TGA) and thermodiferential analysis (DTA), particle size by laser diffraction (GDL), crystallographic analysis by X-ray diffraction (XRD), morphology by scanning electron microscopy (SEM), transmission electron microscopy (TEM), specific surface area (BET) and electrical conductivity analysis. The techniques used revealed that the SnO2 exhibits behavior of a semiconductor material, and a potentially promising material for application as varistor and sensor systems for gas

Obtenção e caracterização de dióxido de estanho nanoestruturado pelo método de síntese contínua por combustão em solução

Continuous Synthesis by Solution Combustion was employed in this work aiming to obtain tin dioxide nanostructured. Basically, a precursor solution is prepared and then be atomized and sprayed into the flame, where its combustion occurs, leading to the formation of particles. This is a recent technique that shows an enormous potential in oxides deposition, mainly by the low cost of equipment and precursors employed. The tin dioxide (SnO2) nanostructured has been widely used in various applications, especially as gas sensors and varistors. In the case of sensors based on semiconducting ceramics, where surface reactions are responsible for the detection of gases, the importance of surface area and particle size is even greater. The preference for a nanostructured material is based on its significant increase in surface area compared to conventional microcrystalline powders and small particle size, which may benefit certain properties such as high electrical conductivity, high thermal stability, mechanical and chemical. In this work, were employed as precursor solution tin chloride dehydrate diluted in anhydrous ethyl alcohol. Were utilized molar ratio chloride/solvent of 0,75 with the purpose of investigate its influence in the microstructure of produced powder. The solution precursor flux was 3 mL/min. Analysis with X-ray diffraction appointed that a solution precursor with molar ratio chloride/solvent of 0,75 leads to crystalline powder with single phase and all peaks are attributed to phase SnO2. Parameters as distance from the flame with atomizer distance from the capture system with the pilot, molar ratio and solution flux doesn t affect the presence of tin dioxide in the produced powder. In the characterization of the obtained powder techniques were used as thermogravimetric (TGA) and thermodiferential analysis (DTA), particle size by laser diffraction (GDL), crystallographic analysis by X-ray diffraction (XRD), morphology by scanning electron microscopy (SEM), transmission electron microscopy (TEM), specific surface area (BET) and electrical conductivity analysis. The techniques used revealed that the SnO2 exhibits behavior of a semiconductor material, and a potentially promising material for application as varistor and sensor systems for gas

Photoelectroactivity of Bismuth Vanadate Prepared by Combustion Synthesis: Effect of Different Fuels and Surfactants

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Synthesis, characterisation, luminescence and defect centres in solution combustion synthesised CaZrO3:Tb3+ phosphor

Tb3+ doped CaZrO3 has been prepared by an easy solution combustion synthesis method. The combustion derived powder was investigated by X-ray diffraction, Fourier-transform infrared spectrometry and scanning electron microscopy techniques. A room temperature photoluminescence study showed that the phosphors can be efficiently excited by 251 nm light with a weak emission in the blue and orange region and a strong emission in green light region. CaZrO3:Tb3+ exhibits three thermoluminescence (TL) glow peaks at 126 degrees C, 200 degrees C and 480 degrees C. Electron Spin Resonance (ESR) studies were carried out to study the defect centres induced in the phosphor by gamma irradiation and also to identify the centres responsible for the TL peaks. The room temperature ESR spectrum of irradiated phosphor appears to be a superposition of two distinct centres. One of the centres (centre I) with principal g-value 2.0233 is identified as an O- ion. Centre II with an axial symmetric g-tensor with principal values g(parallel to) = 1.9986 and g(perpendicular to) = 2.0023 is assigned to an F+ centre (singly ionised oxygen vacancy). An additional defect centre is observed during thermal annealing experiments and this centre (assigned to F+ centre) seems to originate from an F centre (oxygen vacancy with two electrons). The F centre and also the F+ centre appear to correlate with the observed high temperature TL peak in CaZrO3:Tb3+ phosphor. (c) 2012 Elsevier B.V. All rights reserved.

Preparation and characterization of nanosized SrBi2Nb2O9 powder by the combustion synthesis

This work presents the preparation of SrBi2Nb2O9 (SBN) directly by the combustion synthesis. Strontium nitrate, niobium ammonium oxalate (NH4H2[NbO-(C2O4)(3)].3H(2)O) and bismuth oxide were used as oxidant reactants and urea as fuel. The influence of the fuel was evaluated by the addition of different fuel amounts (50%, 100%, 200% and 300%), 100% being the stoichiometric proportion. The XRD patterns showed that the SBN perovskite crystallized as the majority phase. The as-synthesized stoichiometric powder presented a specific surface area of around 13 m(2)/g and a mean grain size of around 16 nm. Dilatometric measurements showed that the maximum sintering rate occurs at 1275degreesC. The determination of the ferroparaelectric transition showed a Curie temperature (T-c) of 429degreesC. (C) 2002 Elsevier B.V. B.V. All rights reserved.

Scale Up of PLA Nanoparticle Synthesis by Solvent Displacement and Functionalization of the Particles with a Silica Shell for Targeted Drug Delivery Applications

Biodegradable polymer nanoparticles have the properties necessary to address many of the issues associated with current drug delivery techniques including targeted and controlled delivery. A novel drug delivery vehicle is proposed consisting of a poly(lactic acid) nanoparticle core, with a functionalized, mesoporous silica shell. In this study, the production of PLA nanoparticles is investigated using solvent displacement in both a batch and continuous manner, and the effects of various system parameters are examined. Using Pluronic F-127 as the stabilization agent throughout the study, PLA nanoparticles are produced through solvent displacement with diameters ranging from 200 to 250 nm using two different methods: dropwise addition and in an impinging jet mixer. The impinging jet mixer allows for easy scale-up of particle production. The concentration of surfactant and volume of quench solution is found to have minimal impact on particle diameter; however, the concentration of PLA is found to significantly impact the diameter mean and polydispersity. In addition, the stability of the PLA nanoparticles is observed to increase as residual THF is evaporated. Lastly, the isolated PLA nanoparticles are coated with a silica shell using the Stöber Process. It is found that functionalizing the silica with a phosphonic silane in the presence of excess Pluronic F-127 decreases coalescence of the particles during the coating process. Future work should be conducted to fine-tune the PLA nanoparticle synthesis process by understanding the effect of other system parameters and in synthesizing mesoporous silica shells.

Continuous nitric oxide synthesis by inducible nitric oxide synthase in normal human airway epithelium in vivo.

Nitric oxide (NO) is an important mediator of inflammatory responses in the lung and a key regulator of bronchomotor tone. An airway NO synthase (NOS; EC 1.14.13.39) has been proposed as a source of endogenous NO in the lung but has not been clearly defined. Through molecular cloning, we conclusively demonstrate that NO synthesis in normal human airways is due to the continuous expression of the inducible NOS (iNOS) isoform in airway epithelial cells. Although iNOS mRNA expression is abundant in airway epithelial cells, expression is not detected in other pulmonary cell types, indicating that airway epithelial cells are unique in the continuous pattern of iNOS expression in the lung. In situ analysis reveals all airway epithelial cell types express iNOS. However, removal of epithelial cells from the in vivo airway environment leads to rapid loss of iNOS expression, which suggests expression is dependent upon conditions and/or factors present in the airway. Quantitation of NOS activity in epithelial cell lysates indicates nanomolar levels of NO synthesis occur in vivo. Remarkably, the high-level iNOS expression is constant in airway epithelium of normal individuals over time. However, expression is strikingly decreased by inhaled corticosteroids and beta-adrenergic agonists, medications commonly used in treatment of inflammatory airway diseases. Based upon these findings, we propose that respiratory epithelial cells are key inflammatory cells in the airway, functioning in host defense and potentially playing a role in airway inflammation.

Synthesis, structure, solution chemistry and the electronic effect of para substituents on the vanadium center in a family of mixed-ligand [(VO)-O-V(ONO)(ON)] compexes

Four tridentate dibasic ONO donor hydrazone ligands derived from the condensation of benzoylhydrazine with either 2-hydroxyacetophenone or its para substituted derivatives (H2L1-4, general abbreviation H2L) have been used as primary ligands and 8-hydroxyquinoline (Hhq, a bidentate monobasic ON donor species) has been used as auxiliary ligand. The reaction of [(VO)-O-IV(acac)21 with H2L in methanol followed by the addition of Hhq in equimolar ratio under aerobic condition afforded the mixed-ligand oxovanadium(V) complexes of the type [(VO)-O-V(L)(hq)] (1-4) in excellent yield. The X-ray structure of the compound [(VO)-O-V(L-4)(hq)] (4) indicates that the H2L4 ligand is bonded with vanadium meridionally in a tridentate dinegative fashion through its deprotonated phenolic-O, deprotonated enolic-O and imine-N atoms. The V-O bond length order is: oxo < phenolato < enolato. H-1 NMR spectra of 4 in CDCl3 solution indicates that it's solid-state structure is retained in solution. Complexes are diamagnetic and exhibit only ligand to metal charge transfer (LMCT) transition band near 530 nm in CH2Cl2 solution in addition to intra-ligand pi-pi* transition band near 335 rim and they display quasi-reversible one electron reduction peak near -0.10 V versus SCE in CH2Cl2 solution. lambda(max) (for LMCT transition) and the reduction peak potential (E-p(c)) values of the complexes are found to be linearly related with the Hammett (sigma) constants of the substituents in the aryloxy ring of the hydrazone ligands. lambda(max) and E-p(c) values show large dependence d lambda(max)/d sigma = 32.54 nm and dE(p)(c)/d sigma = 0.19 V, respectively, on the Hammett constant. (c) 2006 Elsevier B.V. All rights reserved.

High specific surface area LaFeCo perovskites-Synthesis by nanocasting and catalytic behavior in the reduction of NO with CO

LaFe(1-x)CO(x)O(3) perovskites were conventionally or nanocasting synthesized. The nanocasting involved the preparation of a micro-mesoporous carbon mould using a Silica Aerosil 200 and a carbon source. Then, perovskites were carbon cast at 800 degrees C. The solids were characterized by XRD, N(2) sorption, FTIR, TGA/DTG, SEM and TEM. N(2) sorption evidenced that the nanocast perovskites did not show significant intraparticle porosity in despite of their enhanced (30-50 m(2)/g) specific surface area (SSA). Nevertheless, TEM images, XRD and Rietveld refinement data showed that the solids are constituted at least by 97 wt% of perovskite phase and by agglomerates smaller than 100 nm constituted by crystallites of about 6 nm. TGA/DTG results demonstrated carbon oxidation during the perovskite formation, thus eliminating the template effect and facilitating the occurrence of sintering, which limited the SSA increase. The nanocast perovskites were more active in the reduction of NO than the uncast ones, behavior that was attributed to the increase in their SSA that allows the exposure of a higher number of accessible active sites. However, the perovskite composition and the presence of impurities can reduce the effect of the improvement of the textural properties. The nanocast perovskites also showed high thermal and catalytic stability, corroborating their potential as catalysts for the studied reaction. (C) 2009 Elsevier B.V. All rights reserved.

Enamel matrix derivative induces matrix synthesis by cultured human periodontal fibroblast cells

Background: Periodontal wound healing and regeneration require that new matrix be synthesized, creating an environment into which cells can migrate. One agent which has been described as promoting periodontal regeneration is an enamel matrix protein derivative (EMD). Since no specific growth factors have been identified in EMD preparations, it is postulated that EMD acts as a matrix enhancement factor. This study was designed to investigate the effect of EMD in vitro on matrix synthesis by cultured periodontal fibroblasts. Methods: The matrix response of the cells was evaluated by determination of the total proteoglycan synthesis, glycosaminoglycan profile, and hyaluronan synthesis by the uptake of radiolabeled precursors. The response of the individual proteoglycans, versican, decorin, and biglycan were examined at the mRNA level by Northern blot analysis. Hyaluronan synthesis was probed by identifying the isotypes of hyaluronan synthase (HAS) expressed in periodontal fibroblasts as HAS-2 and HAS-3 and the effect of EMD on the levels of mRNA for each enzyme was monitored by reverse transcription polymerase chain reaction (RTPCR). Comparisons were made between gingival fibroblast (GF) cells and periodontal ligament (PDLF) cells. Results: EMD was found to significantly affect the synthesis of the mRNAs for the matrix proteoglycans versican, biglycan, and decorin, producing a response similar to, but potentially greater than, mitogenic cytokines. EMD also stimulated hyaluronan synthesis in both GF and PDLF cells. Although mRNA for HAS-2 was elevated in GF after exposure to EMD, the PDLF did not show a similar response. Therefore, the point at which the stimulation of hyaluronan becomes effective may not be at the level of stimulation of the mRNA for hyaluronan synthase, but, rather, at a later point in the pathway of regulation of hyaluronan synthesis. In all cases, GF cells appeared to be more responsive to EMD than PDLF cells in vitro. Conclusions: EMD has the potential to significantly modulate matrix synthesis in a manner consistent with early regenerative events.

Mechanism of extracellular silver nanoparticles synthesis by Stereum hirsutum and Fusarium oxysporum

The increasing interest for greener and biological methods of synthesis has led to the development of non-toxic and comparatively more bioactive nanoparticles. Unlike physical and chemical methods of nanoparticle synthesis, microbial synthesis in general and mycosynthesis in particular is cost-effective and environment-friendly. However, different aspects, such as the rate of synthesis, monodispersity and downstream processing, need to be improved. Many fungal-based mechanisms have been proposed for the formation of silver nanoparticles (AgNPs), mainly those involving the presence of nitrate reductase, which has been detected in filtered fungus cell used for AgNPs production. There is a general acceptance that nitrate reductase is the main responsible for the reduction of Ag ions for the formation of AgNPs. However, this generally accepted mechanism for fungal AgNPs production is not totally understood. In order to elucidate the molecules participating in the mechanistic formation of metal nanoparticles, the current study is focused on the enzymes and other organic compounds involved in the biosynthesis of AgNPs. The use of each free fungal mycelium of both Stereum hirsutum and Fusarium oxysporum will be assessed. In order to identify defective mutants on the nitrate reductase structural gene niaD, fungal cultures of S.hirsutum and F.oxysporum will be selected by chlorate resistance. In addition, in order to verify if each compound identified as key-molecule influenced on the production of nanoparticles, an in vitro assay using different nitrogen sources will be developed. Lately, fungal extracellular enzymes will be measured and an in vitro assay will be done. Finally, The nanoparticle formation and its characterization will be evaluated by UV-visible spectroscopy, electron microscopy (TEM), X-ray diffraction analysis (XRD), Fourier transforms infrared spectroscopy (FTIR), and LC-MS/MS.

Expressive concatenative synthesis by reusing samples from real performance recordings

Here we describe an approach to the expressive synthesis of jazz saxophone melodies that reuses audio recordings and carefully concatenates note samples. The aim is to generate an expressive audio sequence from the analysis of an arbitrary input score using a previously induced performance model and an annotated saxophone note database extracted from real performances. We push the idea of using the same corpus for both inducing an expressive performance model and synthesizing sound by concatenating samples in the corpus. Therefore, a connection between the performers’ instrument sound and performance characteristics is kept during the synthesis process.