A comparison between neodymium doped alumina samples obtained by Pechini and sol-gel methods using thermo-stimulated luminescence and SEM

Neodymium doped and undoped aluminum oxide samples were obtained using two different techniques: Pechini and sol-gel. Fine grained powders were produced using both procedures, which were analyzed using Scanning Electron Microscopy (SEM) and Thermo-Stimulated Luminescence (TSL). Results showed that neodymium ions incorporation is responsible for the creation of two new TSL peaks (125 and 265 degrees C) and, also, for the enhancement of the intrinsic TSL peak at 190 degrees C. An explanation was proposed for these observations. SEM gave the dimensions of the clusters produced by each method, showing that those obtained by Pechini are smaller than the ones produced by sol-gel; it can also explain the higher emission supplied by the first one. (C) 2010 Elsevier B.V. All rights reserved.

TL and OSL properties of KAlSi(3)O(8):Mn, obtained by sol-gel process

Thermoluminescence (TL) and Optically Stimulated Luminescence (OSL) properties of KAlSi(3)O(8):Mn glasses obtained through the sol gel technique were investigated. Samples were obtained with five different molar concentrations of 0.25, 0.5, 1, 2 and 5 mol% of manganese. Transmission Electronic Microscopy (TEM) indicated the occurrence of nanoparticles composed by glass matrix elements with Mn. Best results for TL response were obtained with 0.5 mol% Mn doped sample, which exhibits a TL peak at 180 degrees C. The TL spectrum of this sample presents a broad emission band from 450 to 700 nm with a peak at 575 nm approximately. The emission band fits very well with the characteristic lines of the Mn(2+) emission features. According to this fact, the band at 410 nm can be ascribed to (6)A(1)(S) -> (4)A(1)(G), (4)E(G) transition, while the 545 nm band can be attributed to the superposition of the transitions (6)A(1)(S) -> (4)T(2)(G) and (6)A(1)(S) -> (4)T(1)(G). The dependence of the TL response with the energy of X-rays (27-41 keV) showed a small decrease of the TL intensity in the high energy region. Excitation with blue LEDs showed OSL in the UV region with a fast decay component. (C) 2011 Elsevier Ltd. All rights reserved.

Erbium-activated silica-zirconia planar waveguides prepared by sol-gel route

Er(3+) doped (100-x)SiO(2)-xZrO(2) planar waveguides were prepared by the sol-gel route, with x ranging from 10 up to 30 mol%. Multilayer films doped with 0.3 mol% Er(3+) ions were deposited on fused quartz substrates by the dip-coating technique. The thickness and refractive index were measured by m-line spectroscopy at different wavelengths. The fabrication protocol was optimized in order to confine one propagating mode at 1.5 mu m. Photoluminescence in the near and visible region indicated a crystalline local environment for the Er(3+) ion. (c) 2007 Elsevier B.V. All rights reserved.

Sol-gel preparation of near-infrared broadband emitting Er(3+)-doped SiO(2)-Ta(2)O(5) nanocomposite films

This article reports a study on the preparation, densification process, and structural and optical properties of SiO(2)-Ta(2)O(5) nanocomposite films obtained by the sol-gel process. The films were doped with Er(3+) and the Si:Ta molar ratio was 90:10. Values of refractive index, thickness and vibrational modes in terms of the number of layers and thermal annealing time are described for the films. The densification process is accompanied by OH group elimination, increase in the refractive index, and changes in film thickness. Full densification of the film is acquired after 90 min of annealing at 900 degrees C. The onset of crystallization and devitrification, with the growth of Ta(2)O(5) nanocrystals occurs with film densification, evidenced by high-resolution transmission electron microscopy. The Er(3+)-doped nanocomposite annealed at 900 degrees C consists of Ta(2)O(5) nanoparticles, with sizes around 2 nm, dispersed in the SiO(2) amorphous phase. The main emission peak of the film is detected at around 1532 nm, which can be assigned to the (4)I(13/2)->(4)I(15/2) transition of the Er(3+) ions present in the nanocomposites. This band has a full width at half medium of 64 nm, and the lifetime measured for the (4)I(13/2) levels is 5.4 ms, which is broader compared to those of other silicate systems. In conclusion, the films obtained in this work are excellent candidates for use as active planar waveguide. (C) 2010 Elsevier B.V. All rights reserved.

Effect of mesoporosity of vanadium oxide prepared by sol-gel process as cathodic material evaluated by cyclability during Li(+) insertion/deinsertion

The effect of pore structure on the behavior of lithium intercalation into an electrode containing porous V(2)O(5) film has been investigated and compared with the electrode containing a non-porous V(2)O(5) film. X-ray diffraction patterns indicate a lamellar structure for both materials. Nitrogen adsorption isotherms, t-plot method, and Scanning Electronic Microscopy show that the route employed for the preparation of mesoporous V(2)O(5) was successful. The electrochemical performance of these matrices as lithium intercalation cathode materials was evaluated. The porous material reaches stability after several cycles more easily compared with the V(2)O(5) xerogel. Lithium intercalation into the porous V(2)O(5) film electrode is crucially influenced by pore surface and film surface irregularity, in contrast with the non-porous surface of the V(2)O(5) xerogel.

Characterization of pore structure and coordination of titanium in TiO2 and SiO2-TiO2 sol-pillared clays

Titania sol-pillared clay (TiO2 PILC) and silica-titania sol-pillared clay (SiO2-TiO2 PILC) were synthesized by the sol-gel method. Supercritical drying (SCD) and treatment with quaternary ammonium surfactants were used to tailor the pore structure of the resulting clay. It was found that SCD approach increased the external surface area of the PILCs dramatically and that treatment with surfactants could be used to tailor pore size because the mesopore formation in the galleries between the clay layers follows the templating mechanism as observed in the synthesis of MCM-41 materials. Highly mesoporous solids were thus obtained. In calcined TiO2 PILC, ultrafine crystallites in anatase phase, which are active for photocatalytic oxidation of organics, were observed. In SiO2-TiO2 PILCs and their derivatives, titanium was highly dispersed in the matrix of silica and no crystal phase was observed. The highly dispersed titanium sites are good catalytic centers for selective oxidation of organic compounds. (C) 2001 Academic Press.

Novel molecular sieve silica (MSS) membranes: characterisation and permeation of single-step and two-step sol-gel membranes

High quality MSS membranes were synthesised by a single-step and two-step catalysed hydrolyses employing tetraethylorthosilicate (TEOS), absolute ethanol (EtOH), I M nitric acid (HNO3) and distilled water (H2O). The Si-29 NMR results showed that the two-step xerogels consistently had more contribution of silanol groups (Q(3) and Q(2)) than the single-step xerogel. According to the fractal theory, high contribution of Q(2) and Q(3) species are responsible for the formation of weakly branched systems leading to low pore volume of microporous dimension. The transport of diffusing gases in these membranes is shown to be activated as the permeance increased with temperature. Albeit the permeance of He for both single-step and two-step membranes are very similar, the two-step membranes permselectivity (ideal separation factor) for He/CO2 (69-319) and He/CH4 (585-958) are one to two orders of magnitude higher than the single-step membranes results of 2-7 and 69, respectively. The two-step membranes have high activation energy for He and H-2 permeance, in excess of 16 kJ mol(-1). The mobility energy for He permeance is three to six-fold higher for the two-step than the single-step membranes. As the mobility energy is higher for small pores than large pores and coupled with the permselectivity results, the two-step catalysed hydrolysis sol-gel process resulted in the formation of pore sizes in the region of 3 Angstrom while the single-step process tended to produce slightly larger pores. (C) 2002 Elsevier Science B.V. All rights reserved.

Análise de crescimento do amarílis cultivado a pleno sol

O cultivo de amarílis (Hippeastrum x hybridum Hort.) visa, principalmente, à produção e comercialização de bulbos para exportação. Informações sobre o seu ciclo de crescimento ainda são incongruentes. Assim, foi objetivo realizar medições que possam contribuir com estudos de análise de crescimento do amarílis var. Orange Souvereign, cultivado a pleno sol, nas condições encontradas em Santo Antônio de Posse, Estado de São Paulo. O delineamento experimental empregado foi o inteiramente casualizado. Utilizaram-se plantas cultivadas em uma área de 2 ha, onde os dados foram coletados mensalmente, durante 14 meses, de forma aleatória. Para cada uma das características analisadas foram utilizadas quatro repetições de 10 plantas. A área foliar determinada ao final do experimento foi de, em média, 3.102,65 cm², tendo em vista 10 folhas por planta. O diâmetro do bulbo aumentou, gradualmente, durante todo o período de produção, finalizando aos 420 dias após plantio, com 9,15 cm em média. A massa fresca total ao final do ciclo foi de, em média, 1.050,55 g, dos quais 39% (410 g) foram de massa fresca obtida pelo bulbo da forma como é comercializado (bulbo + raízes). Os índices fisiológicos da análise de crescimento (taxa de crescimento absoluto, taxa de crescimento relativo, taxa de assimilação líquida e razão de área foliar) demonstraram o comportamento da planta no campo, tendo o sistema assimilatório atingido bom desempenho nas condições de cultivo. O crescimento de amarílis foi considerado satisfatório do ponto de vista comercial.

Resultados do inquérito alimentar realizado nas cidades de Apiaí, Ribeira e Barra do Chapéu (São Paulo, Brasil)

Foram apresentados os resultados do inquérito alimentar realizado na região do Vale do Ribeira, nas cidades de Apiaí, Ribeira e Barra do Chapéu (São Paulo, Brasil), em amostra constituída por 154 famílias, totalizando 939 indivíduos. O método utilizado para o levantamento foi o de pesagem "um dia sete dias". A análise dos dados evidenciou que em Apiaí as adequações médias de proteína, ferro e niacina foram as únicas que ultrapassaram os 100% dos valores recomendados, enquanto que, na cidade de Barra do Chapéu este fato ocorreu em relação à ferro, niacina e vitamina B1. Com referência à cidade de Ribeira, apenas niacina atingiu uma adequação de 100%, sendo que os demais nutrientes apresentaram resultados inferiores.

Síntese sol-gel de biomateriais à base de água de fontes hidrotermais para otimização do comportamento celular e regeneração dos tecidos ósseos

Dissertação de Mestrado, Ciências Biomédicas, 18 de Março de 2016, Universidade dos Açores.

Prevalência de lesões labiais em trabalhadores de praia e fatores associados

OBJETIVO: Analisar a prevalência de lesões labiais decorrentes da exposição solar e potenciais associações em trabalhadores de praia. MÉTODOS: Estudo transversal com 362 trabalhadores de cinco praias urbanas em Natal, RN, de agosto a dezembro de 2010. Os participantes responderam um questionário validado com dados pessoais, de ocupação e de saúde e passaram por exame clínico dos lábios feito por pesquisadores calibrados. As possíveis associações das variáveis sociodemográficas, ocupacionais e de saúde geral com a presença de lesões labiais foram avaliadas pelo teste do qui-quadrado para um nível de significância de 5%. A análise multivariada foi feita utilizando-se a regressão robusta de Poisson. RESULTADOS: Dos trabalhadores examinados, 27,1% apresentavam lesões labiais. Desses, 76,8% eram do sexo masculino; 61,6% tinham pele morena ou negra; 94,5% trabalhavam informalmente; e 85,4% trabalhavam expostos ao sol. A maioria (81,1%) relatou uso de algum tipo de fotoproteção: protetor solar (38,7%); protetor labial (15,3%); boné/chapéu (72,4%). Aproximadamente 28% eram fumantes e 48% consumiam álcool regularmente. A fotoproteção com uso de boné/chapéu foi associada à presença de lesões labiais decorrentes da exposição solar. CONCLUSÕES: Observou-se alta prevalência de lesões labiais nos indivíduos expostos ao sol, a qual foi associada ao uso de boné/chapéu como forma de fotoproteção.

Télédetection en milieu périurbain. Détection et localisation du changement de l'occupation du sol par intégration des donnés-satellite SPOT HRV dans un système d'information géographique

Thèse pour obtenir le grade de DOCTEUR DE L' UNIVERSITÉ PARIS XII, Discipline: Urbanisme Aménagement

Caracterização de Cutinase imobilizada em matriz de sol-gel

Dissertação apresentada à Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa para cumprimento dos requisitos necessários à obtenção do grau de Mestre em Biotecnologia

Sol-gel-based biosensing applied to medicinal science

Biosensors have opened new horizons in biomedical analysis, by ensuring increased assay speed and flexibility, and allowing point-of-care applications, multi-target analyses, automation and reduced costs of testing. This has been a result of many studies merging nanotechnology with biochemistry over the years, thereby enabling the creation of more suitable environments to biological receptors and their substitution by synthetic analogue materials. Sol-gel chemistry, among other materials, is deeply involved in this process. Sol-gel processing allows the immobilization of organic molecules, biomacromolecules and cells maintaining their properties and activities, permitting their integration into different transduction devices, of electrochemical or optical nature, for single or multiple analyses. Sol-gel also allows to the production of synthetic materials mimicking the activity of natural receptors, while bringing advantages, mostly in terms of cost and stability. Moreover, the biocompatibility of sol-gel materials structures of biological nature allowed the use of these materials in emerging in vivo applications. In this chapter, biosensors for biomedical applications based on sol-gel derived composites are presented, compared and described, along with current emerging applications in vivo, concerning drug delivery or biomaterials. Sol-gel materials are shown as a promising tool for current, emerging and future medical applications. - See more at: http://www.eurekaselect.com/127191/article#sthash.iPqqyhox.dpuf