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The effect of silver nanoparticles: a chronic in vivo study for the evaluation of hepatic mitochondrial toxicity

Silva, Rui Gonçalo Teixeira da
Fonte: Universidade de Coimbra Publicador: Universidade de Coimbra
Tipo: Dissertação de Mestrado
ENG
Relevância na Pesquisa
16.24%
Manufactured nanomaterials have been of extreme importance due to the beneficial physicochemical properties they possess compared to bulk parental materials. However, the properties that make them so attractive are also the same that can cause harm both to humans and environment. Over the last years there has been a rapid development of the nanotechnology industry and the inevitable human exposure tends rapidly to expand, accompanied by potential for adverse health effects. Among all used nanoparticles (NPs), silver nanoparticles (AgNPs) have the highest level of commercialization. Silver has been used for decades in medical healthcare due to its known antibacterial properties. One can also observe AgNPs in products used daily such as cosmetics, lotions, toothpastes, soaps, sunscreen, clothing and electronics. Over the last years, nanoparticles have been the subject of intense research for use in biomedicine, namely as biosensors, drug-delivery agents and imaging contrast agents, which take advantage of their unique optical properties. Human exposure to AgNPs can occur through different ways: inhalation, ingestion, injection and dermal contact. As a major organ of detoxification, the liver is one of the most important targets after AgNPs exposure. The main toxicological concern is the fact that AgNPs preferentially accumulate in mitochondria. Since mitochondria have an essential bioenergetic function...

Characterization of new lanthanide complexes and nanoparticles as bimodal imaging agents

Paula, Carlos Tadeu Barreirinhas
Fonte: Universidade de Coimbra Publicador: Universidade de Coimbra
Tipo: Dissertação de Mestrado
ENG
Relevância na Pesquisa
16.24%
A Imagem por Ressonância Magnética (IRM) é uma modalidade de imagem médica baseada em ressonância magnética nuclear (RMN), onde um mapa de sinais de 1H NMR de uma determinada amostra é gerado. É uma excelente técnica de imagem, que permite a aquisição não-invasiva de imagens anatómicas de elevada resolução espacial. No entanto, a IRM tem como principal problema a sua baixa sensibilidade. Este inconveniente pode ser ultrapassado com a introdução de agentes externos que aumentem a intensidade de sinal. Estes agentes podem ser denominados agentes de contraste (AC) e pode ter várias formas. Uma dos tipos de moléculas mais vulgarmente utilizadas para induzir uma melhoria na intensidade do sinal são os complexos lantanídeos, sobretudo os complexos de Gd3 +. Outra possível estratégia para melhorar a qualidade das imagens obtidas, consiste na combinação de diferentes métodos de imagem, a fim de criar um agente multimodal. Um dos campos de investigação mais usual é a bimodalidade Imagem óptica (IO)/IRM. A IO, devido às suas características, pode apresentar um ganho significativo em termos de sensibilidade. Os recentes avanços na nanotecnologia, mostrou que os Quantum Dots (QDs) são uma das aplicações mais promissoras da ciência dos materiais na Biologia. Eles podem ser utilizados na construção de AC para IO muito eficientes. Neste trabalho é apresentada a construção de dois tipos de sistemas de imagem molecular. Em primeiro lugar...

O domínio aeroespacial nas manifestações de poder : efeitos nas relações internacionais

Tomé, António Joaquim Viana de Almeida
Fonte: Repositório Científico Lusófona Publicador: Repositório Científico Lusófona
Tipo: Tese de Doutorado
POR
Relevância na Pesquisa
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O poder aeroespacial constitui factor crucial no estudo das transformações operadas nas relações internacionais, obrigando ao aprofundar e à redefinição conceptual da importância do poder aéreo e espacial na condução da política do Estado através da respectiva capacidade de prevenção do fenómeno guerra. Da planetização das comunicações em tempo real surgiu um sistema internacional único, materializado na ampliação dos instrumentos de coerção estratégica mundial de um poder aéreo de projecção global e na redução dimensional do conjunto espaço-tempo. O dinamismo das forças transnacionais torna premente o estudo científico e a adopção de novos conceitos que possam actualizar as limitadas teorias clássicas centradas no Estado. A geoeconomia obrigou ao actualizar das reinterpretações geoestratégicas e geopolíticas, face às guerras de novo tipo e ao perfilar de novos poderes, com a formulação de novos paradigmas, como a racionalpolitik, por os clássicos já não totalizarem o enquadramento conceptual da conjuntura. Implicando a reformulação de áreas fundamentais da Estratégia clássica, em consequência da consolidação das novas estratégias aéreas e espaciais ampliadas pelas nanotecnologias aeronáuticas...

Nanopartículas de PCL com acetato de hidrocortisona como uma terapia dermatológica inovadora para a dermatite atópica; Hydrocortisone acetate-loaded PCL nanoparticles as an innovative dermatological therapy for atopic dermatitis

Reis, Catarina Pinto; Jerónimo, Ana Rita Gonçalves; Pinto, Pedro Contreiras; Silva, Catarina Oliveira; Candeias, Sara
Fonte: Repositório Científico Lusófona Publicador: Repositório Científico Lusófona
Tipo: Artigo de Revista Científica
POR
Relevância na Pesquisa
16.24%
A dermatite atópica é uma patologia cutânea crónica que requer cuidados intensivos da pele e tratamento farmacológico; contudo, os tratamentos disponíveis necessitam urgentemente de ser melhorados, especialmente quando utilizados por períodos longos ou em grupos específicos (ex: crianças). A nanotecnologia tem contribuído com sistemas de veiculação inovadores e pode oferecer terapias efectivas e direcionadas. Os objectivos deste estudo centraram-se na preparação caracterização das nanopartículas de policaprolactona carregadas com acetato de hidrocortisona em termos das propriedades físico-químicas, eficiência de encapsulação, ensaios de libertação in vitro e ensaios de segurança dos excipientes utilizados em voluntários humanos. As nanopartículas produzidas apresentaram um tamanho médio de 258,4 24,5 nm e um índice de polidispersão de 0,084. O potencial zeta foi -4,39 0,62 mV e a eficiência de encapsulação foi 36,32 0,03 %. A libertação in vitro do fármaco foi controlada ao longo do tempo. Além disso, os testes de segurança indicaram que os excipientes foram bem tolerados. Este estudo demonstra que as nanopartículas de policaprolactona são sistemas estáveis para veiculação de acetato de hidrocortisona que poderão conduzir a uma libertação prolongada do fármaco...

Novas estratégias para o tratamento da alopécia

Rebelo, Ana Santos
Fonte: Repositório Científico Lusófona Publicador: Repositório Científico Lusófona
Tipo: Dissertação de Mestrado
POR
Relevância na Pesquisa
16.24%
A alopécia é uma doença dermatológica inflamatória crónica comum que afeta os folículos pilosos e define-se pela perda parcial ou total dos pêlos ou cabelos. A sua etiologia e subsequente desenvolvimento não estão ainda totalmente esclarecidos. A alopécia androgenética, é a forma mais comum de perda de cabelo em ambos os sexos, sendo, por isso, o principal foco desta dissertação. É classificada como sendo uma alopécia não cicatricial e caracteriza-se por uma perda progressiva do diâmetro, comprimento, e pigmentação do cabelo. Os dois principais fatores causais deste distúrbio são os níveis de androgénios e fatores genéticos. Como consequência têm surgido inúmeros estudos que procuram estratégias e tratamentos mais eficazes e seguros para a terapêutica desta patologia. Sem tratamento, a alopécia androgenética é uma condição progressiva. Com o tratamento existente, habitualmente prescrito e com estudos mais alargados relativos à sua ação, eficácia e segurança, têm sido observadas melhorias significativas mas não curativas. O minoxidil tópico e finasteride oral, são os fármacos, até aos dias de hoje, mais utilizados no tratamento da alopécia androgenética, com taxas de sucesso significativas e clinicamente reconhecidas...

Singlet oxygen quantum yields (Φd) in water using beetroot extract and an array of LEDs

BONACIN, Juliano A.; ENGELMANN, Fábio M.; SEVERINO, Divinomar; TOMA, Henrique E.; BAPTISTA, Mauricio S.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
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It is proposed a simple and inexpensive strategy to determine singlet oxygen (¹O2) quantum yields (ΦΔ) of photosensitizers (PS) in water using beetroot extract containing betacyanin (Bc) and a set of light emitting diodes (LEDs) for excitation. Bc, a cationic natural dye, was obtained by flash chromatography purification from the red beet extract (Beta vulgaris) and employed as a convenient probe for ¹O2 detection. Solutions of Bc and PS were illuminated with an array of LEDs adapted in the cuvette compartment of a commercial spectrophotometer, and the decrease in Bc absorbance was followed as a function of time. Bc photobleaching decreased in de-aerated solution and increased in D2O, indicating the involvement of ¹O2. The observed photobleaching rate constant (k obs) was proportional to the LED intensity, concentration and ΦΔ of the PS. By keeping the light source constant we could estimate the overlap integral (R) between the LED emission and PS absorbance for different PS concentrations. The slope of R versus k obs is the value of the photobleaching rate constant (k), which was shown to be proportional to ΦΔ. Values of ΦΔ obtained by this method were compared with those obtained by measuring NIR (near infrared) emission for a series phenothiazine dyes.; É proposta uma estratégia simples e barata para determinar rendimentos quânticos (ΦΔ) de oxigênio singlete (¹O2) de fotossensibilizadores (PS) em água utilizando extrato de beterraba contendo betacianina (Bc) e um conjunto de diodos emissores de luz (LEDs) para excitação. Bc...

Polymer matrix sensitizing effect on photoluminescence properties of Eu(3+)-beta-diketonate complex doped into poly-beta-hydroxybutyrate (PHB) in film form

KAI, Jiang; PARRA, Duclerc Fernandes; BRITO, Hermi Felinto
Fonte: ROYAL SOC CHEMISTRY Publicador: ROYAL SOC CHEMISTRY
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
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In this work is reported the sensitization effect by polymer matrices on the photoluminescence properties of diaquatris(thenoyltrifluoroacetonate)europium(III), [Eu(tta)(3)(H(2)O)(2)], doped into poly-beta-hydroxybutyrate (PHB) with doping percentage at 1, 3, 5, 7 and 10% (mass) in film form. TGA results indicated that the Eu(3+) complex precursor was immobilized in the polymer matrix by the interaction between the Eu(3+) complex and the oxygen atoms of the PHB polymer when the rare earth complex was incorporated in the polymeric host. The thermal behaviour of these luminescent systems is similar to that of the undoped polymer, however, the T(onset) temperature of decomposition decreases with increase of the complex doping concentration. The emission spectra of the Eu(3+) complex doped PHB films recorded at 298 K exhibited the five characteristic bands arising from the (5)D(0) -> (7)F(J) intraconfigurational transitions (J = 0-4). The fact that the quantum efficiencies eta of the doped film increased significantly revealed that the polymer matrix acts as an efficient co-sensitizer for Eu(3+) luminescent centres and therefore enhances the quantum efficiency of the emitter (5)D(0) level. The luminescence intensity decreases, however...

Structure and luminescent investigation of the Ln(III)-beta-diketonate complexes containing tertiary amides

Teotonio, Ercules E. S.; Brito, Hermi Felinto de; Sa, Gilberto F. de; Felinto, Maria Claudia F. C.; Santos, Regina Helena de Almeida; Fuquen, Rodolfo Moreno; Costa, Israel F.; Kennedy, Alan R.; Gilmore, Denise; Faustino, Wagner M.
Fonte: PERGAMON-ELSEVIER SCIENCE LTD; OXFORD Publicador: PERGAMON-ELSEVIER SCIENCE LTD; OXFORD
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
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The synthesis and photoluminescent properties of Ln(III)-thenoyltrifluoroacetonate and dibenzoylmethanate complexes (Ln = Eu(III) and Gd(III) ions) containing tertiary amides such as dimethylacetamide (DMA), dimethylformamide (DMF), and dimethylbenzamide (DMB) as neutral ligands are reported. The Ln complexes were characterized by elemental analysis, complexometric titration with EDTA, and infrared spectroscopy. Single-crystal X-ray structure data of the [Eu(DBM)(3).(DMA)] compound indicates that this complex crystallizes in the triclinic system, space group PT with the following cell parameters: a = 10.2580(3) angstrom, b = 10.3843(2) angstrom, c= 22.3517(5) angstrom, alpha = 78.906(2)degrees, beta = 78.049(2)degrees, lambda= 63.239(2)degrees, V= 2066.41(9) angstrom(3), and Z = 2. The coordination polyhedron for the Eu(III) complex may be described as an approximate C-2v distorted monocapped trigonal prism. The optical properties of the Eu(III) complexes were studied based on the intensity parameters and luminescence quantum yield (q). The values of the ohm(2) parameter of the Eu-DBM complexes are larger than those for the Eu-TTA complexes, indicating that the Eu(III) ion is in a more polarizable chemical environment in the former case. The geometries of the complexes have been optimized by using the Sparkle Model...

Bilipid membrane phase characterization by reflectance anisotropy spectroscopy (RAS)

Favero, P. P.; Ferraz, Armando Corbani; Baptista, Mauricio da Silva; Miotto, R.
Fonte: SPIE; San Francisco Publicador: SPIE; San Francisco
Tipo: Artigo de Revista Científica
ENG
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In this work we propose the use of experimental and theoretical reflectance anisotropy spectra (RAS) as a new tool to identify structural and dynamical aspects of the bilipid membrane and its various constituent molecules. The role of geometric details at the atomic level and macroscopic quantities, such as the membrane curvature and tilt for the different gel phases, in the theoretical RAS spectra (using Kohn-Sham density functional theory (KS-DFT)) are presented. Then the results are compared to the experimentally measured spectra taken from other techniques.; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Gold ion implantation into alumina using an “inverted ion source” configuration.

Salvadori, Maria Cecilia Barbosa da Silveira; Teixeira, Fernanda de Sá; Sgubin, Leonardo Gimenes; Araujo, Wagner Wlysses Rodrigues de; Spirin, R. E.; Cattani, Mauro Sergio Dorsa; Oks, E. M.; Brown, Ian Gordon
Fonte: AIP Publishing; AIP Publishing LLC; Nova York Publicador: AIP Publishing; AIP Publishing LLC; Nova York
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
16.24%
We describe an approach to ion implantation in which the plasma and its electronics are held at ground potential and the ion beam is injected into a space held at high negative potential, allowing considerable savings both economically and technologically. We used an “inverted ion implanter” of this kind to carry out implantation of gold into alumina, with Au ion energy 40 keV and dose (3–9) × 1016 cm−2. Resistivity was measured in situ as a function of dose and compared with predictions of a model based on percolation theory, in which electron transport in the composite is explained by conduction through a random resistor network formed by Au nanoparticles. Excellent agreement is found between the experimental results and the theory.; FAPESP; CNPq

Electronic Structure Calculations in a 2D SixGe1-x Alloy Under an Applied Electric Field.

Sousa, José Eduardo Padilha de; Pontes, Renato Borges; Rocha, Leandro Seixas; Silva, Antonio Jose Roque da; Fazzio, Adalberto
Fonte: Baltimore Publicador: Baltimore
Tipo: Conferência ou Objeto de Conferência
POR
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16.24%
The recent advances and promises in nanoscience and nanotechnology have been focused on hexagonal materials, mainly on carbon-based nanostructures. Recently, new candidates have been raised, where the greatest efforts are devoted to a new hexagonal and buckled material made of silicon, named Silicene. This new material presents an energy gap due to spin-orbit interaction of approximately 1.5 meV, where the measurement of quantum spin Hall effect(QSHE) can be made experimentally. Some investigations also show that the QSHE in 2D low-buckled hexagonal structures of germanium is present. Since the similarities, and at the same time the differences, between Si and Ge, over the years, have motivated a lot of investigations in these materials. In this work we performed systematic investigations on the electronic structure and band topology in both ordered and disordered SixGe1-x alloys monolayer with 2D honeycomb geometry by first-principles calculations. We show that an applied electric field can tune the gap size for both alloys. However, as a function of electric field, the disordered alloy presents a W-shaped behavior, similarly to the pure Si or Ge, whereas for the ordered alloy a V-shaped behavior is observed.; CAPES; CNPq; FAPESP

Structural and reduction studies of ZrO2-CeO2:Ni for application in SOFC anodes.

Bacani, Rebeca; Costa, Antonia Daniele Souza Bruno; Fantini, Marcia Carvalho de Abreu; Martins, T. S.; Larrondo, S. A.; Lamas, D. G.
Fonte: Vellidis Congress Center; Tessaloniki Publicador: Vellidis Congress Center; Tessaloniki
Tipo: Conferência ou Objeto de Conferência
ENG
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16.24%
Zirconia-ceria solid-solutions are extensively used as promoters for three-way catalysts, which are applied in the control of NOx, CO and hydrocarbons emission from automotive exhausts. In addition, thesematerials can be used as anodes in solid oxide fuel cells (SOFCs) operated with hydrocarbons. There areonly few works on ZrO2-CeO2 ordered mesoporous materials for catalytic applications and for anodes inSOFCs. The interest in these anodes relies on the fact that ZrO2-CeO2materials are mixed ionic/electronic conductors in reducing atmosphere and, therefore, fuel oxidation is produced on its entire surface, while it only occurs in the [anode/electrolyte/gas] interface (triple-phase boundaries) for electronic conductors. In this work, a synthesis method was developed usingZr and Ce chloride precursors, HCl aqueous solution, Pluronic P123 as the structure directing agent, NH4OH to adjust the pH (3-4) and a Teflon autoclave to perform hydrothermal treatment (80ºC/48 hours). The samples were dried and calcined, until 540ºC in N2and 4 hours in air. The X-ray diffraction data showed that powders with higher CeO2 content are formed by a larger fraction of the cubic CeO2 phase, while for a lower CeO2content the major crystalline structure is the tetragonal ZrO2 phase. The NiO impregnation was made with an ethanol dispersion of Ni(NO3)×6H2O. The resulting powder was calcinated in air until 350ºC for 2 hours. Temperature-programmed reduction (TPR) data were collected in order to evaluate the reduction profiles of ZrO2-x%CeO2:Ni samples in H2/Ar atmosphere. Results showed lower reduction temperatures for all ceria content in samples comparing to a NiO standard.

Size-dependent phase transitions in nanostructured zirconia-scandia solid solutions.

Abdala, P. M.; Craievich, Aldo Felix; Lamas, D. G.
Fonte: Laboratório Nacional de Luz Síncrotron.; Campinas Publicador: Laboratório Nacional de Luz Síncrotron.; Campinas
Tipo: Conferência ou Objeto de Conferência
ENG
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16.24%
Size effects on phase stability and phase transitions in technologically relevant materials have received growing attention. Several works reported that metastable phases can be retained at room temperature in nanomaterials, these phases generally corresponding to the high-temperature polymorph of the same material in bulk state. Additionally, size-dependent shifts in solubility limits and/or in the transition temperatures for on heating or on cooling cycles have been observed. ZrO2-Sc2O3 (zirconia-scandia) solid solutions are known to exhibit very high oxygen ion conductivity provided their structure is composed of cubic and/or pseudocubic tetragonal phases. Unfortunately, for solid zirconia-scandia polycrystalline samples with typical micrometrical average crystal sizes, the high-conductivity cubic phase is only stable above 600°C. Depending on composition, three low-conductivity rhombo-hedral phases (β, γ and δ) are stable below 600°C down to room temperature, within the compositional range of interest for SOFCs. In previous investigations, we showed that the rhombohedral phases can be avoided in nanopowders with average crystallite size lower than 35 nm.; LNLS; CNPq; ANPCyT; CLAF

Photoluminescence of core-shell nanoparticles made from yttrium stabilized zirconia powder grain coated with alumina

Gonçalves, Rosana F.; Figueiredo, José T. O.; Figueiredo, Alberthmeiry T.; Siu Li, Máximo; Longo, Elson; Godinho, Mario J.
Fonte: Royal Society of Chemistry - RSC; Cambridge Publicador: Royal Society of Chemistry - RSC; Cambridge
Tipo: Artigo de Revista Científica
ENG
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A YSZ@Al2O3 nanocomposite was obtained by Al2O3 coating on the surface of yttrium stabilized zirconia via a polymeric precursor method. The resulting core–shell structures were characterized by X-ray diffraction, scanning electron microscopy, transmission electronic microscopy and PL spectra. The TEM micrographs clearly show a homogeneous Al2O3 shell around the ZrO2 core. The observed PL is related to surface–interface defects. Such novel technologies can, in principle, explore materials which are not available in the bulk single crystal form but their figure-of-merit is dramatically dependent on the surface–interface defect states.; FAPEG; CNPq; CNPq / Instituto Nacional de Ciência e Tecnologia dos Materiais em Nanotecnologia (INCTMN); CAPES

Dynamics of photoexcited carriers in the presence of disorder in radial heterostructured GaAs/AlGaAs/GaAs nanowires

Guimarães, Francisco Eduardo Gontijo; Caface, R. A.; Arakaki, Haroldo; Souza, Carlos Alberto de; Pusep, Yuri A.
Fonte: American Institute of Physics - AIP; College Park Publicador: American Institute of Physics - AIP; College Park
Tipo: Artigo de Revista Científica
ENG
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Time-resolved photoluminescence was employed to study electron-hole dynamics in radial heterostructured GaAs/AlGaAs/GaAs core/inner shell/outer shell nanowires. It was found that impurity random potential results in a red shift of the recombination time maximum with respect to the photoluminescence peak energy.; FAPESP; CNPq

Replication of submicrometric organized structures of block copolymer from coordination-polymer templates

Longaresi, R. H.; Travençolo, B. A. N.; Silva, L. C.; Silva, Marcelo de Assumpcao Pereira da; Carvalho, A. J. F.; Costa, Luciano da Fontoura; Faria, Roberto Mendonça
Fonte: American Scientific Publishers - ASP; Valencia Publicador: American Scientific Publishers - ASP; Valencia
Tipo: Artigo de Revista Científica
ENG
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16.24%
This paper presents fabrication of a submicrometric template obtained from self-organized well-ordered pattern of nanostructured (poly(styrene)-b-poly(ethene-co-butene)-b-poly(styrene) (SEBS) copolymer. The SEBS ordered structure was formed on mica substrate, in which a thin liquid film of SEBS/Toluene solution was deposited by dip-coating procedure, and after the solvent evaporation, SEBS droplets are spontaneously displayed in a hexagonal arrangement. The molding template was made of PDMS by a soft lithography process and replicas of epoxy forming the original hexagonal pattern with reasonable accuracy. All structures were studied by AFM images, using quantitative computational analyses: hexagonality index and radial distribution functions. The computational analyses showed that the high spacial order in the SEBS nanostructures was followed by the produced mold although and the replica. Also we observed that the original pattern presented 1.7% of dislocation defects (from the hexagonality), while the replica reached 5% showing the success of soft lithography process of nano templates.

Experimental and theoretical approach of nanocrystalline TiO2 with antifungal activity

Longo, Valéria M.; Picon, Francini C.; Zamperini, Camila; Albuquerque, Anderson R.; Sambrano, Julio R.; Vergani, Carlos E.; Machado, Ana L.; Andrés, Juan; Hernandes, Antônio Carlos; Varela, José A.; Longo, Elson
Fonte: Elsevier BV; Amsterdam Publicador: Elsevier BV; Amsterdam
Tipo: Artigo de Revista Científica
ENG
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Using a solvothermal method for this research we synthesized nanocrystalline titanium dioxide (nc-TiO2) anatase particles with a mean diameter of 5.4 nm and evaluated their potential antifungal effect against planktonic cells of Candida albicans without UV radiation. To complement experimental data, we analyzed structural and electronic properties of both the bulk and the (101) surface of anatase by first-principles calculations. Based on experimental and theoretical results, a reactive O2H* and OH* species formation mechanism was proposed to explain the key factor which facilitates the antifungal activity.; CAPES; CNPq; FAPESP; Generalitat Valenciana (Prometeo 2009/053)

Electrophoretic deposition of BaTi0.85Zr0.15O3 nanopowders

Antonelli, Eduardo; Silva, Ronaldo Santos da; Bernardi, Maria Inês Basso; Hernandes, Antônio Carlos
Fonte: Universidade Federal de São Carlos - Departamento de Engenharia de Materiais; São Carlos Publicador: Universidade Federal de São Carlos - Departamento de Engenharia de Materiais; São Carlos
Tipo: Artigo de Revista Científica
ENG
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The present study reports the results of thick films (20-130 μm) produced through electrophoretic deposition of BaTi0.85Zr0.15O3 (BTZ) nanometric powders synthesized by the Pechini’s method. The BTZ powderscalcined at 600°C/2h presented a single crystalline phase with an average particle size of ~20nm. To thick films deposition, a stable suspension of acetylacetone (Acac) and ethanol (EtOH)was prepared and the powder was deposited on platinum substrates. The viscosity of BTZ powders suspensions as a function of operational pH (OpH)was measured and the reactions between nanoparticles and the media were discussed. A milling process was used to deagglomerate the powders and it had a great influence in the suspension stability and deposition of thick films. Dense and crack-free thick films were obtained after sintering at 1220 °C/1h. The dielectric properties results, comparable with those of bulk BTZ ceramics, suggested potential applications of the EPD process for the deposition of ferroelectric/piezoelectric thick films.; FAPESP; FAPITEC/SE; CNPq; CAPES

Ozone gas sensor based on nanocrystalline SrTi1-xFexO3 thin films

Mastelaro, Valmor Roberto; Zilio, Sérgio Carlos; Silva, Luis F.; Pelissari, Pedro I.; Bernardi, Maria Ines Basso; Guerin, Jacques; Aguir, Khalifa
Fonte: Elsevier; Lausanne Publicador: Elsevier; Lausanne
Tipo: Artigo de Revista Científica
ENG
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We report on the use of nanocrystalline SrTi1−xFexO3 (STF) for sensing ozone gas. Amorphous thin films were evaporated by the electron-beam physical vapor deposition technique and then converted to a polycrystalline form, as shown by X-ray diffraction patterns, after ex situ annealing at a relatively low temperature (550 ◦C). The influence of the iron content on the microstructure was investigated by both scanning electron microscopy (SEM) and atomic force microscopy (AFM), which revealed that the surface roughness of the films increased slightly as the amount of iron increased. Electrical resistance measurements were carried out to determine the response of the films upon exposure to ozone and when compared to other oxide metal sensors, STF films can also be considered as good candidates for application as ozone gas sensors.; CAPES; COFECUB; CNPq; FAPESP

Differential pulse adsorptive stripping voltammetric determination of methotrexate using a functionalized carbon nanotubes-modified glassy carbon electrode

Oliveira, Geiser G.; Janegitz, Bruno C.; Zucolotto, Valtencir; Fatibello Filho, Orlando
Fonte: Versita; Warsaw Publicador: Versita; Warsaw
Tipo: Artigo de Revista Científica
ENG
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A glassy carbon electrode (GC) containing multiwalled functionalized carbon nanotubes (MWCNTs) immobilized within a dihexadecylhydrogenphosphate film (DHP) is proposed as a nanostructured platform for determination of methotrexate (MTX) concentration (a drug used in cancer treatment) using differential pulse adsorptive stripping voltammetry (DPAdSV). The voltammograms for a MTX solution using MWCNTs-DHP/GC electrode presented an oxidation peak potential at 0.98 V vs. Ag/AgCl (3.0 mol L-1 KCl) in a 0.1 mol L-1 sulphuric acid. The apparent heterogeneous electron transfer rate constant of 0.46 s-1 was calculated. The recovery area of 2.62×10-9 mol cm2 was also obtained. Under the optimal experimental conditions, the analytical curve was linear in the MTX concentration range from 5.0×10-8 to 5.0×10-6 mol L-1, with a detection limit of 3.3×10-8 mol L-1. The MWCNTs-DHP/GC electrode can be easily prepared and was applied for the determination of MTX in pharmaceutical formulations, with results similar to those obtained using a high-performance liquid chromatography comparative method.; FAPESP (08/09893-0, 12/02877-4); CNPq; Instituto Nacional de Ciência e Tecnologia de Bioanalítica (INCTBio); CAPES