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Electrochemical, morphological and microstructural characterization of carbon film resistor electrodes for application in electrochemical sensors

Gouveia-Caridade, Carla; Soares, David M.; Liess, Hans-Dieter; Brett, Christopher M.A.
Fonte: Universidade de Coimbra Publicador: Universidade de Coimbra
Tipo: Artigo de Revista Científica Formato: aplication/PDF
ENG
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The electrochemical and microstructural properties of carbon film electrodes made from carbon film electrical resistors of 1.5, 15, 140 [Omega] and 2.0 k[Omega] nominal resistance have been investigated before and after electrochemical pre-treatment at +0.9 V vs SCE, in order to assess the potential use of these carbon film electrodes as electrochemical sensors and as substrates for sensors and biosensors. The results obtained are compared with those at electrodes made from previously investigated 2 [Omega] carbon film resistors. Cyclic voltammetry was performed in acetate buffer and phosphate buffer saline electrolytes and the kinetic parameters of the model redox system Fe(CN)63-/4- obtained. The 1.5 [Omega] resistor electrodes show the best properties for sensor development with wide potential windows, similar electrochemical behaviour to those of 2 [Omega] and close-to-reversible kinetic parameters after electrochemical pre-treatment. The 15 and 140 [Omega] resistor electrodes show wide potential windows although with slower kinetics, whereas the 2.0 k[Omega] resistor electrodes show poor cyclic voltammetric profiles even after pre-treatment. Electrochemical impedance spectroscopy related these findings to the interfacial properties of the electrodes. Microstructural and morphological studies were carried out using contact mode Atomic Force Microscopy (AFM)...

Carbon film electrodes for oxidase-based enzyme sensors in food analysis

Luca, S. De; Florescu, M.; Ghica, M. E.; Lupu, A.; Palleschi, G.; Brett, C. M. A.; Compagnone, D.
Fonte: Universidade de Coimbra Publicador: Universidade de Coimbra
Tipo: Artigo de Revista Científica Formato: aplication/PDF
ENG
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Carbon film resistor electrodes have been evaluated as transducers for the development of multiple oxidase-based enzyme electrode biosensors. The resistor electrodes were first modified with Prussian Blue (PB) and then covered by a layer of covalently immobilized enzyme. Electrochemical impedance spectroscopy was used to characterize the interfacial behaviour of the Prussian Blue modified and enzyme electrodes; the spectra demonstrated that the access of the substrates is essentially unaltered by application of the enzyme layer. These enzyme electrodes were used to detect the substrate of the oxidase (glucose, ethanol, lactate, glutamate) via reduction of hydrogen peroxide at +50 mV versus Ag/AgCl in the low micromolar range. Response times were 1-2 min. Finally, the glucose, ethanol and lactate electrochemical biosensors were used to analyse complex food matrices--must, wine and yoghurt. Data obtained by the single standard addition method were compared with a spectrophotometric reference method and showed good correlation, indicating that the electrodes are suitable for food analysis.; http://www.sciencedirect.com/science/article/B6THP-4GNTFGP-2/1/087dc22044a84cfb2a1badf317934bca

Poly(ester sulphonic acid) coated mercury thin film electrodes: characterization and application in batch injection analysis stripping voltammetry of heavy metal ions

Brett, Christopher M. A.; Fungaro, Denise A.
Fonte: Universidade de Coimbra Publicador: Universidade de Coimbra
Tipo: Artigo de Revista Científica Formato: aplication/PDF
ENG
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Mercury-thin film electrodes coated with a thin film of poly(ester sulphonic acid) (PESA) have been investigated for application in the analysis of trace heavy metals by square wave anodic stripping voltammetry using the batch injection analysis (BIA) technique. Different polymer dispersion concentrations in water/acetone mixed solvent are investigated and are characterised by electrochemical impedance measurements on glassy carbon and on mercury film electrodes. The influence of electrolyte anion, acetate or nitrate, on polymer film properties is demonstrated, acetate buffer being shown to be preferable for stripping voltammetry applications. Although stripping currents are between 30 and 70% less at the coated than at bare mercury thin film electrodes, the influence of model surfactants on stripping response is shown to be very small. The effect of the composition of the modifier film dispersion on calibration plots is shown; however, detection limits of around 5 nM are found for all modified electrodes tested. This coated electrode is an alternative to Nafion-coated mercury thin film electrodes for the analysis of trace metals in complex matrices, particularly useful when there is a high concentration of non-ionic detergents.; http://www.sciencedirect.com/science/article/B6THP-3XX691V-B/1/0b3158737a56f528080be266d91c0dcb

Preparation and characterisation of poly(3,4-ethylenedioxythiophene) and poly(3,4-ethylenedioxythiophene)/poly(neutral red) modified carbon film electrodes, and application as sensors for hydrogen peroxide

Gonçalves, A. Ricardo; Ghica, M. Emilia; Brett, Christopher M. A.
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica
ENG
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Poly(3,4-ethylenedioxythiophene) (PEDOT) films have been prepared for the first time on carbon-film electrodes (CFE) in aqueous solution using electropolymerisation by potential cycling, potentiostatically and galavanostatically. Characterisation of the modified electrodes was done by cyclic voltammetry and electrochemical impedance spectroscopy and the stability of the polymer films was probed. The coated electrodes were tested for application as hydrogen peroxide sensors, by oxidation and reduction. A novel polymer film was also formed by modification of CFE by co-electropolymerisation of EDOT and the phenazine dye neutral red (NR) – (PEDOT/PNR) with a view to enhancing the properties for sensor applications. It was found that hydrogen peroxide reduction at the PEDOT/PNR coated electrodes could be carried out at a less negative potential, the sensor performance comparing very favourably with that of other polymer-modified electrodes reported in the literature.

Comparison of SERS performances of Co and Ni ultrathin films over silver to electrochemically activated Co and Ni electrodes

ANDRADE, Gustavo F. S.; BROLO, Alexandre G.; TEMPERINI, Marcia L. A.
Fonte: AMER CHEMICAL SOC Publicador: AMER CHEMICAL SOC
Tipo: Artigo de Revista Científica
ENG
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In this work, the surface-enhanced Raman scattering (SERS) spectra of pyridine (py) on thin films of Co and Ni electrodeposited on an Ag electrode activated by oxidation-reduction cycles (ORC) are presented. The SERS spectra from the thin films were compared to those of py on activated bare transition metal electrodes. It was verified that the SERS spectra of py on 3 monolayers (ML)-thick films of Ni and Co presented only bands assignable to the py adsorbed on transition metal surfaces. It was also observed that even for 50 ML-thick transition metal films, the py SERS intensity was ca. 40% of the intensity from the 3 ML-thick films. The relative intensities of the SERS bands depended on the thickness of the films, and for films thicker than 7 ML for Co and 9 ML for Ni they were very similar to those of the bare transition metal electrodes. The transition metal thin films over Ag activated electrodes presented SERS intensities 3 orders of magnitude higher than the ones from bare transition metal electrodes. These films are more suitable to study the adsorption of low Raman cross-section molecules than are ORC-activated transition metal electrodes.; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); FAPESP; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); CNPq

Uso da voltametria cíclica e da espectroscopia de impedância eletroquímica na determinação da área superficial ativa de eletrodos modificados à base de carbono; Use of cyclic voltammetry and electrochemical impedance spectroscopy for the determination of active surface area of modified carbon-based electrodes

Souza, Leticia Lopes de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 28/07/2011 PT
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Eletrodos à base de carbono, como os eletrodos de troca iônica, entre outros, têm aplicação principalmente no tratamento de efluentes industriais e rejeitos radioativos. Carbono é também amplamente utilizado em células a combustível como substrato para os eletrocatalisadores, por possuir elevada área superficial, que supera a sua área geométrica. O conhecimento desta superfície ativa total é importante na determinação das condições de operação de uma célula eletroquímica no que diz respeito às correntes a serem aplicadas (densidade de corrente). No presente estudo foram utilizadas duas técnicas eletroquímicas na determinação da área superficial ativa de eletrodos de carbono vítreo e poroso e eletrodos de troca iônica: espectroscopia de impedância eletroquímica (EIE) e voltametria cíclica (VC). Os experimentos foram realizados com soluções de KNO3 0,1 mol.L-1 em célula eletroquímica de três eletrodos: eletrodo de trabalho à base de carbono, eletrodo auxiliar de platina e eletrodo de referência de Ag/AgCl. Os eletrodos de carbono vítreo e de carbono poroso utilizado possuíam uma área geométrica de 3,14 x 10-2 cm2 e 2,83 10-1 cm2, respectivamente. O eletrodo de troca iônica foi preparado misturando-se grafite...

Eletrodos quimicamente modificados com Poli (benzil viologênio): comportamento eletroquímico de fármacos nitroderivados.; Chemically modified electrodes with Poly (benzyl viologen): electrochemical behavior of nitro derivative drugs.

Deliberto, Laíla Aparecida
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 15/03/2013 PT
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Na área da saúde, destacam-se alguns fármacos amplamente administrados, os quais possuem grupamentos nitro em suas moléculas, como o Clonazepam (CNZ), Nitrazepam (NTZ) e Nimesulida (Nimes). O CNZ e o NTZ são utilizados ilicitamente em coquetéis entorpecentes, fragilizando vítimas. A Nimes é anti-inflamatório amplamente administrado e frequentemente usado sem prescrição médica. As metodologias de detecção e quantificação destes fármacos são, na sua maioria, dispendiosas, desenvolvidas por HPLC, GC, etc. Poucos trabalhos utilizam determinação eletroanalítica e dentre eles, menos ainda utilizam eletrodos quimicamente modificados (EQMs). Os EQMs melhoram a seletividade e sensibilidade das análises. Dentre as formas de modificação, a metodologia de filmes poliméricos é muito versátil e possibilita o desenvolvimento de eletrodos específicos. Uma classe importante de polímeros é a dos derivados de viologênio, como o Poli (benzil viologênio) (PBV). Este polímero é empregado com diferentes finalidades. Possui três estados de oxidação, um deles; o PBV+ atua como mediador redox. E, a partir de experimentos prévios em nosso laboratório demonstrou ainda a possibilidade de atuar na redução de nitrocompostos. Neste sentido...

DDesenvolvimento de eletrodos modificados e métodos analíticos; Development of modified electrodes and analytical methods

Azevedo, Carla Maria Nunes
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 16/04/1999 PT
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Neste trabalho foram desenvolvidos eletrodos modificados e procedimentos para a sua utilização na determinação de diversas espécies químicas de interesse analítico, dentre as quais sulfito, ácido ascórbico, nitrito, dopamina, NADH e peróxido de hidrogênio. Foram realizados estudos envolvendo eletrodos de carbono vítreo modificados com filmes contendo uma única metaloporfirina tetrarrutenada (catiônica) e aplicações analíticas destes sensores associando-os à análise por injeção em fluxo (FIA). Estes eletrodos apresentaram efeitos catalíticos sobre a oxidação de vários analitos, intensificando o sinal de corrente e deslocando seus picos de oxidação para a região de oxidação dos átomos de Ru(II) à Ru(III), sítios ativos das porfirinas. Contudo, para a obtenção de sensores estáveis, foi necessária a utilização de uma elevada concentração do contra-íon trifluorometanossulfonato em solução, prevenindo a gradual solubilização do filme modificador. Tal dificuldade foi contornada recobrindo-se os eletrodos com filmes laminares contendo simultaneamente pares de porfirinas catiônicas e aniônicas. Estes sensores apresentaram ação catalítica igual aos eletrodos recobertos por uma única porfirina...

Comparação entre o comportamento de eletrodos revestidos utilizando dispositivos de soldagem por gravidade e com controle automático do comprimento do arco elétrico; Comparison between the behavior of covered electrodes using gravity and automatic arc length control devices

Cavalcanti, Carlos André Nobre
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Trabalho de Conclusão de Curso Formato: application/pdf
POR
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Este trabalho tem como objetivo o estudo comparativo entre o comportamento de eletrodos utilizados no processo de Soldagem a Arco com Eletrodos Revestidos (Shielded Metal Arc Welding – SMAW), utilizando um dispositivo de soldagem por gravidade e um dispositivo com controle automático do comprimento do arco elétrico. Quando se pretende caracterizar propriedades operacionais específicas de determinado tipo de eletrodo revestido, procura-se evitar a variabilidade associada à operação manual realizada pelo soldador e assegurar a repetitividade nos diversos experimentos através da utilização de dispositivos de soldagem. Tais dispositivos têm duas concepções principais: por gravidade ou com controle da tensão durante a soldagem. O presente trabalho trata da comparação do comportamento de eletrodos revestidos comerciais quando depositados com estes dois tipos de dispositivos. Para atingir este objetivo, foram projetados, fabricados e testados diferentes concepções de dispositivos de soldagem por gravidade. Foi selecionado o dispositivo mais adequado e realizada por meio deste, a deposição de cordões de solda sobre chapas de aço ao carbono utilizando eletrodos revestidos rutílicos E6013 e básicos E7018 de 3,25 mm, com diferentes correntes de soldagem. Os cordões resultantes foram avaliados através de inspeção visual...

Properties of Ca1−xHoxMnO3 perovskite-type electrodes

Ferreira, B M; Melo Jorge, M E; Lopes, M E; Nunes, M R; Silva Pereira, M I
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
ENG
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In this work, Ca1−xHoxMnO3 (x = 0, 0.1 and 0.2) perovskite oxide pelleted electrodes were prepared from the respective powders obtained by the citrate route method at 1173 K. The electrodes exhibit particle size that decreases with the holmium content in the oxide. All the samples reveal semiconductor behaviour and the presence of holmium induces a marked decrease in the electrical resistivity. The results can be well attributed to the changes in the Mn4+/Mn3+ ratio. Electrodes were characterized by cyclic voltammetry and chronopotentiometry. Cyclic voltammetric studies indicate a similar behaviour of the electrodes, irrespective of their composition. Two pairs of peaks were identified and associated, one to the Mn4+/Mn3+ redox couple and the other to the Mn7+/Mn4+ and Mn6+/Mn4+ redox couples. The voltammetric data provide evidence that the electrodes roughness factor increases with the introduction of Ho-ions in the oxide structure, what is consistent with the crystallite size obtained by X-ray diffraction (XRD) and the morphology observed by scanning electron microscopy (SEM). The Ho substituted electrodes present higher current density when compared with CaMnO3 electrodes what can be attributed both to higher electrical conductivity and smaller particle size. The chronopotentiometric studies have shown that the discharge occurs by different mechanisms for the oxide electrodes with and without Ho.

LaNiO3-based catalyst in gas diffusion electrodes: activity and stability for oxigen reactions

Silva, R. A.; Soares, C. O.; Carvalho, M. D.; Jorge, M. E. Melo; Gomes, A.; Rangel, C. M.; Pereira, M. I. da Silva
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em //2013 ENG
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Perovskite-type oxides are potential catalysts for next generation of regenerative fuel cells. In particular, LaNiO3 has been recognised as one of the most promising oxygen electrodes. In this work LaNiO3 perovskite-type oxides, prepared by a self-combustion method [1, 2], have been used for the preparation of porous gas-diffusion electrodes (GDE). Electrodes were prepared on Toray carbon paper (CP) substrates, consisting of a diffusion layer, a catalyst layer and a Nafion® layer. The gas diffusion layers were prepared using Vulcan XC-72R. The catalyst ink was prepared by suspending the material in isopropanol, stirring the mixture in an ultrasonic bath to thoroughly disperse it. Ink slurries were also pasted onto glassy carbon discs and used as working electrodes for full kinetic studies at potential domains for the oxygen reduction (ORR) and oxygen evolution (OER) reactions. A systematic study on the effect of the oxide loading (OL) on the electrodes surface area was done by cyclic voltammetry. It was found a quasi linear variation between the electrodes surface area and the oxide loading. Roughness values varying from 106±3 to 307±6 were obtained for OL between 1 and 5 mg cm-2 respectively. The results show that the peak current density increases with the increasing on oxide loading as shown in Fig. 1. Higher current densities for ORR were obtained for the electrodes prepared using LaNiO3-based perovskite with partial substitution of Ni by Cu. Stability studies of the GDEs...

Voltammetry at micro-mesh electrodes

Wadhawan,Jay D.; Welford,Peter J.; Yunus,Kamran; Fisher,Adrian C.; Compton,Richard G.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/08/2003 EN
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The voltammetry at three micro-mesh electrodes is explored. It is found that at sufficiently short experimental durations, the micro-mesh working electrode first behaves as an ensemble of microband electrodes, then follows the behaviour anticipated for an array of diffusion-independent micro-ring electrodes of the same perimeter as individual grid-squares within the mesh. During prolonged electrolysis, the micro-mesh electrode follows that behaviour anticipated theoretically for a cubically-packed partially-blocked electrode. Application of the micro-mesh electrode for the electrochemical determination of carbon dioxide in DMSO electrolyte solutions is further illustrated.

Nanoporous gold electrodes as matrices for enzyme immobilization for application in biosensors and biofuel cells

Salaj-Kośla, Urszula
Fonte: University of Limerick Publicador: University of Limerick
Tipo: info:eu-repo/semantics/doctoralThesis; all_ul_research; ul_published_reviewed; ul_theses_dissertations
ENG
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peer-reviewed; Robust nanoporous gold electrodes were fabricated by sputtering a gold-silver alloy onto a glass support and subsequent dealloying of the silver component. Alloys were prepared with either a non-uniform or uniform distribution of silver alloy which showed clear differences in morphology on characterization with scanning electron microscopy. The surface area of these electrodes was up to 28 times that of the geometric surface area. The surface area accessible to modification by redox proteins was determined using cyt c as a model system. Covalent immobilization of cyt c at SAMs modified planar and nanoporous gold electrodes resulted in ca. 9 and 11 times higher surface coverages at uniform and non-uniform nanoporous gold, respectively, than at planar gold electrodes. Well defined mediatorless bioelecytrocatalytic reduction of oxygen was obtained on nanoporous gold electrodes prepared using a vacuum method and subsequently modified with Myrthecium verrucaria bilirubin oxidase (MvBOD). Diffusion limited faradaic response, with current densities of 0.8 mA/cm2, was observed when the enzyme modified electrode was stabilized with a layer the P017-epoxy polymer. The enzyme, Trametes hirsuta laccase (ThLc) also displayes direct electron transfer at unmodified nanoporous gold electrodes. The observed current densities of ca. 0.03 mA/cm2 were 10 times higher than the current densities at the ThLc modified electrode made by drop-casting and are in contrast to the absence of a response at unmodified polycrystalline gold electrodes. Nanoporous and planar gold electrodes modified with Aspergillus niger glucose oxidase (GOx) and Corynascus thermophilus cellobiose dehydrogenase (CtCDH) together with Os redox mediators and PEGDGE as a cross-linking agent resulted in glucose and lactose detecting biosensors. The sensors had (Imax...

Information theoretic inference of the optimal number of electrodes for future cochlear implants using a spiral cochlea model

Moroz, A.S.; McDonnell, M.D.; Burkitt, A.N.; Grayden, D.B.; Meffin, H.
Fonte: IEEE Publicador: IEEE
Tipo: Conference paper
Publicado em //2012 EN
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Contemporary cochlear implants stimulate the auditory nerve with an array of up to 22 electrodes. More electrodes do not typically provide improved hearing performance. Given that this limitation is primarily due to current spread, and that newly developing kinds of electrodes may enable more focused stimulation, we recently proposed an information theoretic modeling framework for estimating how many electrodes might achieve optimal hearing performance under a range of assumptions about electrodes and their placement relative to the nerve. Here, we extend this approach by introducing more realistic three-dimensional spiral geometries for the cochlea and array, and comparing the optimal number of electrodes predicted by our model for this case with that in our original model, which used a linear geometry.; Alexey S. Moroz, Mark D. McDonnell, Anthony N. Burkitt, David B. Grayden, Hamish Meffin

Avaliação do sinal eletromiografico e da histomorfometria do musculo vasto lateral em diferentes posicionamentos de eletrodos, intensidades de contração e generos; Evaluation of the electromyographic signal and the histomorphometry of vastus lateralis muscle in different electrodes placement, intensities of contraction and genders

Fabiana Forti Sakabe
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 29/01/2010 PT
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Tem sido demonstrado que os sinais eletromiográficos e a histomorfometria diferem ao longo do ventre muscular e entre os gêneros, porém a relação entre esses parâmetros não está bem estabelecida. O objetivo deste trabalho foi avaliar a eletromiografia (EMG) em diferentes intensidades de contração (IC) isométrica voluntária (10 a 100%) e posicionamentos de eletrodos (PE) sobre o músculo vasto lateral proximal (VLP) e distal (VLD), assim como a histomorfometria em ambos os gêneros. Participaram 11 mulheres e 7 homens (22,0+2,1 e 23,3+2,5 anos, respectivamente), sem lesões nos membros inferiores. Inicialmente foi obtida uma linha de base para determinação da força máxima de extensão da perna (célula de carga MM-100 (KRATOS®)). Para a coleta da EMG foi utilizado o módulo de aquisição EMG-1000 da Lynx® (16 bits de resolução, filtro passa-banda de 20-1000 Hz e freqüência de amostragem 2000 Hz). Dois eletrodos de superfície ativos simples diferencial (Lynx®, ganho 20x) com distância intereletrodo de 10mm foram posicionados sobre o VLP e VLD. O eletrodo de referência foi fixado à tuberosidade da tíbia. O sinal foi coletado simultaneamente nos eletrodos e na célula de carga em diferentes IC por 5 segundos...

Electrodos modificados y sus aplicaciones en electrocatálisis; Nanostructured films and electrodes and their applications in electrocatalysis

Völker, Edgar
Fonte: Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires Publicador: Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires
Tipo: info:eu-repo/semantics/doctoralThesis; tesis doctoral; info:eu-repo/semantics/publishedVersion Formato: application/pdf
Publicado em //2013 SPA
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La investigación básica y aplicada en electrodos funcionalizados ha ido incrementándose en los últimos 30 años debido a su diversidad de aplicaciones en catálisis, óptica, electrónica, protección contra la corrosión, etc. Existen diversas maneras en las cuales se puede modificar un electrodo, ya sea por deposición de películas por spin o dip coating, adsorción de monocapas autoensambladas, drop casting, autoensamblado capa‐por‐capa, etc. En esta tesis estudiamos la modificación química controlada de superficies de electrodos y sus aplicaciones en reacciones electrocatalíticas y redox. Materiales diversos como Au, Cu, aleaciones Au‐Cu, polioxomolibdatos y polímeros redox fueron utilizados como electrodos funcionalizados. Estos materiales fueron caracterizados exhaustivamente y se estudiaron sus aplicaciones en reacciones electrocatalíticas de importancia en medio ambiente (reducción de CO2, nitritos, cloratos y peroxodisulfatos), así como también en reacciones redox. Durante esta tesis se desarrolló un nuevo método para la síntesis de nanoaleaciones Au‐Cu soportadas en negro de carbón. La síntesis produce nanopartículas aleadas, estables y robustas. Las nanopartículas Au‐Cu fueron caracterizadas por espectroscopía UV‐visible...

Self-supported carbon electrodes obtained by tape casting; Electrodos de carbono autosoportados obtenidos por colado en cinta

Rubio Marcos, Fernando; Villegas, Marina; Chicharro, M.; Bermejo, E.; Moreno, M.; Zapardiel, A.
Fonte: Sociedad Española de Cerámica y Vidrio Publicador: Sociedad Española de Cerámica y Vidrio
Tipo: Artículo Formato: 767510 bytes; application/pdf
ENG
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[EN] This paper describes the preparation and electrochemical response of self-supported carbon electrodes prepared by tape casting. The dc electrical conductivity, σ, of the electrodes was determined by four-wire resistance measurements and a relation between the graphite/organic additives ratio and the electrical conductivity was established. The application of these self-supported carbon electrodes as working electrodes in analytical techniques was also evaluated using norepinephrine as electroactive substance in cyclic voltammetry and chronoamperometry. The results were compared with the traditional electrodes, carbon paste electrodes (CPEs), showing that the new self-supported carbon electrodes had both lower background noise and higher analytical response.; [ES] Este artículo describe la preparación y respuesta electroquímica de electrodos de carbono autosoportados preparados mediante colado en cinta. La conductividad eléctrica en corriente continua de este nuevo tipo de electrodos de carbono se ha determinado usando el método de cuatro puntas y se ha establecido una relación ente la relación grafito/aditivos orgánicos y la conductividad eléctrica. La aplicación de estos electrodos autosoportados como electrodos de trabajo en diversas técnicas electroanalíticas también se ha evaluado...

Heterogeneously integrated impedance measuring system with disposable thin-film electrodes

Ma, Hanbin; Li, Jiahao; Cheng, Xiang; Nathan, Arokia
Fonte: Elsevier Publicador: Elsevier
Tipo: Article; accepted version
EN
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This is the accepted manuscript of a paper published in Sensors and Actuators B (Ma H, Li J, Cheng X, Nathan A, Sensors and Actuators B 2015, 21, 77?82, doi:10.1016/j.snb.2015.01.044).; We propose a novel integrated impedance measurement system with disposable thin-film electrodes. Most modern CMOS-based biosensors use on-chip electrodes to interface between the electronics and biosamples, which forces disposal of the CMOS chip after a few measurements, since most biological reactions are non-reversible. The sensor performance is also limited by the design of on-chip electrodes due to the physical dimensions and the CMOS design rules restrictions. In this work, we extract the electrodes from the silicon chip for relocation onto a low-cost, disposable substrate. This enables reusability of the high-performance CMOS chip, at the same time providing a low-cost route for manufacture of the active thin-film electrodes using large-area processing. The use of disposable thin-film chip also enables customised designed electrodes for different applications, such as extra high sensitivity concentration sensors. In this work, DNA concentration measurements are performed, and it shows a doubling of sensitivity over the previously reported system.; This work is partially supported by Isaac Newton Trust.

On damage evolution of PEM electrodes

Lugo, Melissa
Fonte: University of Delaware Publicador: University of Delaware
Tipo: Tese de Doutorado
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Karlsson, Anette M.; One of the main challenges that the polymer electrolyte membrane (PEM) fuel cell industry faces is the improvement of the durability of its fuel cells. PEMFCs are required to last for long periods of time and in order to achieve this demand, it is necessary to better understand and improve the durability of the membrane electrode assembly (MEA), which is a critical component of a PEM fuel cell. To address this issue, the failure evolution and the mechanical properties of PEM electrodes are investigated through experimental and numerical work. From an experimental point of view, the failure evolution of PEM electrodes is examined by conducting strain controlled interrupted tests. The evolution of distinct defects, such as cracks, on the surface of the electrodes is then analyzed by using scanning electron microscope. It is very important to consider the evolution of cracks observed on the electrodes, in order to capture the mechanical response of the MEA. The mechanical behavior of the MEA is obtained by conducting tensile tests at various temperature and humidity conditions. After obtaining experimental data, finite element simulations are performed by using the software ABAQUS, where the mechanical properties of "membrane A" and the electrodes are used as input. Reverse analysis is used in order to establish the mechanical properties of the electrodes that lead to the experimentally measured response of the MEA. Different cases are investigated numerically including the influence of plasticity in the electrodes...

Towards stable bifunctional oxygen electrodes and corrosion resistant gas diffusion layers for regenerative fuel cells

Silva, R. A.; Soares, C. O.; Carvalho, M. D.; Jorge, M. E. Melo; Gomes, A.; Pereira, M. I. da Silva; Rangel, C. M.
Fonte: Laboratório Nacional de Energia e Geologia Publicador: Laboratório Nacional de Energia e Geologia
Tipo: Conferência ou Objeto de Conferência
Publicado em //2013 ENG
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ABSTRACT: Regenerative fuel cells (RFCs) can provide very high energy storage at minimal weight in a dual mode system, by combining an electrolyzer and a fuel cell. Although RFCs are an appealing technology their development is still at an early stage. One key issue is the search for highly active electrocatalysts for both oxygen reduction and water oxidation. Presently, platinum is the best electrocatalyst for the oxygen reduction reaction (ORR), but has a poor oxygen evolution (OER) performance while metal oxides catalyze the OER but not the ORR. Yet, the search for the development of bi-functional oxygen electrodes is also associated to structurally stable gas diffusion layers - they must be capable of withstanding high potentials when cells are operated in the electrolyzer mode and in addition, mass transport limitations when used as a cathode in fuel cell mode. A novel approach is used in this work to tackle the issue, focussing on the development of stable gas diffusion electrodes for the oxygen reactions, having as a base high surface area LaNiO3. Previous work by the authors has optimised the synthesis of the mentioned perovskite-type oxide, prepared by a self-combustion method. The high electrochemical surface area and low porosity of the oxide has been indicated by electrochemical impedance spectroscopy (EIS) and BET measurements. A full characterization has been the subject of recent publications [1...