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Effect of cerium (IV) ions on the anticorrosion properties of siloxane-poly(methyl methacrylate) based film applied on tin coated steel

SUEGAMA, P. H.; SARMENTO, V. H. V.; MONTEMOR, M. F.; BENEDETTI, A. V.; MELO, H. G. de; AOKI, I. V.; SANTILLI, C. V.
Fonte: PERGAMON-ELSEVIER SCIENCE LTD Publicador: PERGAMON-ELSEVIER SCIENCE LTD
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
56.26%
This work investigates the influence of the addition of cerium (IV) ions on the anticorrosion properties of organic-inorganic hybrid coatings applied to passivated tin coated steel. In order to evaluate the specific effect of cerium (IV) addition on nanostructural features of the organic and inorganic phases of the hybrid coating, the hydrolytic polycondensation of silicon alkoxide and the radical polymerization of the methyl methacrylate (MMA) function were induced separately. The corrosion resistance of the coatings was evaluated by means of linear polarization, Tafel type curves and electrochemical impedance measurements. The impedance results obtained for the hybrid coatings were discussed based on an electrical equivalent circuit used to fit the experimental data. The electrochemical results clearly showed the improvement of the protective properties of the organic-inorganic hybrid coating mainly when the cerium (IV) was added to the organic phase solution precursor, which seemed to be due to the formation of a more uniform and densely reticulated siloxane-PMMA film. (C) 2010 Elsevier Ltd. All rights reserved.; FAPESP[05/51851-4]; FAPESP[07/53073-4]; CNPq[310860/2005-9]; CNPq[300728/2007-7]; CNPq[305073/2008-7]; CAPES[BEX-3167-08-9]

Electrochemical study of modified non-functional bis-silane layers on Al alloy 2024-T3

PALOMINO, Luis M.; SUEGAMA, Patricia H.; AOKI, Idalina V.; MONTEMOR, M. Fatima; MELO, Hercilio G. De
Fonte: PERGAMON-ELSEVIER SCIENCE LTD Publicador: PERGAMON-ELSEVIER SCIENCE LTD
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
56.22%
In the last few years great efforts have been made in order to find and to develop environmentally friendly substitutes for Cr6+ pre-treatments applied on aluminium alloys used in the aircraft industry. Among the potential substitutes, silane layers have attracted considerable interest from researchers and from the industry. The present work investigates the anti-corrosion behaviour of (bis-1, 2-(triethoxysilyl) ethane (BTSE)) silane layers modified with Ce ions and/or silica nanoparticles applied on Al alloy 2024-T3 substrates. The corrosion behaviour was investigated in 0.1 M NaCl solution via d.c. polarization and electrochemical impedance spectroscopy (EIS). Contact angle measurements and XPS were used to assess information on the chemistry of the silane pre-treated surfaces. The results have shown that the introduction of additives improves the corrosion protection properties of the silane layer. (c) 2008 Elsevier Ltd. All rights reserved.

In situ impedance spectroscopy study of the electrochemical corrosion of Ti and Ti-6Al-4V in simulated body fluid at 25 degrees C and 37 degrees C

ALVES, V. A.; REIS, R. Q.; SANTOS, I. C. B.; SOUZA, D. G.; GONCALVES, T. de F.; SILVA, Marcelo de Assumpção Pereira da; ROSSI, A.; SILVA, L. A. da
Fonte: PERGAMON-ELSEVIER SCIENCE LTD Publicador: PERGAMON-ELSEVIER SCIENCE LTD
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
56.22%
The corrosion resistance of Ti and Ti-6Al-4V was investigated through electrochemical impedance spectroscopy, EIS, potentiodynamic polarisation curves and UV-Vis spectrophotometry. The tests were done in Hank solution at 25 degrees C and 37 degrees C. The EIS measurements were done at the open circuit potential at specific immersion times. An increase of the resistance as a function of the immersion time was observed, for Ti (at 25 degrees C and 37 degrees C), and for Ti-6Al-4V (at 25 degrees C), which was interpreted as the formation and growth of a passive film on the metallic surfaces. (C) 2009 Elsevier Ltd. All rights reserved.; Financiadora de Estudos e Projetos (FINEP); FINEP[01.06.0243.00]; FAPEMIG[CDS 12/03]; Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG); FAPEMIG[CEX 1736/06]; Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG); CNPq[520178/2006-8]; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Effects of thickness coating on the electrochemical behaviour of thermal spray Cr3C2-NiCr coatings

Guilemany, J. M.; Fernandez, J.; Delgado, J.; Benedetti, A. V.; Climent, F.
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 107-113
ENG
Relevância na Pesquisa
56.23%
Thermally sprayed HVOF coatings are increasingly being used in industrial applications where high wear and corrosion resistance are needed [1,2]. In this paper, electrochemical ac and de experiments were used in order to obtain the corrosion resistance of coated steel with different numbers of Cr3C2-NiCr layers. This work has been performed in order to determine the role of coating thickness in the corrosion behaviour of a steel protected with cermet thermally sprayed coatings. It is known that a thicker layer protects better against corrosion when a metallic coating is evaluated. But cermet coatings, such as Cr3C2-NiCr, contain higher levels of porosity and residual stresses than metallic coatings, which really could influence the corrosion resistance of the deposited layer. Electrochemical measurements, such as Open-Circuit Potential (E-Osubset of), Polarisation Resistance (RP) and Cyclic Voltammetry (CV), were performed in an aerated 3.4 NaCI media (%wt.). Electrochemical Impedance Measurements (EIS) were also done in order to obtain a mechanism that explains the corrosion process. Structural Characterisation was carried out by means of Optical and Scanning Electron Microscopes (OM, SEM) with an Energy Dispersive Spectrometry analyser (EDS). Results show that the corrosion resistance of the complete system is mainly influenced by the substrate behaviour. The application of a higher number of deposited layers did not substantially increase their anticorrosive properties. Stress generation during the spraying deposition process plays an important role in the behaviour of the coated steel against corrosion phenomena. (C) 2002 Elsevier B.V. B.V All rights reserved.

Resistência à corrosão das fases presentes em amálgamas dentários

Acciari, Heloisa Andréa; Guastaldi, Antonio Carlos; Brett, Christopher M. A.
Fonte: Editora Unesp Publicador: Editora Unesp
Tipo: Artigo de Revista Científica Formato: 125-142
POR
Relevância na Pesquisa
56.2%
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Neste trabalho avaliou-se a resistência à corrosão em solução salina das fases presentes na microestrutura de amálgamas dentários comerciais: gama1-Ag2Hg3, o eutético Ag-Cu e gama2-Sn7-8Hg, empregando-se técnicas eletroquímicas de potencial a circuito aberto com o tempo, de polarização potenciodinâmica e de espectroscopia de impedância eletroquímica. As ligas metálicas em estudo já foram caracterizadas em um trabalho prévio, por meio de microscopia eletrônica de varredura e difratometria de raios X. A resistência à corrosão se origina da formação de filmes passivos na superfície metálica e parece estar determinada pela natureza rugosa e porosa das superfícies.; In this work, the corrosion resistance behavior of three of their phases presents in dental amalgam has been investigated: gamma1-Ag2Hg3 (the matrix phase in the microstructure), gamma2-Sn7-8Hg (the phase most susceptible to corrosion in the oral cavity, according to the literature) and Ag-Cu eutectic (the component of the more modern powder alloys, the objective being to reduce the quantity of gamma2-Sn7-8Hg formed during the amalgamation and in this way increase its corrosion resistance). Electrochemical measurements were carried out in 0...

Optimization of incubation time of protein Tc85 in the construction of biosensor: Is the EIS a good tool?

Pupim Ferreira, Antonio Ap.; Alves, Maria Julia M.; Barrozo, S.; Yamanaka, Hideko; Benedetti, Assis Vicente
Fonte: Elsevier B.V. Sa Publicador: Elsevier B.V. Sa
Tipo: Artigo de Revista Científica Formato: 1-8
ENG
Relevância na Pesquisa
56.2%
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Processo FAPESP: 05/50734-4; Electrochemical impedance spectroscopy (EIS) in pH 6.9 phosphate buffer solution was used to investigate each step of the procedure employed to modify a screen-printed electrode (SPE). The SPE was modified with self-assembled monolayers (SAMs) of cystamine (CYS, deposited from 20 mM solution), followed by glutaraldehyde (GA, 0.3 M solution). The Trypanosoma cruzi antigen was immobilized using different deposition times. The influence of incubation time (2-18 h) of protein was also investigated. The topography of modified electrode with this protein was investigated by atomic force microscopy (AFM). Interpretation of impedance data was based on physical and chemical adsorption, and degradation of the layer at high and meddle frequencies, and charge transfer reaction involving mainly the reduction of oxygen at low frequencies. EIS studies on modified electrodes with Tc85 protein immobilized for different incubation times indicated that the optimum incubation time was 6-8 h. It was demonstrated that EIS is a good technique to evaluate the different steps and the integrity of the surface modifications...

Electrochemical stability of SnO2-based coated Ti electrodes

Fugivara, C. S.; Paiva-Santos, C. O.; Benedetti, A. V.; Modiano, S.; Sumodjo, PTA; Walton, C. W.; Rudd, E. J.
Fonte: Electrochemical Society Inc Publicador: Electrochemical Society Inc
Tipo: Conferência ou Objeto de Conferência Formato: 39-49
ENG
Relevância na Pesquisa
56.23%
The electrochemical behavior of SnO2-SbOx, based electrodes, with and without the addition of RuO2, was studied by cyclic voltammetry, service life measurements and electrochemical impedance spectroscopy in 0.5 M H2SO4 the physical characteristics of these materials were investigated using SEM, EDX and XRD. The resulting cyclic voltammograms obtained using SnO2-SbOx, and SnO2-SbOx-RuO2(x), x = 30, 5, 1 and 0.4 % showed that the OER overpotential decreased with the addition of RuO2. In the repetitive triangular potential voltammetry applied to the SnO2 electrode without and with RuO2 (1%), a higher anodic current is observed during the first potential scan; it is explained in terms of the oxidation of the Ti substrate. The addition of 1% RuO2 increased the service life from 8 to 20 hours at 10 mAcm(-2), while at 50 mAcm(-2) this increase was from 1 to 8 hours. AC Impedance diagrams obtained for the Ti/SnO2-SbOx and Ti/SnO2-SbOx-RuO2 electrodes at the rest potential and at a potential in the OER region can be explained by a single equivalent circuit containing two elements in series. The results showed that the charge transfer resistance and the resistance of the oxide film are lower in the oxide film containing RuO2. Surface analysis of Ti/SnO2-SbOx...

Gamma phases in Cu-Al alloys and the influence of a square shaped phase in the electrochemical behavior of a Cu-13.6wt% Al alloy

Hurtado, MRF; Ferrer, J. C.; Adorno, A. T.; Sumodjo, PTA; Benedetti, A. V.; Natishan, P. M.; Isaacs, H. S.; JanikCzachor, M.; Macagno, V. A.; Marcus, P.; Seo, M.
Fonte: Electrochemical Society Inc Publicador: Electrochemical Society Inc
Tipo: Conferência ou Objeto de Conferência Formato: 665-676
ENG
Relevância na Pesquisa
56.23%
The electrochemical behavior of Cu-xAl alloys, with 11 wt%less than or equal to x less than or equal to 15wt%, in 0.5 M H2SO4 was studied by means of open-circuit potential decay measurements, quasi-stationary and fast cyclic voltammetry, and electrochemical impedance spectroscopy. Some of the alloys (x less than or equal to 14%), when quenched formed martensitic structures. Alloys with greater than or equal to 13% showed a little square-shaped phase when quenched from temperatures around 800 degrees C. It was observed that in sulfuric medium, these formations were dealuminized differently than the martensitic phase. The values of the rest potentials are more influenced by the heat treatment rather than by the alloy composition. An anodic Tafel slope of ca. 60 mV/decade was observed for all the alloys, independently of the heat treatment. This is explained in terms of a competition between two processes: copper oxidation and copper(I) deproportionation. In the cyclic voltammetric experiments it was observed an anodic current peak, related with copper oxidation with a possible formation of some interfacial species, and a cathodic current peak during the reverse potential scan, associated with the reduction of soluble species and/or of the film. The AC Impedance data were interpreted in terms of electric equivalent circuits.

Comparing label free electrochemical impedimetric and capacitive biosensing architectures

Fernandes, Flavio C. B.; Santos, Adriano; Martins, Denise C.; Goes, Marcio S.; Bueno, Paulo R.
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 96-102
ENG
Relevância na Pesquisa
56.22%
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); The transducer faradaic signals of molecularly receptive interfaces associated with specific target binding can be sensitively monitored by electrochemical impedance and/or capacitance spectroscopies. A comparative evaluation of both impedimetric (associated with charge transfer resistance) and capacitive (associated with faradaic density of states) approaches was undertaken using C-reactive protein (CRP) antigen and antibody interaction as biomolecular binding model. Aiming at constructing redox free (impedimetric) and redox tethered receptive (capacitive) interfaces engineered by self-assembly monolayer, CRP sensitivity and limit of detections were comparatively assessed regarding biosensor capabilities. Binding affinity constant between CRP and anti-CRP interfacial receptor sites were additionally evaluated by the Langmuir adsorption model. Both the impedimetric and capacitive approaches reported similar values of experimental analytical parameters albeit the latter was found to have the advantage of requiring no solution redox reporter thus making it highly suitable for use in multiplexing affinity arrays. (C) 2014 Elsevier B.V. All rights reserved.

AC Impedance Spectroscopy of Native DNA and M-DNA

Long, Yi-Tao; Li, Chen-Zhong; Kraatz, Heinz-Bernhard; Lee, Jeremy S.
Fonte: Biophysical Society Publicador: Biophysical Society
Tipo: Artigo de Revista Científica
Publicado em /05/2003 EN
Relevância na Pesquisa
56.22%
Monolayers of thiol-labeled DNA duplexes of 15, 20, and 30 basepairs were assembled on gold electrodes. Electron transfer was investigated by electrochemical impedance spectroscopy with Fe(CN)63−/4− as a redox probe. The spectra, in the form of Nyquist plots, were analyzed with a modified Randles circuit which included an additional component in parallel, Rx, for the resistance through the DNA. For native B-DNA Rx and Rct, the charge transfer resistance, both increase with increasing length. M-DNA was formed by the addition of Zn2+ at pH 8.6 and gave rise to characteristic changes in the Nyquist plots which were not observed upon addition of Mg2+ or at pH 7.0. Rx and Rct also increased with increasing duplex length for M-DNA but both were significantly lower compared to B-DNA. Therefore, electron transfer via the metal DNA film is faster than that of the native DNA film and certain metal ions can modulate the electrochemical properties of DNA monolayers. The results are consistent with an ion-assisted long-range polaron hopping mechanism for electron transfer.

Impedance-Based Monitoring of Ongoing Cardiomyocyte Death Induced by Tumor Necrosis Factor-α

Qiu, Yiling; Liao, Ronglih; Zhang, Xin
Fonte: The Biophysical Society Publicador: The Biophysical Society
Tipo: Artigo de Revista Científica
Publicado em 04/03/2009 EN
Relevância na Pesquisa
56.23%
Deregulated cardiomyocyte death is a critical risk factor in a variety of cardiovascular diseases. Although various assays have been developed to detect cell responses during cell death, the capability of monitoring cell detachment will enhance the understanding of death processes by providing instant information at its early phase. In this work, we developed an impedance-sensing assay for real-time monitoring of cardiomyocyte death induced by tumor necrosis factor-α based on recording the change in cardiomyocyte adhesion to extracellular matrix. Electrochemical impedance spectroscopy was employed in impedance data processing, followed by calibration with the electrical cell-substrate impedance-sensing technique. The adhesion profile of cardiomyocytes undergoing cell death processes was recorded as the time course of equivalent cell-substrate distance. The cell detachment was detected with our assay and proved related to cell death in the following experiments, indicating its advantage against the conventional assays, such as Trypan blue exclusion. An optimal concentration of tumor necrosis factor-α (20 ng/mL) was determined to induce cardiomyocyte apoptosis rather than the combinative cell death of necrosis and apoptosis by comparing the concentration-related adhesion profiles. The cardiomyocytes undergoing apoptosis experienced an increase of cell-substrate distance from 59.1 to 89.2 nm within 24 h. The early change of cell adhesion was proved related to cardiomyocyte apoptosis in the following TUNEL test at t = 24 h...

Pseudomonas aeruginosa Can Be Detected in a Polymicrobial Competition Model Using Impedance Spectroscopy with a Novel Biosensor

Ward, Andrew C.; Connolly, Patricia; Tucker, Nicholas P.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 10/03/2014 EN
Relevância na Pesquisa
56.25%
Electrochemical Impedance Spectroscopy (EIS) is a powerful technique that can be used to elicit information about an electrode interface. In this article, we highlight six principal processes by which the presence of microorganisms can affect impedance and show how one of these - the production of electroactive metabolites - changes the impedance signature of culture media containing Pseudomonas aeruginosa. EIS, was used in conjunction with a low cost screen printed carbon sensor to detect the presence of P. aeruginosa when grown in isolation or as part of a polymicrobial infection with Staphylococcus aureus. By comparing the electrode to a starting measurement, we were able to identify an impedance signature characteristic of P. aeruginosa. Furthermore, we are able to show that one of the changes in the impedance signature is due to pyocyanin and associated phenazine compounds. The findings of this study indicate that it might be possible to develop a low cost sensor for the detection of P. aeruginosa in important point of care diagnostic applications. In particular, we suggest that a development of the device described here could be used in a polymicrobial clinical sample such as sputum from a CF patient to detect P. aeruginosa.

Stretchable Electrochemical Impedance Sensors for Intravascular Detection of Lipid-Rich Lesions in New Zealand White Rabbits

Cao, Hung; Yu, Fei; Zhao, Yu; Scianmarello, Nick; Lee, Juhyun; Dai, Wangde; Jen, Nelson; Beebe, Tyler; Li, Rongsong; Ebrahimi, Ramin; Chang, Donald S.; Mody, Freny V.; Pacella, John; Tai, Yu-Chong; Hsiai, Tzung
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
56.24%
Flexible electronics have enabled catheter-based intravascular sensing. However, real-time interrogation of unstable plaque remains an unmet clinical challenge. Here, we demonstrate the feasibility of stretchable electrochemical impedance spectroscopy (EIS) sensors for endoluminal investigations in New Zealand White (NZW) rabbits on diet-induced hyperlipidemia. A parylene C (PAC)-based EIS sensor mounted on the surface of an inflatable silicone balloon affixed to the tip of an interrogating catheter was deployed 1) on the explants of NZW rabbit aorta for detection of lipid-rich atherosclerotic lesions, and 2) on live animals for demonstration of balloon inflation and EIS measurements. An input peak-to-peak AC voltage of 10 mV and sweeping-frequency from 300 kHz to 100 Hz were delivered to the endoluminal sites. Balloon inflation allowed EIS sensors to be in contact with endoluminal surface. In the oxidized low-density-lipoprotein (oxLDL)-rich lesions from explants of fat-fed rabbits, impedance magnitude increased significantly by 1.5-fold across the entire frequency band, and phase shifted ~5 degrees at frequencies below 10 kHz. In the lesion-free sites of the normal diet-fed rabbits, impedance magnitude increased by 1.2-fold and phase shifted ~5 degrees at frequencies above 30 kHz. Thus...

Obtenção e caracterização físico-química de blendas poliméricas, baseadas em POE e PMMA, dopadas com dióxido de titânio

Lima, Elias Januário de
Fonte: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Química; Físico-Química; Química Publicador: Universidade Federal do Rio Grande do Norte; BR; UFRN; Programa de Pós-Graduação em Química; Físico-Química; Química
Tipo: Dissertação Formato: application/pdf
POR
Relevância na Pesquisa
56.22%
The study of polymer blends has been an alternative method in the search field of new materials for obtaining materials with improved properties. In this work blends of poly(methyl methacrylate) (PMMA) and poly(ethylene oxide) (PEO) doped with titanium dioxide (TiO2) were studied. The PEO is a polymer semicrystalline structure varying between, 70 and 84% crystallinity, while the PMMA exhibits behavior amorphous in their structure. The use of TiO2 is related to corrosion-resistant of titanium as well as good heat transfer and other characteristics. The study of these polymer blends doped TiO2 gives the properties junction organic (polymer) and inorganic (oxide) which leads to modification of the properties of the resultant material. The blends were doped TiO2 (POE/PMMA/TiO2) in different proportions of the PMMA with the PEO and TiO2 fixed. The ratios were: 90/10/0,1; 85/15/0, 1; 80/20/0,1, 75/25/0,1 and 70/30/0,1. The resulting material was obtained in powder form and being characterized by Fourier Transformed Infrared (FTIR) Spectroscopy, Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), Thermogravimetric Analysis (TGA) and Electrochemical Impedance Spectroscopy (EIS). The infrared spectra (IR) for the blends in different ratios showed a band at 1744 cm-1...

Síntese e caracterização de filmes de óxidos metálicos nanoparticulados para aplicação em células solares sensibilizadas por corante (DSCs)

Paula, Leonardo Ferreira de
Fonte: Universidade Federal de Uberlândia Publicador: Universidade Federal de Uberlândia
Tipo: Dissertação
POR
Relevância na Pesquisa
56.22%
Neste trabalho foram preparados filmes finos e compactos de óxidos nanoparticulados de TiO2, Nb2O5 e WO3 para a aplicação como camada de contato/bloqueio em células solares sensibilizadas por corante (DSCs). Os filmes foram produzidos pela deposição de 30 bicamadas de TiO2(ác)/TiO2(bás), TiO2(ác/Nb2O5(bás) e TiO2(ác)/WO3(bás) utilizando a técnica de automontagem (Layer-by-Layer ou LbL), a partir dos sóis nanoparticulados de TiO2 (pH = 2 e 10), Nb2O5 (pH = 10) e WO3 (pH = 10) sintetizados pelo método sol-gel. A presença das bicamadas de TiO2/TiO2, TiO2/Nb2O5 gerou aumentos relativos na eficiência das DSCs de 25% e 87% respectivamente, quando comparadas às DSCs sem as bicamadas. Já o filme de TiO2/WO3 não gerou nenhuma melhoria na eficiência das DSCs. Fatores como a espessura, homogeneidade das nanopartículas, concentração dos óxidos nos filmes e a rugosidade influenciam diretamente na eficiência dos filmes como camada de contato/bloqueio. Imagens de Microscopia Eletrônica de Varredura com Emissão de Campo (MEV-FEG) e Microscopia de Força Atômica (MFA) confirmaram que todos os filmes apresentaram nanopartículas esféricas com diâmetros homogêneos e menores que 20 nm, o que acarreta na formação de superfícies compactas e pouco porosas. Esta morfologia garante uma barreira física entre o eletrólito e a superfície do vidro condutor utilizado como eletrodo nas DSCs. Os filmes de TiO2/TiO2 e TiO2/Nb2O5 apresentaram também rugosidades maiores que a da superfície do vidro condutor sem as bicamadas...

Impedance nanopore biosensor: influence of pore dimensions on biosensing performance

Kant, K.; Yu, J.; Priest, C.; Shapter, J.; Losic, D.
Fonte: Royal Society of Chemistry Publicador: Royal Society of Chemistry
Tipo: Artigo de Revista Científica
Publicado em //2014 EN
Relevância na Pesquisa
56.26%
Knowledge about electrochemical and electrical properties of nanopore structures and the influence of pore dimensions on these properties is important for the development of nanopore biosensing devices. The aim of this study was to explore the influence of nanopore dimensions (diameter and length) on biosensing performance using non-faradic electrochemical impedance spectroscopy (EIS). Nanoporous alumina membranes (NPAMs) prepared by self-ordered electrochemical anodization of aluminium were used as model nanopore sensing platforms. NPAMs with different pore diameters (25–65 nm) and lengths (4–18 μm) were prepared and the internal pore surface chemistry was modified by covalently attaching streptavidin and biotin. The performance of this antibody nanopore biosensing platform was evaluated using various concentrations of biotin as a model analyte. EIS measurements of pore resistivity and conductivity were carried out for pores with different diameters and lengths. The results showed that smaller pore dimensions of 25 nm and pore lengths up to 10 μm provide better biosensing performance.; Krishna Kant, Jingxian Yu, Craig Priest, Joe G. Shapter and Dusan Losic

Impedance Spectroscopy of Zirconium Alloys

MACAK Jan; NOVOTNY Radek; SAJDL Petr; CERNOUSEK Tomas; VRTILKOVA Vera
Fonte: EUROCORR Publicador: EUROCORR
Tipo: Contributions to Conferences Formato: CD-ROM
ENG
Relevância na Pesquisa
56.23%
Corrosion of different types or zirconium alloys was investigated in-situ under high pressure high temperature conditions using electrochemical impedance spectroscopy. Long-term experiments were performed under VVER simulating conditions at 290o and 340o. Experimental impedance spectra were typical by presence of two time constant. High frequency one was identified as being related to electric transfer properties of the oxide layer formed in high temperature electrolyte. The low frequency time constant was connected with kinetic and mass transfer phenomena. Impedance spectra were processed using different models and the parameters of impedance models were compared with data obtained by independent analysis. Optimal model was selected and parameters characterizing time evolution of oxide parameters and kinetic and mass transfer parameters of zirconium alloys corrosion were obtained.; JRC.DDG.F.4-Safety of future nuclear reactors

Projeto e fabricação de um sistema sensor de espectroscopia de impedância eletroquímica; Design and fabrication of an electrochemical impedance spectroscopy sensor system

Erasmo José Dias Chiappetta Filho
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 18/06/2015 PT
Relevância na Pesquisa
56.22%
o Resumo poderá ser visualizado no texto completo da tese digital.; The Abstract is available with the full electronic digital document.

A Realtime and Continuous Assessment of Cortisol in ISF Using Electrochemical Impedance Spectroscopy

Venugopal, Manju; Arya, Sunil K.; Chornokur, Ganna; Bhansali, Shekhar
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 01/12/2011 EN
Relevância na Pesquisa
56.26%
This study describes the functioning of a novel sensor to measure cortisol concentration in the interstitial fluid (ISF) of a human subject. ISF is extracted by means of vacuum pressure from micropores created on the stratum corneum layer of the skin. The pores are produced by focusing a near infrared laser on a layer of black dye material attached to the skin. The pores are viable for approximately three days after skin poration. Cortisol measurements are based on electrochemical impedance (EIS) technique. Gold microelectrode arrays functionalized with Dithiobis (succinimidyl propionate) self-assembled monolayer (SAM) have been used to fabricate an ultrasensitive, disposable, electrochemical cortisol immunosensor. The biosensor was successfully used for in-vitro measurement of cortisol in ISF. Tests in a laboratory setup show that the sensor exhibits a linear response to cortisol concentrations in the range 1 pm to 100 nM. A small pilot clinical study showed that in-vitro immunosensor readings, when compared with commercial evaluation using enzyme-linked immunoassay (ELISA) method, correlated well with cortisol levels in saliva and ISF. Further, circadian rhythm could be established between the subject's ISF and the saliva samples collected over 24 hours time-period. Cortisol levels in ISF were found reliably higher than in saliva. This Research establishes the feasibility of using impedance based biosensor architecture for a disposable...

Electrochemical Impedance Spectroscopy of Ni-B Coatings and Optimization by Taguchi Method and Grey Relational Analysis

Das,Suman K.; Sahoo,Prasanta
Fonte: Sociedade Portuguesa de Electroquímica Publicador: Sociedade Portuguesa de Electroquímica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2011 EN
Relevância na Pesquisa
56.22%
Electroless nickel coatings possess several advantages over electroplating such as ability to coat any material and with uniform thickness. Besides, these coatings are used mainly for their wear resistance and corrosion resistance applications. The present study addresses the corrosion behavior of the coating based on electrical impedance spectroscopy. The effect of the four parameters viz. bath temperature, reducing agent concentration, nickel source concentration and annealing temperature, on the electrochemical characteristics (charge transfer resistance and double layer capacitance) are studied with the help of Taguchi method and grey relational analysis. It is found that the bath temperature has the most significant influence on the corrosion behavior of the coating followed by nickel source concentration. The microstructural characterization of the coating is done with the help of scanning electron microscope, X-ray diffraction analysis and energy dispersive X-ray analysis.