Highly Sensitive Neurotransmitters Analysis at Platinum-Ultramicroelectrodes Arrays

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Electroluminescence and electric current response spectroscopy applied to the characterization of polymer light-emitting electrochemical cells

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Thermal and electrochemical study of solid-state reaction of mercury with Pt-20% Rh alloy

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Utilization of electrochemical impedance spectroscopy for monitoring bornite (CU5FeS4) oxidation by Acidithiobacillus ferrooxidans

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Influence of spraying parameters on the electrochemical behaviour of HVOF thermally sprayed stainless steel coatings in 3.4% NaCl

Stainless steel coatings obtained by High Velocity Oxygen Fuel (HVOF) were characterized using optical (OM) and scanning electron microscopy (SEM), electron probe micro-analysis, X-ray diffraction (XRD), open-circuit potential (E-OC) measurements, electrochemical impedance spectroscopy (EIS) and polarisation tests. Differences among coated steels were mainly related with the gun-substrate distance parameter (310 nm for samples A and B and 260 min for C and D). The open-circuit potential values measured for all the samples after 18 h of immersion in aerated and unstirred 3.4% NaCl solution were: - 0.334, - 0.360, - 0.379 and - 0.412 V vs. Ag/AgCl,KClsat. for samples A to D, respectively. For EIS measurements, Nyquist plots showed higher capacitive semi-circle for samples sprayed at longer distance, indicating higher corrosion resistance in NaCl solution. (c) 2005 Elsevier B.V. All rights reserved.

Electrochemical impedance spectroscopy as a tool to estimate thickness in PB films

The analysis of the faradaic impedance of electroactive films provides a characteristic point from which it is possible to estimate the thickness of thin films. Thus, electrochemical impedance spectroscopy was used in this paper as a fast and easy technique to estimate this thickness. The proposed method was checked on PB films. (c) 2006 Elsevier B.V. All rights reserved.

Electrochemical capacitance spectroscopy and capacitive relaxation of the changeover process in iron hexacyanoferrate molecular compound

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Fast Screening for Antioxidant Properties of Flavonoids from Pterogyne nitens Using Electrochemical Methods

A fast, low-cost, convenient, and especially sensitive voltammetric screening approach for the study of the antioxidant properties of isoquercitrin and pedalitin from Pterogyne nitens is suggested in this work. These flavonoids were investigated for their redox properties using cyclic voltammetry in nonaqueous media using N,N-dimethylformamide and tetrabutylammonium tetrafluorborate as the supporting electrolyte, a glassy carbon working electrode, AglAgCl reference electrode, and Pt bare wire counter electrode. The comparative analysis of the activity of rutin has also been carried out. Moreover, combining HPLC with an electrochemical detector allowed qualitative and quantitative detection of micromolecules (e.g., isoquercitrin and pedalitin) that showed antioxidant activities. These results were then correlated to the inhibition of p-carotene bleaching determined by TLC autographic assay and to structural features of the flavonoids.

Studies of the Electrochemical Degradation of Acetaminophen Using a Real-Time Biomimetic Sensor

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Electrochemical Determination of Inorganic Contaminants in Automotive Fuels

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Flow injection analysis of paracetamol using a biomimetic sensor as a sensitive and selective amperometric detector

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Adsorptive potentiometric stripping analysis of nucleic acids at mercury electrodes

The application of adsorptive stripping potentiometry to the reductive detection of nucleic acids at mercury electrodes is reported. Compared to analogous voltammetric stripping modes, constant current potentiometric stripping analysis (PSA) effectively addresses the hydrogen discharge background problem, and hence greatly improves the characteristics of the superimposed cytosine/adenine (CA) reduction peak. Compared to earlier schemes for trace measurements of nucleic acids at mercury or carbon electrodes that rely on anodic signals arising from the guanine residue, convenient quantitation can now be carried out in connection with the cytosine and adenine residues. Variables influencing the adsorptive PSA response are explored and optimized. With five minute accumulation, the detection limits for tRNA, ssDNA and dsDNA are 30 mu g l(-1), 60 mu g l(-1) and 2 mg l(-1), respectively. Such different values reflect the strong dependence of the PSA CA signal upon the nucleic-acid structure. This allows the quantitation of ssDNA or tRNA in the presence of dsDNA, and offers new possibilities for electrochemical studies of DNA structure and interactions.

Electrochemical stability of SnO2-based coated Ti electrodes

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, revealed that it is relatively porous and formed by clusters of small particles. The Ti/SnO2-SbOx-RuO2 (1%) film is more compact, though. XRD analysis showed that a Sn1-xTixO2 oxide is formed on the Ti/SnO2-SbOx with 1% and without RuO2 electrodes.

Electrochemical behavior of metallic chromium in chloride media

The electrochemical behavior of metallic chromium in aqueous solutions containing chloride ions at different pH was studied by means of open-circuit potential vs. time measurements, cyclic voltammetry and electrochemical impedance spectroscopy. The composition of the surface oxides was analyzed by XPS. For solutions with pH<3 the formation of a passive layer occurs via a dissolution/precipitation process while for pH>3 the mechanism changes. XPS analysis revealed that Cr2O3 basically constitutes the passive layer.

Application of voltammetric technique to the analysis of indanthrene dye in alkaline solution

The Indanthrene Olive Green B (C.I. Vat Green 3; C.I. 69500), VG3 dye, a vat dye bearing an anthraquinonoid group and a ketonic group, can be detected by differential pulse voltammetry in alkaline solution using glassy carbon electrode. on the adsorbed form the dyes are reduced into three cathodic steps at -0.54 V, -0.65 V and -0.93 V vs Ag/AgCl. The leuco form generated after previous electrolysis at controlled potential of -1 V can be detected by voltammetry due to its reoxidation peak at -0.08 V. An analytical method is proposed for determining the vat dye using modified glassy carbon electrode by electrochemical activation in alkaline medium. Linear relationship was observed between l(Pu) vs concentration from I X 10(-5) mol L-1 to 6.0 X 10(-4) mol L-1. The detection limit was calculated to be 9.3 X 10(-6) mol L-1. (c) 2005 Elsevier Ltd. All rights reserved.