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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.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;...
An impedance study of the adsorption of nucleic acid bases at glassy carbon ele...
Oliveira-Brett, A. M.; Brett, C. M. A.; Silva, L. A.Electrochemical impedance has been used to study the adsorption at glassy carbon electrodes of guanine, its corresponding nucleoside, guanosine, and adenine. Impedance studies at different concentrations and applied potentials show clearly that all three bases are adsorbed on the electrode, blocking the surface. Irradiating the electrode with low-frequency (20 kHz) ultrasound whilst recording the impedance spec...
Spectral and electrochemical studies on blends of polyaniline and cellulose esters
Marques, A. P.; Brett, C. M. A.; Burrows, H. D.; Monkman, A. P.; Retimal, B.Blends of chemically prepared polyaniline emeraldine base (PANi) with cellulose esters were studied as films by UV-visible spectroscopy and cyclic voltammetry. The cellulose esters used were acetate, propionate, acetate butyrate, and acetate hydrogen phthalate. Films were prepared by casting from N-methylpyrrolidone or formic acid, and the effect of doping by acids on their spectral and electrochemical properti...
Influence of power ultrasound on the corrosion of aluminium and high speed steel
Morais, N. L. P. A. de; Brett, C. M. A.The influence of power ultrasound on the corrosion of aluminium and high speed steel in chloride medium has been investigated. Open circuit potential, polarization curves and electrochemical impedance spectroscopy were employed to study the corrosion process before, during and after ultrasonic irradiation as well as scanning electron microscopy of the corroded surfaces. Cavitation led to formation of pits, eros...
Influence of heat treatment on the corrosion of high speed steel
Alves, V. A.; Brett, C. M. A.; Cavaleiro, A.The corrosion behaviour of M2 high speed steel, as-received as well as heat-treated under different conditions, has been studied in 0.1 M KCl aqueous solution by corrosion potential measurements, Tafel curves and electrochemical impedance. Heat treatment leads to an increase of the corrosion resistance of high speed steel; the higher the tempering temperature after quenching, the higher the corrosion resistance...
Electrochemical behaviour of cytochrome c at electrically heated microelectrodes
Voss, T.; Gründler, P.; Brett, C. M. A.; Brett, A. M. OliveiraThe structural changes in cytochrome c with temperature have been been followed using a recently developed electrically-heated microelectrode sensor. Differential pulse voltammetry was used to perform electrochemical measurements of cytochrome c oxidation at different temperatures at heated bare gold electrodes contained in phosphate-buffered cytochrome c solution at room temperature. The voltammetric response ...
Use of ultramicroindentation to evaluate the degradation of sputtered coatings
Cavaleiro, A.; Louro, C.; Fernandes, J. V.; Brett, C. M. A.The aim of this research work was to study the influence of chemical degradation on the mechanical properties of the non-degraded zones of sputtered W-N-Ti coatings. For this, an ultramicroindentation technique has been used before and after degradation, either on the zones between the pits in the corroded samples, or on the non-oxidised layers after removal of the top degraded layers. By using different applie...
Influence of anions on the corrosion of high speed steel
Brett, C. M. A.; Melo, P. I. C.Corrosion potential measurements, voltammetric techniques and electrochemical impedance have been used to evaluate the corrosion resistance of M2 high speed steel in aqueous solutions containing chloride, bromide, iodide, nitrate, sulfate and perchlorate salts of sodium and potassium of varying concentration. The influence of changing the cation was found to be small and an order of anion aggressivity was estab...
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