A influência da natureza aniônica e sua concentração na eletrodeposição de ZnO em um eletrodo de ouro de soluções de dimetilsulfóxido (DMSO) foi estudada. Experimentos voltamétricos mostraram alterações importantes no processo de eletrodeposição de óxido de zinco dependendo do ânion empregado como eletrólito. A partir de experimentos de cronoamperometria, as correspondentes curvas corrente-tempo foram ajustadas com diferentes modelos de mecanismos de nucleação e crescimento. A análise destes resultados mostrou a mudança de um crescimento instantâneo para um progressivo quando a composição da solução foi mudada de ZnCl2 para ZnCl2 + LiCl. A modificação do mecanismo está associada à adsorção de íon cloreto nos sítios ativos da superfície do eletrodo quando LiCl está presente na solução.

The influence of the anion nature and its concentration in the electrodeposition of ZnO onto a gold electrode from dimethylsulfoxide (DMSO) solutions was studied. Voltammetric experiments revealed important changes in the zinc oxide electrodeposition process depending on the employed anion as electrolyte. From chronoamperometric experiments, the corresponding current-time curves were fitted with different nucleation and growth mechanism models. The analysis of these results showed changes from an instantaneous to a progressive growth when the solution composition was changed from ZnCl2 to ZnCl2 + LiCl. The change of the mechanism is associated to the adsorption of chloride ion on the active sites of the electrode surface when LiCl is present in the solution.

In this work, we report the effect of the direct successive modifications with Glucose oxidase onto boron doped diamond electrode (BDD). The modification due to the enzyme adsorption, on the potentiodynamic response of the electrode, was evaluated using Fe(CN)6(4-/3-) red-ox couple on the electrolyte and the AEp variations were related with the number of modifications. Contact angle measurements and the electrochemical impedance spectra were also used to characterized the modifications and they showed variations in the same way that the potentiodynamic data.

Chitosan composite films were obtained from acetic or lactic acid chitosan solutions and additives such as glycerol, oleic acid, linoleic acid, polyoxyethylenesorbitan monolaureate (Tween 20) and polyoxyethylenesorbitan monooleate (Tween 80) in order to see the influence of the additive on the film formation, microstructure and morphology. The composite films obtained were observed by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) in order to evaluate the different morphology dependent upon the additives. Both SEM and AFM showed the additive influence on the rugosity and morphology of the film.

Nanostructured palladium thin films have been photochemically obtained by direct UV irradiation (254 nm) of a Pd[C8H17COCHCOC4H 9]2 amorphous film deposited on Si(100) and on ITO glass by means of the spin-coating technique. The UV photolysis of thin films of palladium b-diketonate complex results in the loss of all ligands from the coordination sphere. The acetylacetone derivative was chosen for its solid photochemistry, because the presence of branched hydrocarbons substituents lowers the intermolecular interactions, and allows the formation of high quality films upon spin-coating. The product of this photolysis was analyzed by XRD, SEM, and microanalysis. Afterwards, the film photodeposited on ITO glass was electrochemically studied, applying successive triangular scannings in a potential range of 0.00-1.30 V vs SCE for 15 minutes, in an electrolytic solution consisting in H2SO4 0.50 M. The modified electrode showed a profile similar to that of a palladium foil, although it is possible to observe that the peak potential shifts in 0.04 V approximately towards less positive values for the modified system, which is indicative of a possible catalytic effect. Based on these data, the modified ITO/Pd system was tested as an electrodic substrate for aniline polymerization in 0.10 M H2SO4; there obtaining a polymeric deposit, at lower potentials than those required when palladium foil was used as electrode, thus indicating that the method described may constitute a very interesting tool for the preparation of modified electrodes which may be advantageously used in the preparation of polymeric materials

Se han obtenido, fotoquímicamente, películas delgadas nanoestructuradas de paladio, por irradiación UV directa (254nm) de una película amorfa de Pd[C8H17COCHCOC4H 9]2 depositada sobre Si(100) y sobre vidrio ITO, mediante la técnica de spin-coating. La fotólisis de la película de complejo b-dicetonato de paladio, por luz UV, conduce a la pérdida de los ligandos de la esfera de coordinación. Los derivados de las acetilacetonas fueron escogidos por su fotoquímica en estado sólido, ya que la presencia de sustituyentes ramificados hidrocarbonados disminuye las interacciones moleculares y, mediante spin-coating, conduce a la formación de películas de alta calidad. El producto de la fotólisis fue analizado por difracción de rayos-X (XRD), microscoscopía electrónica de barrido (SEM) y microánalisis. Posteriormente, la película depositada sobre vidrio ITO se estudió eletroquímicamente, aplicando ciclos triangulares sucesivos a potenciales entre 0,00 y 1,30 V vs ECS por 15 minutos, en una disolución electrolítica de H2SO4 0,50 M. El electrodo modificado presenta un perfil similar al de una lámina de paladio, sin embargo, es posible observar en el sistema modificado un desplazamiento de los potenciales de pico, de aproximadamente 0,04 V hacia valores menos positivos, lo cual es indicativo de un posible efecto catalítico. En base a ello, el sistema modificado ITO/Pd fue usado como sustrato electródico para la polimerización de anilina en H2SO4 0,10 M, obteniéndose un deposito polimérico, a potenciales menores que los requeridos sobre la lámina de paladio, indicando que el método descrito puede consituir una interesante herramienta para la preparación de electrodos modificados, que podrían ser ventajosamente usados en la preparación de materiales poliméricos