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J Nanosci Nanotechnol ; 9(4): 2346-52, 2009 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-19437974


Multiwalled carbon nanotubes were entrapped in sol-gel processed hydrophilic silicate thin film on tin-doped indium oxide support. Microscopic images show that the nanotubes form large agglomerates of largely separated nanotubes covered by silicate film. The measurements of capacitive current prove that approximately 10% of them remain electrochemically active. The surface confined cyclic voltammetry indicate adsorption of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) on this material. The oxidation charge estimated after the adsorption saturated shows that this compound is adsorbed on almost all the surface of the immobilised carbon nanotubes. After further modification of the electrode with extracellular laccase from Cerrena unicolor electrocatalytic dioxygen reduction is observed. The immobilised enzyme exhibits catalytic action whereas 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonate) adsorbed on carbon nanotubes serves as electron mediator between protein and electrode. Bioelectrocatalysis is also observed in the absence of adsorbed mediator but the efficiency of the process is approximately one order of magnitude smaller.

Benzotiazóis/química , Técnicas Biossensoriais/métodos , Lacase/metabolismo , Nanotubos de Carbono/química , Oxigênio/metabolismo , Silicatos/química , Ácidos Sulfônicos/química , Adsorção , Enzimas Imobilizadas/química , Enzimas Imobilizadas/metabolismo , Lacase/química , Oxirredução
Chem Commun (Camb) ; (23): 2954-6, 2005 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-15957037


Ion transfer across the boundary formed at an ionic liquid drop deposited on an electrode immersed in aqueous solution, generated by electrochemical redox reaction at the electrode-ionic liquid interface, is studied to obtain information about the ability of anions to be transferred into a room temperature ionic liquid.

Analyst ; 129(12): 1181-5, 2004 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-15565215


Hydrophobic sol-gel films from methyltrimethoxysilane (MTMOS) are deposited onto glass and tin-doped indium oxide (ITO) coated glass substrates. Uniform and microporous films of ca. 200 nm thickness are obtained and investigated by scanning electron microscopy and by electrochemical techniques. From cyclic voltammograms for the oxidation of ferrocenedimethanol in aqueous 0.1 M KNO3 apparent diffusion coefficients and free volume data for processes within the film are derived and it is demonstrated that the film morphology can be controlled by the deposition timing. Two novel types of biphasic electrodes for observing liquid/liquid ion transfer reactions are introduced: (i) an ITO electrode coated with a hydrophobic sol-gel film and (ii) a hydrophobic sol-gel film on glass sputter-coated with 20 nm porous gold (porotrode). For the t-butylferrocene redox system deposited in the form of an organic liquid, very low and morphology dependent current responses are observed on modified ITO electrodes. However, the porotrode system allows biphasic electrode reactions to be driven with high efficiency and with no significant morphology effect of the hydrophobic sol-gel film. This type of nanofilm-modified electrode system will be of interest for biphasic sensor developments.