Electrochemical and surface characterisation of carbon-film-coated piezoelectric quartz crystals

The electrochemical properties of carbon films, of thickness between 200 and 500 nm, sputter-coated on gold- and platinum-coated 6 MHz piezoelectric quartz crystal oscillators, as new electrode materials have been investigated. Comparative studies under the same experimental conditions were performed on bulk electrodes. Cyclic voltammetry was carried out in 0.1 M KCl electrolyte solution, and kinetic parameters of the model redox systems Fe(CN)(6)(3+/4+) and [Ru(NH(3))(6)](3+/2+) as well as the electroactive area of the electrodes were obtained. Atomic force microscopy was used in order to examine the surface morphology of the films, and the properties of the carbon films and the electrode-solution interface were studied by electrochemical impedance spectroscopy. The results obtained demonstrate the feasibility of the preparation and development of nanometer thick carbon film modified quartz crystals. Such modified crystals should open up new opportunities for the investigation of electrode processes at carbon electrodes and for the application of electrochemical sensing associated with the EQCM. (C) 2009 Elsevier B.V. All rights reserved.255188084809

Characterisation of poly(neutral red) modified carbon film electrodes; application as a redox mediator for biosensors

Abstract The polymer redox mediator, poly(neutral red) (PNR), has been synthesised and characterised electrochemically to investigate the best electropolymerisation and mediation conditions for application in enzyme biosensors and to clarify the mechanism of action. Neutral red was electropolymerised by potential cycling on carbon film electrode substrates by allowing the monomer to be oxidised during the full 20 cycles of polymerisation or reducing the positive limit of the potential window after the first 2 cycles to impede monomer oxidation with a view to obtaining longer polymer chains and a lesser degree of branching. Comparison was made with glassy carbon substrates. The PNR films on carbon film electrodes were characterised using cyclic voltammetry and electrochemical impedance spectroscopy, as well as in glucose biosensors prepared with PNR. Glucose oxidase enzyme was immobilised by encapsulation in silica sol-gel and compared with that obtained by cross-linking with glutaraldehyde. The biosensors were evaluated by chronoamperometry in 0.1 M phosphate buffer saline solution, pH 7.0, and showed evidence of electron transfer between the enzyme cofactor flavin adenine dinucleotide and PNR dissolved in the enzyme layer competing with PNR-mediated electrochemical degradation of H2O2 formed during the enzymatic process

Comparative Study of Different Cross-Linking Agents for the Immobilization of Functionalized Carbon Nanotubes within a Chitosan Film Supported on a Graphite−Epoxy Composite Electrode

The effectiveness of immobilization of functionalized carbon nanotubes into chitosan using different cross-linking agents has been evaluated. The cross-linkers used were glyoxal (GO), glutaraldehyde (GA), epichlorohydrin (ECH), and 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide together with N-hydroxysuccinimide (EDC-NHS), and the nanotubes were retained on graphite epoxy resin composite electrodes. The nanotube modified electrodes have been characterized by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Using CV and EIS in the presence of potassium hexacyanoferrate(III), the electroactive area of all types of electrodes was determined and the redox process analyzed, leading to the conclusion that ECH and EDC-NHS are better for immobilization of functionalized carbon nanotubes inside the chitosan matrix. The modified electrodes were successfully applied to the determination of hydrogen peroxide by fixed potential amperometry at −0.1 V vs SCE, the highest response being exhibited when using ECH

Layer-by-layer assembly for biofunctionalization of cellulosic fibers with emergent antimicrobial agents

Series title: Advances in polymer science series, ISSN 0065-3195, vol. 271Coating with polyelectrolyte multilayers has become a generic way to functionalize a variety of materials. In particular, the layer-by-layer (LbL) technique allows the coating of solid surfaces to give them several functionalities, including controlled release of bioactive agents. At present there are a large number of applications of the LbL technique; however, it is still little explored in the area of textiles. In this review we present an overview of LbL for textile materials made from synthetic or natural fibers. More specifically, LbL is presented as a method for obtaining new bioactive cotton (as in cellulosic fibers) for potential application in the medical field. We also review recent progress in the embedding of active agents in adsorbed multilayers as a novel way to provide the system with a “reservoir” where bioactive agents can be loaded for subsequent release.The authors would like to thank Fundação para a Ciência e Tecnologia (FCT) for the funding granted for the project PTDC/EBB-BIO/113671/2009 (FCOMP-01-0124-FEDER- 014752) Skin2Tex. Also, we would like to thank Fundo Europeu de Desenvolvimento Regional (FEDER) through COMPETE – Programa Operacional Factores de Competitividade (POFC) for co-funding