by Keyword: Cyclic voltammetry

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Hoyo, J., Guaus, E., Torrent-Burgués, J., Sanz, F., (2015). Electrochemistry of LB films of mixed MGDG: UQ on ITO Bioelectrochemistry 104, 26-34

The electrochemical behaviour of biomimetic monolayers of monogalactosyldiacylglycerol (MGDG) incorporating ubiquinone-10 (UQ) has been investigated. MGDG is the principal component in the thylakoid membrane and UQ seems a good substitute for plastoquinone-9, involved in photosynthesis chain. The monolayers have been performed using the Langmuir and Langmuir-Blodgett (LB) techniques and the redox behaviour of the LB films, transferred at several surface pressures on a glass covered with indium-tin oxide (ITO), has been characterized by cyclic voltammetry. The cyclic voltammograms show that UQ molecules present two redox processes (I and II) at high UQ content and high surface pressures, and only one redox process (I) at low UQ content and low surface pressures. The apparent rate constants calculated for processes I and II indicate a different kinetic control for the reduction and the oxidation of UQ/UQH2 redox couple, being kRapp(I)=2.2·10-5s-1, kRapp(II)=5.1·10-14 kOapp(I)=3.3·10-3s-1 and kOapp(II)=6.1·10-6s-1, respectively. The correlation of the redox response with the physical states of the LB films allows determining the positions of the UQ molecules in the biomimetic monolayer, which change with the surface pressure and the UQ content. These positions are known as diving and swimming.

Keywords: Cyclic voltammetry, Electron transfer, Langmuir-Blodgett film, Modified ITO electrode, Monogalactosyldiacylglycerol, Ubiquinone

Tahirbegi, I. B., Alvira, M., Mir, M., Samitier, J., (2014). Simple and fast method for fabrication of endoscopic implantable sensor arrays Sensors 14, (7), 11416-11426

Here we have developed a simple method for the fabrication of disposable implantable all-solid-state ion-selective electrodes (ISE) in an array format without using complex fabrication equipment or clean room facilities. The electrodes were designed in a needle shape instead of planar electrodes for a full contact with the tissue. The needle-shape platform comprises 12 metallic pins which were functionalized with conductive inks and ISE membranes. The modified microelectrodes were characterized with cyclic voltammetry, scanning electron microscope (SEM), and optical interferometry. The surface area and roughness factor of each microelectrode were determined and reproducible values were obtained for all the microelectrodes on the array. In this work, the microelectrodes were modified with membranes for the detection of pH and nitrate ions to prove the reliability of the fabricated sensor array platform adapted to an endoscope.

Keywords: Chemical sensors, Cyclic voltammetry, Electrochemistry, Endoscopy, Fabrication, Implants (surgical), Microelectrodes, Needles, Nitrates, Scanning electron microscopy, Biomedicine, Fabricated sensors, Fabrication equipment, Implantable devices, Implantable sensors, Optical interferometry, Planar electrode, Roughness factor, Ion selective electrodes

Hoyo, J., Guaus, E., Torrent-Burgués, J., Sanz, F., (2012). Electrochemical behaviour of mixed LB films of ubiquinone - DPPC Journal of Electroanalytical Chemistry 669, 6-13

The structure and the electrochemical behaviour of Langmuir and Langmuir-Blodgett (LB) films of the biological ubiquinone-10 (UQ) and a mixture of dipalmytoilphosphatidylcholine (DPPC) and UQ at the molar ratios DPPC:UQ 5:1 and 10:1 have been investigated. The surface pressure-area isotherms of the Langmuir films and the AFM images of the LB films show the formation of a monolayer in the DPPC:UQ mixture till a certain surface pressure is attained, and then at higher surface pressures the UQ is progressively expelled. The cyclic voltammograms of DPPC:UQ LB films formed on indium tin oxide, ITO, at different surface pressures show one reduction and one oxidation peak at low surface pressures, but two or even more reduction and oxidations peaks at medium and high surface pressures. The electrochemical behaviour is correlated with the film structure.

Keywords: Cyclic voltammetry, Electron transfer, Langmuir-Blodgett, Lipid monolayer, Modified ITO electrode, Ubiquinone

Guaus, E., Torrent-Burgues, J., Zine, N., Errachid, A., (2009). Glassy carbon electrode modified with a langmuir-blodgett film of a thiomacrocyclic ionophore for Cu(II) recognition Sensor Letters 6th Maghreb-Europe Meeting on Materials and Their Applications for Devices and Physical, Chemical and Biological Sensors , AMER SCIENTIFIC PUBLISHERS (Rabat, Morocco) 7, (5), 1006-1011

Nanometric films of a thiomacrocyclic ionophore, 4-phenyl-4-sulfide-11(1- oxodecyl)-1,7-dithia-11-aza-4-phosphacyclotetradecane (ThM), have been deposited on the surface of a Glassy Carbon Electrode (GCE) by the Langmuir-Blodgett (LB) technique. The films have been characterised by using AFM. The influence of these modified electrodes (GCE-ThM) on the reduction of Cu(II) ions has been investigated by using Cyclic Voltammetry (CV) and Electrochemical Impedance Spectroscopy (EIS), and its sensor response has been checked. The CV and EIS responses of LB films on GCE indicate that these ThM films are sensitive to Cu(II) ions. The analysis by EIS of the interference of some other cations, as Mg(II) and Co(II), shows that LB films of ThM can be used for specific Cu(II) sensing applications.

Keywords: Cu(II) sensor, Cyclic voltammetry, Electrochemical impedance spectroscopy, Langmuir-blodgett films

Guaus, E., Errachid, A., Torrent-Burgues, J., (2008). Voltammetric response of a glassy carbon electrode modified by a Langmuir-Blodgett film of a thiomacrocyclic compound Journal of Electroanalytical Chemistry 614, (1-2), 73-82

A Langmuir-Blodgett (LB) film of a thiomacrocyclic (ThM) compound was deposited on the surface of a glassy carbon electrode (GCE) sheet, from a subphase containing Cu(II) ions. The study of the voltammetric response of this modified GCE when the ThM was bonded to Cu2+, showed that the films had the behaviour of confined species of an electrode surface, and that the current density of the voltammograms increased with the number of LB layers deposited. On the other hand, a LB film of the ThM compound was deposited on the surface of a GCE sheet from a subphase of pure water. When the voltammetric response of the GCE-ThM electrode was studied in a Cu2+-SO42- solution, it was found that a membrane model applies to describe the effect of the LB film on the GCE surface.

Keywords: Modified electrodes, Langmuir-Blodgett films, Cyclic voltammetry, Permeation at LB films, Membrane model of a thin film