Browsing by Author "Ramirez, Galo"

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    Electrodetermination of Gallic Acid Using Multi-walled Carbon Nanotube Paste Electrodes and N-Octylpyridinium Hexafluorophosphate
    (WILEY-V C H VERLAG GMBH, 2022) Gidi, Leyla; Honores, Jessica; Ibarra, Jose; Jesus Aguirre, Maria; Arce, Roxana; Ramirez, Galo
    In this work, the determination of gallic acid was performed using surface-renewable carbon paste electrodes fabricated with multi-walled carbon nanotubes (MWCNT) and a mixture of N-octylpyridinium hexafluorophosphate (OPyPF6) ionic liquid with mineral oil (MO) as binder. This system shows remarkable amperometric sensor characteristics and promotes a better electronic transfer. An electroanalytical study of gallic acid shows a linear range from 4.98 +/- 0.25 to 74.1 +/- 2.2 mu mol L-1, with R-2=0.9958 and an experiment a limit of detection of 2.70 +/- 0.08 mu mol L-1 (S/N=3), and a sensitivity of 0.029 mu A mu mol(-1) L.
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    Leyla Gidi, Camila Canales, Maria J. Aguirre, Francisco Armijo, and Galo Ramirez, Four-Electron Reduction of Oxygen Electrocatalyzed by a Mixture of Porphyrin Complexes onto Glassy Carbon Electrode (vol 13, pg 1666, 2018)
    (ESG, 2018) Gidi, Leyla; Canales, Camila; Aguirre, Maria J.; Armijo, Francisco; Ramirez, Galo
    © 2018 The Authors.The exact received date of the paper is 24 October 2017 year.
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    Nitrite electro-oxidation mediated by Co(II)-[tetra(4-aminophenyl)porphyrin]-modified electrodes: behavior as an amperometric sensor
    (TAYLOR & FRANCIS LTD, 2010) Rios, Roxana; Marin, America; Ramirez, Galo
    Electro-oxidation of nitrite mediated by Co(II)-[tetra(4-aminophenyl)porphyrin]-modified electrodes (4-CoTAPP) is presented in this article. Catalytic activity of electrodes modified with porphyrin polymeric films (poly-4-CoTAPP) and with multilayer of monomers (m-4-CoTAPP) for the oxidation of nitrite was compared. The number of cycles for the electrosynthesis of poly-4-CoTAPP determines the activity of the electrode toward nitrite oxidation because the system loses its catalytic activity as the number of polymerization cycles increases above 15. The effect of pH on activity is also reported. The response for the nitrite oxidation of electrodes modified with 4-CoTAPP and with metal-free ligand, that is, tetra(4-aminophenyl)porphyrin, either as multilayer of monomers or as polymer (m-4-H2TAPP and poly-4-H2TAPP, respectively), was compared. An increase of activity in the presence of the metal was found. Furthermore, when the device was tested as an amperometric sensor for different nitrite concentrations under the optimum working conditions, only poly-4-CoTAPP exhibited a linear response throughout the concentration range studied with a reasonably low limit of detection, while m-4-CoTAPP and poly-H2TAPP systems have no linear response throughout the range of concentration. Finally, the number of electrons involved and the Tafel slope for the reaction were estimated.
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    Study of the Hydrogen Evolution Reaction Using Ionic Liquid/Cobalt Porphyrin Systems as Electro and Photoelectrocatalysts
    (MDPI, 2020) Gidi, Leyla; Honores, Jessica; Ibarra, Jose; Arce, Roxana; Aguirre, M. J.; Ramirez, Galo
    In this work, the design and manufacture of graphite paste (Gr) electrodes is carried out, including N-octylpyridinium hexafluorophosphate (OPyPF6) ionic liquid (IL) as binder and modification with Co-octaethylporphyrin (Co), in order to study the hydrogen evolution reaction (HER) in the absence and presence of light. The system is characterized by XRD and FESEM-EDX (Field Emission Scanning Electron Microscopy with Energy Dispersive X-Ray Spectroscopy), confirming the presence of all the components of the system in the electrode surface. The studies carried out in this investigation confirm that a photoelectrocatalytic system towards HER is obtained. The system is stable, efficient and easy to prepare. Through cyclic voltammetry and electrochemical impedance spectroscopy, was determined that these electrodes improve their electrochemical and electrical properties upon the addition of OPyPF6. These effects improve even more when the systems are modified with Co porphyrin. It is also observed that when the systems are irradiated at 395 nm, the redox process is favored in energy terms, as well as in its electrical properties. Through gas chromatography, it was determined that the graphite paste electrode in the presence of ionic liquid and porphyrin (Gr/IL/Co) presents a high turnover number (TON) value (6342 and 6827 in presence of light) in comparison to similar systems reported.