Browsing by Author "Ramirez, A. M. R."

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    Capacitors Based on Polypyrrole Nanowire Electrodeposits
    (2022) Ramirez, A. M. R.; del Valle, M. A.; Ortega, E.; Diaz, F. R.; Gacitua, M. A.
    The electrochemical polymerization of polypyrrole nanowires is carried out using potentiodynamic and galvanostatic methods in order to enhance the performance of the modified electrodes as capacitor devices. The electrochemical, spectroscopic, and morphological properties are determined through cyclic voltammetry, Raman spectroscopy and scanning electron microscopy, respectively, corroborating the presence of PPy-nw in dimensions of 30 nm in diameter. Characterization as a capacitor revealed that the nanowire structure enhances key parameters such as specific capacitance with 60 times greater value than bulk polymer modification, in addition to a significant increase in stability. In this way, it is verified that electrodes modified with polypyrrole nanowires obtained in situ by electrochemical methods constitute an excellent candidate for the development of capacitors.
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    EFFECT OF THE MONOMERS RATIO IN THE ELECTROSYNTHESIS OF POLY(ANILINE-CO-O-METHOXYANILINE) ON STEEL CORROSION PROTECTION
    (2020) Del Valle, M. A.; Mieres, E.; Motheo, A.; Ramirez, A. M. R.
    In this work, the synthesis of poly(aniline-co-o-methoxyaniline) was carried out on AISI 304 steel, by voltammetric or potentiostatic method. Electropolymerization was achieved from different ratios of 0.4 mol.L-1 aniline/o-methoxyaniline monomers in 1.0 mol.L-1 H2SO4. Homo- and copolymers were characterized by cyclic voltammetry, infrared spectroscopy, and scanning electron microscopy. Furthermore, the electrodeposits were studied with a view to their use as corrosion protectors, for which their polarization curve was measured in NaCl 3% and, after 168 h, the surface of the steel was also evaluated by optical microscopy. It was observed that the reactivity that the o-methoxy group gives to the aniline ring reduces the protection against corrosion due to the excessive inclusion of N-phenyl-1,4-benzo quinonedi-imine oligomers and/or with an oxazine structure. On the other hand, the optical images confirm the surface damage of the steel, correlating with SEM images that show morphological changes associated with the progress of synthesis and the o-methoxy group. Nevertheless, under optimal conditions, poly(aniline-co-o-methoxyaniline) modifies the corrosion potential of AISI 304 steel, displacing it by 0.283 V. Furthermore, the presence of small pits and the absence of surface oxide was observed, indicating a significant delay in the oxidation of AISI-304 steel.
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    Electrochemical in situ synthesis of polypyrrole nanowires
    (2019) Ramirez, A. M. R.; Gacitua, M. A.; Ortega, E.; Diaz, F. R.; del Valle, M. A.
    Modification with polypyrrole nanowires, PPy-nw, is accomplished directly upon the working electrode by electrochemical polymerization methods using mesoporous silica as a template. The silica template is prepared by a potentiostatic method, generating a homogeneous film over a previously deposited thin layer of PPy, so that PPy-nw grows within the nanochannels of the mesoporous silica and adheres firmly to the surface. Subsequently the template is removed to obtain intact Pt vertical bar PPy-nw with stable and reproducible electrochemical properties, and with an enhanced (about 360 times higher charge capacity) response after charge-discharge experiments compared to equivalent electrodes modified with polymer deposits in the bulk (PPy) form. SEM reveals the brush-type conformation of PPy-nw (30 nm in diameter). Thus, a cheap, simple, highly repeatable method is used in situ to prepare electrodes modified with nano-structured polymers, using electrochemical techniques alone. This could have a great impact on a wide range of applications of conducting polymers.
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    UV-VIS SPECTROELECTROCHEMICAL IN SITU STUDY DURING THE ELECTROSYNTHESIS OF COPOLYMERS
    (2019) del Valle, M. A.; Motheo, A.; Ramirez, A. M. R.
    In this work, the synthesis of poly(aniline-co-o-methoxyaniline) is performed using purely electrochemical techniques, coupled to UV-vis spectroscopy in situ, in 3D. The electrocopolymerization is carried out on ITO electrodes, in various monomer ratios aniline/o-methoxyaniline varying between 0.1 to 0.4 mol L-1 in H2SO4 1.0 mol L-1 The homo- and copolymers were characterized by cyclic voltammetry, in situ UV-Visible, and scanning electron microscopy. The results show the important information provided by UV-Visible spectroscopy coupled with electrochemical techniques. Thus, it is observed that the reactivity that gives the o-methoxy group in the aniline ring, damages the conductivity of the polymer, due to the occlusion of oligomers of N-phenyl-1,4-benzoquinonediimine and/or with the structure of oxazine. On the other hand, the SEM images show morphological changes associated with the progress of the synthesis, which can be related with the less conductivity produced by o-methoxy, despite the greater reactivity.