Browsing by Author "Martinez-Rojas, Francisco"

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    Carbon dioxide electrochemical reduction by copper nanoparticles/ionic liquid-based catalytic inks
    (2024) Gazzano, Valeria; Mardones-Herrera, Elias; Saez-Pizarro, Natalia; Armijo, Francisco; Martinez-Rojas, Francisco; Ruiz-Leon, Domingo; Honores, Jessica; Isaacs, Mauricio
    The development of copper nanoparticle (CuNP)-based catalysts for the electrochemical reduction of carbon dioxide (ECO2-R) offers a promising approach to enhance its transformation into other industrially significant compounds. This study reports ECO2-R at -1.3 V vs RHE using CuNPs and catalytic inks composed of CuNPs and ionic liquids (ILs), observing significant differences in the selectivity of each catalyst. Specifically, CuNPs alone show a preference for producing ethylene and aqueous products, such as formic acid, ethanol, and formaldehyde. In contrast, the addition of ILs to the catalytic system redirects selectivity toward gaseous products, with methane being the main product. These findings highlight the potential to optimize catalyst composition to tailor the selectivity of CO2 conversion processes. ILs modify the catalytic environment and influence reaction pathways, enabling the selection of specific products.
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    Electrochemical oxidation of chlorpromazine, characterisation of products by mass spectroscopy and determination in pharmaceutical samples
    (2023) Martinez-Rojas, Francisco; Espinosa-Bustos, Christian; Ramirez, Galo; Armijo, Francisco
    The electrochemical behaviour of chlorpromazine (CPZ) at different pH values was studied using a fluorinedoped tin oxide (FTO) electrode. Cyclic voltammetry (CV), square-wave voltammetry (SWV), electrochemical impedance spectroscopy (EIS), and constant-potential electrolysis were used to elucidate the electrooxidation mechanism of CPZ on the FTO electrode, whereas chronoamperometry was used to determine CPZ in pharmaceutical and water samples. In addition, using mass spectrometry (MS), it was determined that the main oxidation product was the metabolite chlorpromazine sulfoxide (CPZ-SO). When electrolysis was performed at 1.45 V and pH 2, two metabolites were detected by MS, and a competitive mechanism was proposed wherein CPZ-SO was obtained simultaneously. Linear analytical curves were obtained between 2 x 10-6 and 100 x 10-6 mol L-1, and the detection limit was determined to be 0.26 x 10-6 mol L-1. The developed electroanalytical method thereby presents an appropriate sensitivity and stability that renders it suitable for use in the quality control and routine quantification of pharmaceutical formulations and samples containing environmentally relevant concentrations.
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    Formation of a Conducting Polymer by Different Electrochemical Techniques and Their Effect on Obtaining an Immunosensor for Immunoglobulin G
    (2023) Martinez-Sade, Erika; Martinez-Rojas, Francisco; Ramos, Danilo; Aguirre, Maria Jesus; Armijo, Francisco
    In this work, a conducting polymer (CP) was obtained through three electrochemical procedures to study its effect on the development of an electrochemical immunosensor for the detection of immunoglobulin G (IgG-Ag) by square wave voltammetry (SWV). The glassy carbon electrode modified with poly indol-6-carboxylic acid (6-PICA) applied the cyclic voltammetry technique presented a more homogeneous size distribution of nanowires with greater adherence allowing the direct immobilization of the antibodies (IgG-Ab) to detect the biomarker IgG-Ag. Additionally, 6-PICA presents the most stable and reproducible electrochemical response used as an analytical signal for developing a label-free electrochemical immunosensor. The different steps in obtaining the electrochemical immunosensor were characterized by FESEM, FTIR, cyclic voltammetry, electrochemical impedance spectroscopy, and SWV. Optimal conditions to improve performance, stability, and reproducibility in the immunosensing platform were achieved. The prepared immunosensor has a linear detection range of 2.0-16.0 ng center dot mL(-1) with a low detection limit of 0.8 ng center dot mL(-1). The immunosensing platform performance depends on the orientation of the IgG-Ab, favoring the formation of the immuno-complex with an affinity constant (Ka) of 4.32 x 10(9) M-1, which has great potential to be used as point of care testing (POCT) device for the rapid detection of biomarkers.