In this work, the surface of a glassy carbon electrode (GCE) was modified with the polymer of 5-Amino-1-10 phenanthroline (5Aphen), Poly5Aphen, from a deep eutectic solvent (DES). The electrochemical response of the modified electrode (GCE/Poly5Aphen) was established regarding the oxidation of dopamine (DA) in the presence of ascorbic acid (AA) that is one of its major interferents. The results obtained by cyclic voltammetry (CV) showed that it is possible to polymerize 5Aphen on the surface of the GCE when using a DES. On the other hand, the results by CV and differential pulse voltammetry (DPV) showed that, unlike the bare GCE, when using the GCE/Poly5Aphen electrode it is possible to separate the electrochemical signal of the DA and AA as result of their simultaneous oxidation over the modified surface of the electrode.
This work presents the results obtained on the construction of a potentiometric ion-selective electrode based on a polypyrrole (PPy) selective membrane to quantify the benzoate ion in nonalcoholic beverages. The electrode modification with benzoate (Benz À1 ) ion doped-Ppy was carried out under an imposed potential, while the electrosynthesis optimization was undertaken using the modified Simplex method, such that the films sensitivity was maximized toward the benzoate ion. The maximum sensitivity recorded was À52.02 AE 1.55 mV/decade [Benz À1 ] using a graphite powder-araldite resin composite electrode. During the modified electrodes characterization it was found out that the response and drift were relatively short, namely 2 min and 0.4 mV min À1 respectively, within the 7 to 9 pH range, exhibiting a detection limit of 7 10 À4 mol L À1 and a quantification range of 3 10 À3 at 10 À1 mol L À1 . Selectivity coefficients were evaluated with the Matched Potential Method obtaining in all cases values much less than 1. The benzoate concentration in commercially available juices and sweetened beverages was evaluated comparing the results obtained with the proposed ion-selective electrode and those of HPLC, the usually accepted technique. A statistical analysis of the results led to the conclusion that there exists no meaningful difference between the results obtained with both techniques, which shows the usefulness of the ion-selective electrode to proceed with the quantification in real samples.
The objective of this research is the production of an epoxy coating blended with organic–inorganic hybrid nanocomposite applied over mild steel, as a self-healing corrosion protection of defects. A series of conducting polyaniline (PANI)–SBA15/Fluconazole nanocomposites materials are being prepared by an in situ chemical oxidative method of aniline monomers in the presence of SBA15/fluconazole complex nanorods which were synthesized previously with camphor-sulfonic acid (CSA) and ammonium peroxydisulfate (APS) as surfactant and initiator, respectively. A commercial epoxy coating was applied over samples afterwards. The synthesized materials were characterized by X-ray diffraction pattern (XRD), Fourier transform infrared (FTIR), scanning electron microscopy (SEM). To determine the best inhibitor concentration, the anti-corrosion behavior of the Fluconazole was studied in a ammonium sulfide-sodium chloride pH 7 solution, at a temperature of 25 ͦ C using electro-chemical techniques including electrochemical impedance spectroscopy (EIS) and polarization potentiodynamic. The electrochemical results show that this inhibitor has an effect on anodic region forming a passivation layer, and the best result was achieved with 150 ppm of Fluconazole. The next step was to prepare the SBA15/Fluconazole nanorods, and finally the PANI-SBA15/Fluconazole composite, and evaluate the self-healing effect over mild steel. It was found that the presence of SBA15/Fluconazole nanorods dispersed in the PANI matrix can significantly improve the corrosion protection and barrier effect performance of the epoxy coating due to the flaky shaped structure of the PANI–SBA15/Fluconazole nanocomposites, evaluated electrochemically.
In this work, the mechanism of nucleation and growth of gold was studied on the surface of a glassy carbon electrode (GCE) modified with poly-5-Amino-1-10 phenanthroline (Poly5Aphen), from Au (III) ions, dissolved in a deep eutectic solvent (DES). For which, electrochemical techniques such as cyclic voltammetry (VC) and chronoamperometry (CA) were used. The analysis of the results of the potentiostatic electrochemical tests showed that the Au nucleation and growth mechanism on the GCE/Poly5Aphen electrode fits a theoretical model of 3D nucleation limited by diffusion and by the reduction of residual water present in the electrode (1). In addition, the potentiostatic current density transients recorded during gold electrodeposition on the modified electrode (GCE/Poly5Aphen), when presented in their dimensionless form I2/ I2 m vs t /tm and compared with the theoretical models described by Scharifker and Hills (2), the experimental data did not fit the progressive or instantaneous nucleation models, presenting particularly large deviations for >1.4.
Palladium-based bimetallic electrocatalysts supported on graphene oxide were synthesized by the impregnation method, for evaluation of the formic acid oxidation reaction (FAOR) in an acid medium. The electrocatalysts were evaluated physicochemically by means of X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques, to know the chemical composition, distribution on the support and crystal size. The evaluation of the electrocatalytic activity was carried out using the electrochemical techniques of cyclic voltammetry (CV) and chronoamperometry (CA) using the steady state current density (jss) electrochemical parameter.
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