Electropolymerization of phenol and aniline derivatives: Synthesis, characterization and application as electrochemical transducers

Abstract

In this work we synthesized, characterized (electrochemically, morphologically and structurally) and proposed an electropolymerization mechanism to obtain polymer films derived from 4-aminobenzoic acid (4-ABA), 4-aminobenzamide (4-ABZ), 4-hydroxybenzoic acid (4-HBA) and 4-hydroxybenzamide (4-HBZ) to be used as electrochemical transducers applied to the initial development of an immunosensor for dengue. The electropolymerization of these monomers over graphite electrodes (GE) in 0.5M sulfuric acid solution was obtained using cyclic voltammetry (CV), and applying 100 potential cycles at 50mV/s. The characterization of the polymeric films was performed by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), cyclic voltammetry, and electrochemical impedance spectroscopy (EIS). All the polymer films obtained showed adsorption on the surface of the GE, and showed electrochemical activity in the potential region of 0.3 to 0.8V. SEM images proved the modification of the graphite electrodes surfaces by the polymeric films with specific morphological characteristics for each polymeric film. FTIR and NMR analysis show the presence of C–O–C bond for the poly(4-HBA) and poly(4-HBZ) suggesting that the polymerization begins through the phenolic hydroxyl group. Similarly, for the poly(ABA) and poly(ABZ) the polymerization occur through the amino group attached to the ring, resulting in C–N–C bond. In all cases, the carboxyl and amide groups were preserved in the polymers. The electropolymerization mechanism and chemical structures of the polymers were proposed, including the oxidized and reduced form of the compounds. Preliminary studies for the rNS1 immobilization performed by physical adsorption were evaluated through the four studied transducers, including analysis of the serum samples human containing positive and negative antibodies to dengue. The poly(4-HBA) and poly(4-ABA) presented greater sensitivity in the recognition of positive targets of the disease with an increase approximate of 65% in the obtained signal with respect to the antigen for both cases.