Electrochemical polymerization of aniline over tetracyanoquinodimethane encapsulated ormosil matrix: application in the electrocatalytic oxidation of ascorbic acid and acetylthiocholine

Abstract

Organically modified sol–gel glass (ormosil) matrix is utilized as a template for the electrochemical polymerization of aniline. The ormosil matrix is further modulated by encapsulation of: (a) tetracyanoquinodimethane (TCNQ), and (b) tetracyanoquinodimethane together with palladium (Pd). The presence of tetracyanoquinodimethane within ormosil matrix considerably influences the polymerization process of aniline and the same is significantly enhanced as compared to that of control. The presence of palladium within ormosil network further influence the polymerization process as compared to that of TCNQ only. The polyaniline obtained as PAni–TCNQ and PAni–TCNQ–Pd composites has been utilized for fabricating the modified electrodes. These modified electrodes are used to study the electrochemical sensing of ascorbic acid and acetylthiocholine. The results based on cyclic voltammetry, differential pulse voltammetry and amperometry justify that the electrode material exhibits excellent electrocatalytic activity for the oxidation of ascorbic acid and acetylthiocholine with major findings as compared to the control: (1) a negative shift to the order of ∼340 mV vs.Ag/AgCl in the anodic overpotential for the electro-oxidation of ascorbic acid, (2) a significant increase in the anodic peak current for the oxidation of ascorbic acid, (3) an increase in the sensitivity of ascorbic acid analysis to the order of 7-fold for the modified electrodes, (4) acetylthiocholine undergoes direct oxidation with considerable increase in both anodic and cathodic peak currents and (5) an increase in the sensitivity of acetylthiocholine analysis to the order of 5-fold for the modified electrodes.