Interfacial adsorption and antifouling mechanisms of bisphenol A at a CTAB-modified carbon paste electrode: insights from electrochemistry, adsorption modeling, and molecular simulation.

Surfactants are widely employed to engineer electrode interfaces with improved electrochemical properties, such as enhanced analyte preconcentration through adsorption, faster electron-transfer kinetics, and increased selectivity. Moreover, surfactant layers can suppress electrode fouling during the oxidation of analytes. Nevertheless, the mechanistic relationship between analyte adsorption and the antifouling behavior imparted by surfactants remains largely unexplored. In this work, a carbon paste electrode modified with cetyltrimethylammonium bromide (CTAB/CPE) was selected as a simple model system for the electrochemical detection of BPA, with the aim of minimizing excessive intermolecular interactions at the electrode interface and facilitating the investigation of the adsorption mechanism and antifouling behavior. Our study was investigated using cyclic voltammetry, supported by adsorption modeling and molecular simulations. The results revealed that CTAB significantly improves electrode performance by reducing surface fouling, improving current response, and enhancing sensitivity and reproducibility. The electrochemical oxidation process was found to involve an adsorption-controlled mechanism. Adsorption studies showed that the experimental data were best described by the Freundlich isotherm, indicating a heterogeneous surface with adsorption sites of different affinities toward BPA, while the Frumkin model suggested negligible lateral interactions between adsorbed BPA molecules. In addition, thermodynamic analysis revealed that the adsorption process is favorable and predominantly physical in nature, driven by ion-dipole and π-cation interactions. Density Functional Theory (DFT), Topological Quantum Theory of Atoms in Molecules (QTAIM), and The Noncovalent Interaction (NCI) analyses further confirmed favorable interfacial charge-transfer properties and the predominance of physisorption at the CTAB/CPE interface. Overall, BPA adsorption on CTAB/CPE occurs through weak intermolecular interactions with negligible lateral interactions which may suppress the polymerization of BPA oxidation products, thus improving the anti-fouling performance of the CTAB/CPE electrode.