Surface molecularly imprinted electrochemical sensor for phenol based on SiO2 nanoparticles

Abstract

A novel surface molecularly imprinted electrochemical sensor (MIECS) for the recognition and detection of phenol was constructed by dispersing a molecularly imprinted polymer (MIP) film on a multi-walled carbon nanotube (MWNTs) modified glass carbon electrode (GCE). An adsorption equilibrium of phenol to polyethyleneimine (PEI, grafted to SiO₂ nanoparticles) was achieved before molecular imprinting was carried out towards PEI by using phenol as a template and ethylene glycol diglycidyl ether (EGDE) as a cross-linker. The MIP was fabricated after the removal of phenol and the etching of SiO₂ nanoparticles. The obtained MIP and MIECS were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The sensor exhibited a remarkable enhancement of current response since the charge transfer process was facilitated by the etching of SiO₂ nanoparticles and the modification of GCE with MWNTs–COOH. The sensor showed specific recognition ability to phenol rather than other phenolic compounds with an excellent repeatability since the recognition sites were distributed on the surface of the polymer. The linear range of the calibration curve was 1 × 10⁻⁸ to 1.8 × 10⁻⁶ M with a detection limit of 4.2 × 10⁻⁹ M (S/N = 3) when potassium ferricyanide was used as the electrochemically active probe, superior to the other electrochemical sensors reported in the literature. The fabricated sensor exhibited a good performance in the determination of phenol in real samples as well.