An electrochemically exfoliated graphene/poly(3,4-ethylenedioxythiophene) nanocomposite-based electrochemical sensor for the detection of nicotine

Abstract

A novel, simple and ‘green’ electrochemical exfoliation method was used to prepare a graphene (GR) dispersion. The as-obtained GR was characterized using HR-TEM, which confirmed the exfoliation of a few layers of graphene from graphite sheets. Furthermore, the GR film was coated on a glassy carbon electrode (GCE) surface via drop-casting. Then, electro-polymerization was carried out using the GR-modified electrode in acetonitrile solution (ACN) containing 10 μM 3,4-ethylenedioxythiophene (EDOT) and 100 mM lithium perchlorate (LiClO₄). The electro-polymerized PEDOT (poly(3,4-ethylenedioxythiophene)) on the GR film-modified electrode was analyzed using FE-SEM and Raman spectroscopy, which confirmed the successful incorporation of PEDOT on the GR surface. The electrochemical characterization of PEDOT/GR/GCE was carried out by electrochemical impedance spectroscopy (EIS) in 0.1 M KCl containing 5 mM [Fe(CN)₆]^3−/4−. The electrochemical measurements revealed that our proposed PEDOT/GR film exhibited a high active surface area, redox currents and high charge transfer rate (K_s). Under optimized conditions, PEDOT/GR/GCE showed a higher oxidation peak current for nicotine at +0.91 V (vs. Ag/AgCl) in 0.1 M phosphate buffer solution (PBS; pH 7). Furthermore, PEDOT/GR/GCE responded linearly for nicotine detection from 0.5 to 1000 μM with a limit of detection at 47 nM. The selectivity and sensitivity of the electrochemical sensor (PEDOT/GR/GCE) were determined in the presence of important interfering molecules. In addition, the stability and reproducibility of the PEDOT/GR/GCE sensor were tested. Finally, the PEDOT/GR-based sensor was successfully applied to detect nicotine in tobacco samples with high accuracy.