Electrochemical Functionalization of N-Methyl-2-pyrrolidone-Exfoliated Graphene Nanosheets as Highly Sensitive Analytical Platform for Phenols

Graphene nanosheets (GS) were easily prepared from graphite via a one-step ultrasbnic exfoliation approach using N-thethyl-2-pyrrolidone (NMP), as the solvent Compared with the widely used graphene oxide obtained by multistep chemical oxidation, the NMP-exfoliated GS exhibited apparently better electrochemical activity toward the oxidation of a series of phenols like hydroquinone, catechol, 4-chlorophenol, and 4-nitrophenol. Interestingly, the electrochemical activity of GS toward these phenbls can be ftirdter enhanced by simply anodizing at 1.8 V for 2 min (denoted as EGS), reflected by the apparently enlarged oxidation peak currents in voltammograms and the obviously reduced charge transfer resistance in electrochemical impedance spectra (EIS). Characterizations by techniques like X-ray photoelectron spectra (XPS), Raman spectra, and atomic force microscopy (AFM) demonstrated that the introduction of new oxygen containing groups or edge plane defects and the enhanced surface roughness were responsible for the enhanced activity of EGS. Thereafter, a simple electrochemical method for the highly sensitive detection of phenols was established and the detection limits were 0.012 mu M, 0.015 mu M, 0.01 mu M, and 0.04 mu M for hydroquinone, catechol, 4-chlorophenol, and 4-nitrophenol, respectively. The facile synthesis of EGS, together with its high electrochemical activity, thus created a ritivel platform for developing highly sensitive electrochemical sensing systems.