Development of imprinted polyneutral red/electrochemically reduced graphene oxide composite for ultra-trace sensing of 6-thioguanine

The present work describes a novel method for the fabrication of a pencil graphite electrode modified with polyneutral red/electrochemically reduced graphene oxide (ERGO) composite, for sensing 6-thioguanine (anticancerus drug), in biological and pharmaceutical samples. Herein, the neutral red monomer was electro-polymerized in the presence of 6-thioguanine (template) at −0.9 V directly over ERGO nano sheets coated electrode. After the template extraction, an imprinted polymer coating on ERGO was obtained. The monomer-template (1:2) stoichiometry was optimized through density functional theory at the B3LYP/6-31 + G (d, p) level. In this work, graphene oxide (GO) sheets actually assumed exfoliated anionic texture which facilitated electro-statically deposition of cationic molecules of neutral red at neutral pH. These molecules were subsequently electro-polymerized accompanied with simultaneous electro-reduction of exfoliated GO. This resulted in highly electro-conductive polyneutral red coated ERGO nano sheets alongwith probable intercalation of the polymer into the space between the exfoliated two proximate ERGO layers. A perfect linearity in the current-concentration profile was observed for the analyte concentration in the range 0.124-78.0 ng mL−1, with the detection limit 0.02 ng mL−1 (S/N = 3), in aqueous medium. The proposed sensor assured a reliable analysis of ultra-trace 6-thioguanine in real samples.