Nanocomposites based on carbon nanotubes and redox-active polymers synthesized in a deep eutectic solvent as a new electrochemical sensing platform

The redox polymer poly(methylene blue) was synthesized by electropolymerization in ethaline deep eutectic solvent (PMBDES), and employed in a new nanostructured composite together with carbon nanotubes (CNT). The polymer was formed either before or after CNT deposition on glassy carbon electrodes (GCE) to obtain GCE/PMBDES/CNT and GCE/CNT/PMBDES modified electrodes, respectively. The morphology of the hybrid films was investigated by scanning electron microscopy, and their electrochemical performance by cyclic voltammetry and electrochemical impedance spectroscopy. The composite with the highest faradaic response and electronic conductivity was identified and applied as a platform for the determination of ascorbic acid by fixed potential amperometry at +0.2 V vs. Ag/AgCl, and acetaminophen by square wave voltammetry and differential pulse voltammetry at +0.67 V vs. Ag/AgCl. The limits of detection of the best sensor configurations are 1.7 μM for AA, and 1.6 μM for APAP, and respective electrochemical sensitivities are 2.2 μA cm-2 μM−1 and 68.7 μA cm-2μ​M-1. The applicability of the electrochemical sensors was demonstrated by the successful quantification of both these key analytes in complex pharmaceutical formulations.