Nanostructured electropolymerized poly(methylene blue) films from deep eutectic solvents. Optimization and characterization

Electropolymerization in deep eutectic solvents (DES) as a new class of green solvents, was employed to prepare poly(methylene blue) (PMB) polymers with different nanostructured morphologies. PMB films were synthesized on glassy carbon electrodes by potential cycling from a mixture of 90% ethaline (choline chloride: ethylene glycol) and 10% aqueous solution with different ionic composition, i.e. Na+, SO42, CIO4, NO3, Cl. The scan rate during polymerization was the key parameter in controlling film structure, confirmed by scanning electron microscopy. Electrochemical characterization of the polymers demonstrated differences in the electrochemical voltammetric and impedance properties of all synthesized PMB films. The PMB film obtained at 150 mV s(-)1 polymerisation scan rate with stirring, formed nanostructured ordered and granular films, was shown to have superior electrochemical properties. Electrochemical quartz crystal microbalance gravimetry was used to quantify the amount of deposited film and probe the polymerization mechanism. PMB film modified electrodes obtained in optimized DES media at different scan rates were tested for ascorbate sensing, in order to establish the most suitable PMBDES film for (bio)sensing applications. (C) 2017 Elsevier Ltd. All rights reserved.