Probing the surface of oxidized carbon nanotubes by selective interaction with target molecules

Screen printed carbon electrodes (SPCE) were modified with pristine and oxidized carbon nanotubes (CNTprist and CNTox, respectively). The extent of CNT oxidation evaluated by TGA increasedwith the time of reflux in nitric acid. The CNTox surface coverage by quinoid/phenolic functional groupswas quantified by their voltammetric response at low redox potentials. Cyclic voltammetry was performed with SPCE-CNTox on solutions of hydroquinone, dopamine and ferricyanide used as model compounds. The sensitivity of reduced/oxidized forms of these molecules to the oxygen-containing functional groups of the CNTox was evaluated by the current intensity. Compoundswith phenol/amine groups showa large increase of the current intensity with increasing CNT oxidation, while for carbonyl containing compounds only a negligible effect was perceived. Molecules that can hydrogen bond to the CNT functional groups interact better with the electrode surface, and this is supported by theoretical calculations. This showcases the use of CNTox modified SPCE for selective sensing.PEst-C/QUI/UI0686/2013 (Research Centre CQ/UM), project UID/CEC/00319/2013 (Centro ALGORITMI), and project PEst-C/CTM/LA0025/2013 (IPC/I3N