Role of carbonaceous fragments on the functionalization and electrochemistry of carbon materials

Abstract

Carbonaceous fragments (CF) formed by acid treatment of carbon materials have important properties that are not completely understood. In this work, CF were produced by oxidation of CNT by using mineral acid followed by treatment with NaOH. The role of CF on CNT voltammetric properties was studied by using different materials: oxidized CNT (a-CNT), a-CNT refluxed in NaOH and neutralized with HCl (b-CNT), pristine CNT exposed to a CF suspension (c-CNT), and b-CNT exposed to a CF suspension (r-CNT). The extension of functionalization of these materials was evaluated by thermogravimetric analysis (TGA). The spectroscopic characterization (UV/Vis, fluorescence, FTIR, Raman and NMR) of CF indicates the presence of graphene-type conjugated aromatic rings with highly oxidized moieties. In this work we demonstrate that CF are responsible for the ameliorated voltammetric properties of oxidized CNT. Adsorption of CF on oxidized and non-oxidized CNT showed that CF provide active sites for hydroquinone (HQ) adsorption, enhancing current responses. The interaction of CF with carbon materials depended on both the surface oxidation degree and the surface roughness. Voltammograms from CF adsorbed on oxidized CNT indicate the presence of labile supramolecular structures with a voltammetric response typical of quinoid units. Carbon materials functionalized with CF displayed lower peak potentials and higher currents (30 to 180%) than the unmodified electrodes, demonstrating that CF is a promising material for sensors design.