Water-soluble single-walled carbon nanotubes films: Preparation, characterization and applications as electrochemical sensing films

Water-soluble single-walled carbon nanotubes (SWNTs) were prepared via noncovalent functionalization by Congo red through a physical grinding treatment. Based on the unique property of strong rebundling when dried, water-soluble SWNTs were firmly immobilized on the surface of a glassy carbon electrode by a simple casting method. The prepared films were characterized by scanning electron microscopy (SEM), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results showed that water-soluble SWNTs formed uniform films with porous network structures of nanosizes on the electrode surface, which were stable in neutral and acidic solutions but were unstable in basic media. In addition, the structural properties and the negative charge density of these films can be conveniently controlled by choosing proper solvents during the washing procedure, providing a simple approach for adjusting their properties to specific applications. For instance, the films prepared from water-soluble SWNTs by N,N′-dimethyl formamide (DMF) washing (SWNTs–CRDMF) had looser structures and lower negative charge density than those by water washing (SWNTs–CRwater), which allowed the entry and the succedent electrochemical reactions of both positively and negatively charged species inside the films. The potential applications of these films in electroanalytical chemistry were examined. The enhanced response of dopamine (DA) and the separation of DA oxidation potential from those of uric acid (UA) and ascorbic acid (AA) at these films demonstrated that the water-soluble SWNTs were the ideal materials for constructing SWNTs-based electrochemical sensing films.