A thionine functionalized multiwalled carbon nanotube modified electrode for the determination of hydrogen peroxide

An amperometric sensor for hydrogen peroxide was developed using multiwalled carbon nanotubes (MWCNTs) covalently immobilized with thionine (TH) via a carbodiimide reaction. The thionine functionalized MWCNTs were then abrasively transferred onto a paraffin impregnated graphite electrode followed by a coating of a thin film of nafion (Nf). The immobilization of thionine with MWCNTs was characterized by UV–visible absorption spectroscopy, diffuse reflectance UV–visible spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, thermogravimetry, electrochemical impedance spectroscopy and cyclic voltammetry. The cyclic voltammetric response of thionine grafted onto CNTs indicated that it promotes the low potential, sensitive and stable determination of H2O2. The modified electrode showed an inherent stability over a wide pH range, fast response time, high sensitivity, low detection limit and remarkable decrease of over potential for the reduction of hydrogen peroxide that decreases interference in analysis. This TH/MWCNT/Nf modified electrode can be used as an amperometric detector for monitoring oxidase based biosensors in chromatography and in flow injection analysis.