Amperometric ethanol biosensor based on carbon nanotubes dispersed in sol-gel-derived titania-Nafion composite film

Composite solution of sol-gel-derived titania and perfluorosulfonated ionomer (Nafion) was used as a solubilizing agent for multiwalled carbon nanotubes (CNT) as well as an encapsulation matrix for alcohol dehydrogenase (ADH) for the fabrication of a highly sensitive and stable amperometric ethanol biosensor. ADH was immobilized within a thin film of CNT-titania-Nafion composite film coated on a glassy carbon electrode. Because of the mesoporous nature of the CNT-titania-Nafion composite film, the present biosensor exhibited remarkably fast response time within 2 s. The presence of CNT in the composite film increases not only the sensitivity of the ethanol biosensor but also the long-term stability of the biosensor. The present biosensor responds linearly to ethanol in the wide concentration ranges from 1.0 × 10^-5 M to 3.0 × 10^-3 M with the sensitivity of 51.6 mA M ^-1cm^-2. The present biosensor showed good long-term stability with 75% of its activity retained after 4 weeks of storage in 50 mM phosphate buffer at pH 7.0.