A highly sensitive and selective glucose biosensor has been developed based on immobilization of glucose oxidase within mesoporous carbon nanotube -titania -Nafion composite film coated on a platinized glassy carbon electrode. Synergistic electrocatalytic activity of carbon nanotubes and electrodeposited platinum nanoparticles on electrode surface resulted in an efficient reduction of hydrogen peroxide, allowing the sensitive and selective quantitation of glucose by the direct reduction of enzymatically-liberated hydrogen peroxide at À 0.1 V versus Ag/AgCl (3 M NaCl) without a mediator. The present biosensor responded linearly to glucose in the wide concentration range from 5.0 Â 10 À5 to 5.0 Â 10 À3 M with a good sensitivity of 154 mA M À1 cm À2. Due to the mesoporous nature of CNT -titaniaNafion composite film, the present biosensor exhibited very fast response time within 2 s. In addition, the present biosensor did not show any interference from large excess of ascorbic acid and uric acid.

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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 Â 10 À5 M to 3.0 Â 10 À3 M with the sensitivity of 51.6 mA M À1 cm À2. 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.

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A simple amperometric detection (AD) method based on mesoporous platinum (Pt) electrodes has been developed for the determination of sugars (glucose, fructose, and sucrose) with high-performance anion-exchange chromatography (HPAEC). The amperometric detection is based on the direct oxidation of sugars on mesoporous Pt films formed on a gold electrode. The mesoporous Pt electrode (roughness factor of 243) sensitively responded to glucose, fructose, and sucrose in 80 mM sodium hydroxide solution as an alkaline mobile-phase for HPAEC. Under the optimum conditions, the limits of detection (S/N = 3) in these sugars were 0.24, 0.29, and 1.8 mM, for glucose, fructose, and sucrose, respectively. The reproducibility (relative standard deviation) of the measurements was less than 3.5%. The present method was applied to the determination of sugars in apple juice. The recoveries for all sugars ranged from 97 to 99%.