Electrochemical behavior and analytical applications of electronically type-sorted carbon nanotube electrode

The electrochemical behavior and analytical applications of an electrode with electronically typesorted (metallic and semiconducting) single-walled carbon nanotubes (SWCNTs) were examined. The efect of the electronic type of SWCNTs on the electrochemical behavior of nicotinamide adenine dinucleotide (NADH) as a model agent was investigated. The electrode coniguration contained SWCNTs sandwiched between 3-5-nm-thick acetonitrile plasma-polymerized thin ilms. Cyclic voltammetry measurements demonstrated that the current due to the NADH oxidation of the electrode with semiconducting SWCNTs was much larger than that for electrodes with only metallic or unsorted SWCNTs. Electrochemical impedance spectroscopy measurements and atomic force microscopy observations suggested that the electrode with semiconducting SWCNTs formed a better electron transfer network than the electrodes with metallic or unsorted SWCNTs. Chronocoulometry measurements indicated that there was no distinct difference between the diffusion coefficients of NADH with the metallic and semiconducting SWCNT electrodes. Therefore, it was concluded that the semiconducting SWCNT electrode is more suitable than the metallic and unsorted SWCNT electrodes for electrochemical oxidation in terms of catalysis and electron transport. The semiconducting SWCNT electrode exhibited excellent performance for the sensing application of NADH detection with a signiicantly wide linear range of 59-5800 μM compared with that for conventional NADH sensors. Other signiicant performance characteristics are a sensitivity of 176 μA mM^-1 cm^-2 (deined as the slope of the current vs concentration plot at +0.4 V), a detection limit of 1.1 μM [signal-to-noise ratio (S/N) = 3], and a response time of 6 s.