CARBON NANOTUBE POWDER MICROELECTRODES FOR NADH OXIDATION

摘要

The carbon nanotube powder microelectrode (CNTPME) prepared from multi-wall carbon nanotubes (MWCNT) shows prominent and stable catalytic activity for NADH oxidation in pH 7 buffer. The activity is attributed to the quinonoid like surface groups which are formed electrochemically at potentials near -0.05 V (SCE) at surface of carbon nanotubes and act as mediators. Two waves due to NADH oxidation are observed on steady state polarization curves, corresponding to mediated and direct oxidation, respectively. A remarkable decrease (0.74 V) of overpotential for the mediated oxidation is found compared with that for glassy carbon electrodes. A model of meditative catalysis by surface redox couples is presented and the secondary rate constant for the mediation reaction is estimated to be 67 M~(-1)s~(-1). The sensitivity of CNTPME for NADH detection is ca. 91 mA cm~(-2)M~(-1) with a linearity ranging from 5 μM to 1 mM, 90% response time about 30 s and temperature coefficient 1.3%/℃ (15-40℃).