Carbon nanotube powder microelectrodes for nitrite detection

Multi-wall carbon nanotubes (MWCNTs) are filled in the cavity at the tip of a microelectrode to form a carbon nanotube powder microelectrode (CNTPME) for testing the nanotubes under various conditions. Anodic treatment is found to cut the nanotubes into shorter species, increase double layer capacity, and make the nanotubes able to strongly adsorb Os(bpy)32+. The CNTPME modified with anodic pretreatment and pre-adsorbed Os(bpy)32+ (CNTPME-Os(bpy)32+) shows high catalytic activity for nitrite reduction in acidic solutions. The sensitivity, temperature coefficients of such modified electrode for nitrite detection are 4.9 and 6.8 A cm−2 M−1, 0.14 and 0.16% (°C)−1 for steps 1 and 2 of nitrite reduction, respectively with a lower detection limit 10−7 M for S/N=4. These features plus the miniaturizability make the CNTPME-Os(bpy)32+ a very promise candidate for nitrite sensor.