Carbon nanotube detectors for microchip CE: Comparative study of single‐wall and multiwall carbon nanotube, and graphite powder films on glassy carbon, gold, and platinum electrode surfaces

Abstract

The performance of microchip electrophoresis/electrochemistry system with carbon nanotube (CNT) film electrodes was studied. Electrocatalytic activities of different carbon materials (single‐wall CNT (SWCNT), multiwall CNT (MWCNT), carbon powder) cast on different electrode substrates (glassy carbon (GC), gold, and platinum) were compared in a microfluidic setup and their performance as microchip electrochemical detectors was assessed. An MWCNT film on a GC electrode shows electrocatalytic effect toward oxidation of dopamine (E_1/2 shift of 0.09 V) and catechol (E_1/2 shift of 0.19 V) when compared to a bare GC electrode, while other CNT/carbon powder films on the GC electrode display negligible effects. Modification of a gold electrode by graphite powder results in a strong electrocatalytic effect toward oxidation of dopamine and catechol (E_1/2 shift of 0.14 and 0.11 V, respectively). A significant shift of the half‐wave potentials to lower values also provide the MWCNT film (E_1/2 shift of 0.08 and 0.08 V for dopamine and catechol, respectively) and the SWCNT film (E_1/2 shift of 0.10 V for catechol) when compared to a bare gold electrode. A microfluidic device with a CNT film‐modified detection electrode displays greatly improved separation resolution (R_s) by a factor of two compared to a bare electrode, reflecting the electrocatalytic activity of CNT.