Carbon-nanotube-modified glassy carbon electrode for simultaneous determination of dopamine, ascorbic acid and uric acid: the effect of functional groups

The effect of surface functional groups of multi-wall carbon nanotube (MWCNT) in MWCNT-modified glassy carbon electrode (MWCNT/GCE) on the simultaneous detection of ascorbic acid (AA), dopamine (DA), and uric acid (UA) was studied. Pristine MWCNT (MWCNT-P), acid-treated MWCNT (MWCNT-T), carboxyl-containing MWCNT (MWCNT-COOH), and hydroxyl-containing MWCNT (MWCNT-OH) were prepared and compared. The order of carbon content in the MWCNT was found to follow MWCNT-T < MWCNT-COOH < MWCNT-OH < MWCNT-P based on X-ray photoelectron spectroscopic (XPS) data. It was also found that sample MWCNT-T had the highest defect density but the lowest electrical resistance among the functionalized MWCNT based on the results of Raman spectroscopy and electrochemical impedance spectroscopy (EIS). The electrooxidation performance of the MWCNT/GCE toward simultaneous determination of DA, UA and AA in a ternary solution followed the order of MWCNT-T > MWCNT-COOH > MWCNT-OH > MWCNT-P. Based on the experimental results, the relationship between the electrocatalytic properties and the nature of functional groups of MWCNT was discussed.