Electrochemical behaviour of ABTS on aryl-modified glassy carbon electrodes

The electrochemical response of 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) on aryl-modified glassy carbon (GC) electrodes has been investigated. The electrochemical modification of GC surface with 4-nitrophenyl (NP) and 4-carboxyphenyl (CP) groups was performed using the diazonium reduction method. The 4-aminophenyl-modified GC electrodes were obtained by electroreduction of NP films. The surface coverage of aryl groups was altered by varying the number of potential scans during electrografting experiments. The electrochemical behaviour of ABTS was studied on bare and aryl-modified GC electrodes using cyclic voltammetry and the rotating disk electrode (RDE) methods. Electrochemical measurements were performed in acetate and phosphate buffers (pH = 4–8) to study the effect of pH on the electron transfer process. The response of ABTS was independent of pH for bare GC and GC/NP electrodes (modified by 20 electrografting scans), whereas a slight pH-dependence was observed for other electrodes. The strongest blocking action was observed for the NP-modified GC electrodes of higher surface coverage and the lowest for reduced NP films (modified by a single electrografting scan).