3.1. Modification of GC electrode with 2-TBI
The two irreversible oxidation peaks show the electrochemistry of 2-TBI on bare GC electrode at 1490 mV and 1820 mV (Fig. 1). The less positive peak is characteristic of the oxidation that occurred on the nitrogen atom in the imidazole ring [37]. The currents of both irreversible oxidation peaks decreased with increasing number of potential cycles. After a few cycles the currents reached a steady-state condition. The formation of the 2-TBI layer on GC surface is explained with the differential decrease of the peak current. The GC surface is oxidized when the switching potential is extended to the oxygen-evolution potential range and giving rise to the formation of carboxylic and alcoholic functionalities [7]. These oxygen-containing functionalities probably come from the residual water present in MeCN, which has been reported as approximately in the range of 10− 3 to 10− 2 M [38], almost at the same level with or more than the 2-TBI species. Therefore, the modification is a reaction between the surface hydroxyl functionalities with the oxidation product of the 2-TBI compound through the aromatic p-carbon, resulting in etheric bond (GC)Csingle bondOsingle bondC(2-TBI).