The effect of N-configurations on selective detection of dopamine in the presence of uric and ascorbic acids using surfactant-free N-graphene modified ITO electrodes

Highlights: • Novelty in this paper thus resides in:1)Use of a surfactant free method, in which flims of N-doped graphene are the electroactive material. 2)The correlation of the type of N doping with the electrochemical activity for dopamine detection. 3)Illustration that i) graphitic N and ii) pyridinic N do not correlate with activity. Both iii) pyrrolic N and iv) NOx groups, by contrast, do show correlation. • Our study indicates a facile process for making electrodes in which films with different compositions can be made and evaluated. The extension with dopamine suggests that the process can be generalised to many other bioactive and non-bioactive molecules. Nitrogen doped graphene based electrodes are increasingly gaining attention for application in voltammetric detection of dopamine (DA). However, little attention has been paid on the influence of the relative concentration of N-configurations on the electrocatalytic performance of these electrodes. Therefore in this study, sensitive and selective surfactant-free indium tin oxide (ITO) electrodes, modified with N-graphene films of varying nitrogen configurations, were employed for detection of DA in the presence of uric (UA) and ascorbic acids (AA). The N-graphene films, initially characterized using XPS, consisted of 38–60% pyridinic-N, 4–31% pyrrolic-N, 13–56% graphitic-N, and 2–9% oxidized pyridinic-N (NOx). The results showed that the NGr/ITO electrodes exhibited excellent selective electrocatalytic performance for the oxidation of DA in the presence of UA and AA. As a result, the detection limits (S/N = 3) of DA were determined to be 0.131 ± 0.005 μM, 0.153 ± 0.03 μM, and 0.645 ± 0.07 μM at the NGr-2/ITO, NGr-10/ITO and NGr-20/ITO electrodes, respectively. The excellent electrocatalytic activity of NGr-2/ITO electrode towards the oxidation of DA was ascribed mainly to an improved π-π interaction of the NOx (9.2%) and pyrrolic N-configurations (59.6%) with the hydroxyl and amine groups on DA. Generally, this study has provided a procedure for designing new surfactant-free 2D N-graphene based electrochemical sensors with specific electrocatalytic performance.