Enhanced voltammetric determination of dopamine using a glassy carbon electrode modified with ionic liquid-functionalized graphene and carbon dots

The authors describe a dopamine (DA) sensor based on a glassy carbon electrode modified with a composite film composed of carbon dots (C-dots) and graphene functionalized with an ionic liquid. The C-dots were functionalized with carboxy groups whose negative charge promotes electrostatic attraction to the protonated amino groups in DA. The presence of an imidazole cation in the IL facilitates interaction with the C-dots and DA via electrostatic interactions and π-stacking forces. Under optimal conditions, the modified GCE display improved electrochemical response to DA compared to a bare GCE, or a GCE modified with C-dots or IL-graphene only. The oxidation current, measured best at a potential of 0.22 V (vs. Ag/AgCl) is linearly related to the DA concentration in the 0.1 to 600 μM range, with a 30 nM detection limit at a signal-to-noise ratio of 3. Ascorbic acid does not interfere even in large excess, and the sensor is stable for at least a month. The modified GCE was applied to the determination of DA in spiked fetal bovine serum and gave satisfactory results.