Electrochemical sensor for detecting dopamine using graphene quantum dots incorporated with multiwall carbon nanotubes

A ratiometric electrochemical biosensor was developed for dopamine detection based on the incorporation of graphene quantum dots (GQDs) with acid-functionalized multiwall carbon nanotubes (MWCNTs) on a glassy carbon electrode (GCE) surface. The GQDs@MWCNTs/GCE nanocomposite was characterized by XRD, SEM, TEM, AFM, XPS, and electrochemical techniques. The UV absorbance peak of GQDs was located at 235 nm, and the average size of the GQDs was 1–5 nm. The electrochemical responses indicated that the proposed sensor exhibited good electrocatalytic activity toward the oxidation of dopamine and spiked dopamine, over a dynamic linear range of 0.25–250 μM, with low detection limits of 95 nM and 110 nM (S/N = 3), respectively. In addition, the developed sensor interacted selectively with dopamine rather than other molecules was investigated using an amperometric technique. The developed sensor exhibited excellent reproducibility, selectivity, and sensitivity.