Intrinsic peroxidase-like activity of graphene nanoribbons for label-free colorimetric detection of dopamine.

Graphene nanoribbons (GNR) with intrinsic peroxidase mimic activity were introduced as a nanozyme with catalytic activity in oxidation of a typical chromogenic peroxidase substrate, 3,3',5,5'-tetramethylbenzidine (TMB), in the presence of H2O2. The proposed artificial enzyme was used as a label-free biosensor for rapid and sensitive colorimetric detection of dopamine (DA) according to a blue color fading which occurred due to the inhibition of TMB oxidation. Attractively, GNR exhibited an excellent catalytic activity over other carbon-based nanostructures due to its unique and extraordinary structural properties. Considering the changes of A653 versus DA concentration, a good linear dependency was achieved in the concentration range of 0.1-50 μM (0.1-1 and 2.5-50 μM) with a detection limit of 0.035 μM. The present peroxidase mimetic as a simple and rapid label-free sensor was successfully applied for detection of DA in serum samples, suggesting a promising sensitive sensing platform with great potential for biological and diagnostic applications.