Electrochemical impedimetric analysis of different dimensional (0D-2D) carbon nanomaterials for effective biosensing of L-tyrosine

Electrochemical biosensors employing nano-transduction surfaces are considered highly sensitive to the morphology of nanomaterials. Various interfacial parameters namely charge transfer resistance, double layer capacitance, heterogeneous electron transfer rate and diffusion limited processes, depend strongly on the nanostructure geometry which eventually affects the biosensor performance. The present work deals with a comparative study of electrochemical impedance-based detection of L-tyrosine (or simply tyrosine) by employing carbon nanostructures (graphene quantum dots, single walled carbon nanotubes (CNTs) and graphene) along with tyrosinase as the bio-receptor. Specifically, the role of carbon nanostructures (i.e. 0D, 1D and 2D) on charge transfer resistance is investigated by applying time-varying electric field at the nano-bioelectrode followed by calculating the heterogeneous electron transfer rate, double layer capacitor current and their effects on limits of detection and sensitivities towards tyrosine recognition. A theoretical model based on Randel's equivalent circuit is proposed to account for the redox kinetics at various carbon nanostructure/enzyme hybrid surfaces. It was observed that, the 1D morphology (single walled CNTs) exhibited lowest charge transfer resistance similar to 2.62 k omega (lowest detection limit of 0.61 nM) and highest electron transfer rate similar to 0.35 mu m s(-1) (highest sensitivity 0.37 k omega nM(-1) mm(-2)). Our results suggest that a suitable morphology of carbon nanostructure would be essential for efficient and sensitive detection of tyrosine.