Fig. 4. (a) CV curves of LS–rGO/GCE in 0.1 M PBS (pH = 7.0) containing 100 μM DA at various scan rates (50–500 mV s⁻¹). (b) Plots of peak current (E_pa and E_pc) versus scan rate. (c) Plots of peak current (I_pa and I_pc) versus square root of scan rate in the range of 50–300 mV s⁻¹. (d) Plots of peak current (I_pa and I_pc) versus scan rate in the range of 300–500 mV s⁻¹.