3D-porous laser-scribed graphene decorated with overoxidized polypyrrole as an electrochemical sensing platform for dopamine

The authors present in this work, a novel, simple, and disposable electrochemical sensor for the detection of dopamine (DA). Indeed, the proposed sensing system is based on overoxidized polypyrrole (PPy_ox) modified laser scribed graphene electrode (LSGE). LSGEs were fabricated via direct laser-writing on polyimide (PI) sheets to produce a 3D-porous structure of graphene that offers a large conducting surface area. The morphology of the electrode surface was analyzed using scanning electron microscopy (SEM). The electrochemical behavior of the developed sensor was investigated using cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). Compared to conventional screen-printed carbon electrodes, the results showed that the current responses of DA were drastically enhanced due to the excellent catalytic activity of the LSGE as well as the strong electrostatic attraction of the deposited PPy_ox film that enables a selective accumulation of DA into the sensor's surface. Furthermore, this sensing strategy demonstrated outstanding adsorption features toward DA detection leading to the detection of subnanomolar levels via preconcentration at an open circuit potential (OCP) system. Under optimal conditions, two linear calibration plots were established in the range of 0.5 µM–10 µM at a close circuit potential and 10 nM–500 nM under 5 min of preconcentration at OCP with a lower limit of detection estimated to be 7 nM. The developed sensor demonstrated good selectivity, adaptability, and stability. As a result, it was effectively employed for the detection of DA in human blood serum and tap water samples, with satisfactory recovery values.