Utilization of a Selective Paper-Based Flexible Electrochemical Sensor for Epinephrine Determination in Artificial Sweat Using Nickel Oxide and Sulfur-Doped Graphene Conductive Ink

Abstract Epinephrine (adrenaline, EP) is a crucial hormone that regulates the body's response to emergencies. During periods of stress or danger, it is responsible for rapidly mobilizing the body by elevating heart rate, blood pressure, and respiratory rate. Consequently, the accurate and rapid measurement of EP is of significant importance. In this study, sulfur-doped graphene (S-Gr) synthesized using Yucel’s method, and nickel oxide (NiO) were utilized as conductive materials to develop conductive inks. Furthermore, a paper-based flexible electrochemical sensor was constructed for EP determination. The optimum conductive ink for sensor fabrication was identified through optimization process. The sensor was characterized using various techniques, including cyclic voltammetry, electrochemical impedance spectroscopy, field-emission scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction analysis, and Fourier transform infrared spectroscopy. The sensor demonstrated a detection limit of 33.16 nM, and its cost-effective and user-friendly design renders it an advantageous option for practical applications. The results obtained from the analytical studies indicated that the sensor exhibits high selectivity towards EP and can successfully detect EP in artificial sweat samples. In conclusion, the proposed sensor serves as a model for future flexible and wearable devices.