Forensic electrochemical sensor for fentanyl and morphine detection using an Au–NiOx-electrodeposited carbon electrode

Abstract

The overuse and abuse of narcotics, such as fentanyl and morphine, has resulted in serious threats to human health. Although current detection methods are generally effective, they rely on specialized laboratory equipment. Herein, a forensic electrochemical sensor was developed for the on-site detection of trace quantities of fentanyl and morphine. A screen-printed carbon electrode (SPCE) was modified via the electrodeposition of Au and nickel oxide (NiO_x) to enhance its electrochemical activity. Au electrodeposition was performed using a multi-potential step method that alternated between deposition and resting potentials (−0.2 and 0.7 V, respectively) with pulse durations of 1 s and 500 ms, respectively. Subsequently, NiO_x deposited onto the Au–SPCE by applying a constant potential of −1.0 V for 1 h resulted in uniform NiO_x nanofilms on the three-dimensional leaf-shaped Au structure, as observed by focused ion beam scanning electron microscopy. In addition, X-ray diffraction and photoelectron spectroscopy analyses confirmed the presence and chemical states of Au and NiO_x on the SPCE surface. The electrochemical sensing performance of the modified SPCE was evaluated using linear sweep voltammetry, which revealed detectable signals at 0.85 and 0.5 V for fentanyl and morphine, respectively. Moreover, the calibration curves exhibited a linear relationship between concentration and current density, thereby confirming the sensitivity of the sensor electrode. The distinct oxidation peak potentials enabled the simultaneous detection of fentanyl and morphine in mixed solutions, confirming its selectivity for target molecules. The findings of this study demonstrate the potential of Au–NiO_x-modified SPCEs as a practical tool for rapid and selective electrochemical detection of narcotic substances.