Electrochemical sensing of heroin and related opiates using bimetallic Ni–Cu doped gallium oxide nanorods

Abstract

Heroin is a semi-synthetic morphine derivative that is misused extensively throughout the world. The speed, mobility, and sensitivity of current detection methods are frequently limited. Due to its ease of use, quick reaction time, and potential for on-site drug detection, electrochemical sensing presents a viable substitute. In this work, a novel and affordable Ni–Cu/Ga₂O₃ nanorod-based material was prepared for the electrochemical detection of heroin and opiates. TGA, SEM, TEM, XPS, and XRD were used to analyse the morphological and structural characteristics of the synthesised nanorods. Electrochemical impedance spectroscopy, differential pulse voltammetry, and cyclic voltammetry were used to examine their electrochemical behaviour. Because NiO and CuO show synergy, the Ni–Cu/Ga₂O₃ modified electrode showed a slightly enhanced electrochemically active surface area (0.02 cm²). The modified electrode showed a clear concentration-dependent response toward heroin over the range of 1–50 µM, with a linear range observed between 10 and 18 µM (R² = 0.9858). A practical detection limit of 2 µM was achieved, while the 3.3σ/S and 10σ/S methods yielded a 0.4 µM limit of detection and a 1.2 µM limit of quantification. Considering the rapid biotransformation of heroin in biological systems, the sensor's applicability in spiked serum and urine samples was evaluated using morphine and codeine as proxy analytes. Well-resolved oxidation peaks for codeine (∼1.1 V) and morphine (∼0.49 V) on the modified electrode enabled selective discrimination of structurally similar compounds. The presence of adulterants such as paracetamol, alprazolam, and caffeine showed a negligible to moderate effect on the detection of heroin. Overall, the developed Ni–Cu/Ga₂O₃ nanorods provide a simple, cost-effective, and reliable platform for opiate detection, with potential applications in forensic and biomedical analysis.