An electrochemical sensor based on cobalt oxyhydroxide nanoflakes/reduced graphene oxide nanocomposite for detection of illicit drug-clonazepam

Clonazepam (CNZ) is a commonly prescribed drug for the management of mental illness including insomnia, panic anxiety and status epilepsy. Due to the associated sedative effects, CNZ has also become a drug of abuse amongst addicted users, sexual assault cases, and suicide. Therefore, it becomes vital to analyze CNZ in human specimens for criminal investigational purposes. Herein, we report the construction of an electrochemical sensor based on self-assembled hybrid nanocomposite of 2-D transition metal oxide nanoflakes i.e., cobalt oxyhydroxide (CoOOH) nanoflakes and reduced graphene oxide (rGO) for determination of clonazepam (CNZ), especially in different beverages. The physico-chemical characterization of the as-synthesized hybrid nanocom-posite was done by scanning electron microscopy (SEM), X-Ray diffraction (XRD), raman spectroscopy, X-ray photoelectron spectroscopy (XPS), fourier transform infrared spectroscopy (FTIR) and UV-Visible spectroscopy. Further, the surface of the screen printed carbon electrode (SPCE) was modified with CoOOH-rGO hybrid nanocomposite and its electrochemical characteristics were evaluated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) techniques. A synergistic combination of CoOOH nano -flakes with abundant catalytic sites and highly supportive skeletons of rGO nanosheets that act as conductive bridges for charge transfer makes the nanocomposite sensor unique for electrochemical detection. Under optimized conditions, the specific interaction of CNZ with CoOOH-rGO modified SPCE was determined by differential pulse voltammetry (DPV) to measure the dose dependent increase in reduction current values at a potential of 0.11 V. The developed sensor achieved a detection limit of 38 nM with a sensitivity of 0.054 mu A mu M-1 cm(-2) over a dynamic concentration range of 0.1-350 mu M. Moreover, the sensor was applied for determination of CNZ in spiked beverages samples and showed satisfactory recovery in the range of 87-115%. This work provides a new avenue for the development of hybrid nanocomposites based electrochemical sensing platforms for on-site screening of illicit drugs, as necessitated for forensics and clinical settings.

Automated summary

In this study, an electrochemical sensor based on self-assembled hybrid nanocomposite of cobalt oxyhydroxide nanoflakes and reduced graphene oxide was developed for the determination of clonazepam in different beverages. The sensor showed high sensitivity and reliable detection limit, making it suitable for on-site screening of illicit drugs in clinical and forensic settings.