Tungsten Selenide Quantum Dot-Based Electrocatalytic Detection of Lamivudine

Abstract

Lamivudine (LAM) is an antiviral drug used against hepatitis, human immunodeficiency virus, and acquired immunodeficiency syndrome. Due to the increasing occurrence of antiviral drugs in wastewaters around the globe, and the health hazards and risks associated with the inherent human and ecosystem exposure, researchers have taken advantage of the reactivity of these antiviral drugs and their affinity to form various bonds with novel nanoparticles, to foster more convenient and environmentally friendly methods of wastewater monitoring of antivirals using nanomaterials in sensor fabrication. The deviation from the conventional methods of wastewater monitoring seeks to overcome the inefficiency, tediousness, and complexity of sample preparation of the conventional methods. In the current research work, a colloidal synthesis method was developed and used to synthesize L-cysteine-functionalized tungsten diselenide quantum dots (L-cyst-WSe₂QDs) for the monitoring of LAM in water. Characterization of nanoparticles was done using different spectroscopy methods, transmission electron microscopy (TEM), and X-ray diffraction (XRD) patterns. Successful capping and functionalization of QDs was demonstrated by Fourier-transform infrared spectroscopy. Small-angle X-ray scattering and zetasizer analytical studies corroborated the formation of QDs of sizes less than 10 nm. High-resolution TEM, XRD, and small-angle electron diffraction confirmed the highly crystalline nature of the QDs. The L-cyst-WSe₂QDs were bound by Nafion to a preactivated glassy carbon (GC) electrode, and the fabricated sensor exhibited excellent electrochemical sensing efficiency as compared to previously reported WSe₂ sensors and other various sensors used to detect LAM, presenting high sensitivity and good selectivity with the lowest reported limit of detection (LOD) of 0.1 nM using the square wave voltammetry (SWV) technique in wastewater effluents. This work provided a lower LOD than previous reports on electrochemical sensing of LAM using differential pulse voltammetry and SWV. Though the electrochemical behavior of LAM on L-cyst-WSe₂QDs/GC was established for the first time through this current study, LAM was irreversibly reduced at negative potentials, validating a previously established characteristic response. The sensor exhibited high reproducibility with an excellent stability by retaining 87.2% sensor functionality and stability after 7 days. The reduction peak current of LAM presented a linear range of 2–10 pM with a correlation coefficient of 0.993. The application of the LAM sensor in the determination of LAM in real wastewater samples exhibited excellent recoveries ranging between 94.6% and 99.9%, thereby demonstrating the suitability of the sensor for application in real time.