Zinc Oxide/Laser-Induced Graphene Matrix Electrochemical Impedance Spectroscopy Assisted Toluene Detection in Liquid Phase

Abstract The effect of toluene on the environment needs to be studied as it may cause problems for aquatic life, agriculture, and human health. Monitoring the toluene level is necessary to take the necessary steps. A flexible working electrode was modified with the metal oxide nanoparticle (ZnO) as an active site for electrochemical activity. The material characterization was carried out with scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, and X-ray diffraction (XRD). The electrochemical impedance spectroscopy (EIS) method was used for the detection and optimization of the sensor, and the constant phase elements (CPEs) were analyzed. Furthermore, the concentration effect was analyzed between a linear range of 100 nM and 0.1 mM. The sensor showed good linearity with a limit of detection (LoD) of 97.2 nM and a limit of quantification (LoQ) of 252.36 nM. The interference study used the equivalent circuit parameter with constant phase element analysis. The surface behaves as the constant phase element instead of double-layer capacitance. The real sample analysis was carried out using tap water. The fabricated electrode showed good selectivity and appreciable recovery values in real-time samples. Owing to the conclusions drawn, the fabricated electrode is expected to show a great potential for real-time application. In further, volatile organic compounds (VOCs) being sensitive to environment, this study is a prototype for development of miniaturized sensors for VOCs monitoring.