Electrochemical Sensors Based on Flexible Laser-Induced Graphene for the Detection of Paraquat in Water

Abstract

Paraquat (PQ) is known to be highly toxic among herbicides and harmful to human health upon exposure because it causes various kinds of organ failure and affects the nervous system. Nowadays, increasing concentration of PQ in water bodies is a growing concern among many countries. On-site-based detection is very needed along with selectivity and sensitivity, which can be achieved through an electrochemical-based sensor. In this paper, a flexible laser-induced graphene (LIG)-based electrode was developed for the effective detection of PQ by the electrochemical square-wave-voltammetry (SWV) method. LIG is a 3D porous material fabricated by patterning with the help of CO2 laser irradiation on polyimide (PI) films and has extensive properties such as high conductivity, biocompatibility, and high porosity. LIG was further treated in a phosphate buffer solution to obtain treated LIG (t-LIG). The surface morphology and carbon fingerprint of both LIG and t-LIG were then characterized using scanning electron microscopy (SEM) and Raman spectroscopy, where SEM images have shown a more exposed porous structure in t-LIG. Electrochemical characterization was carried out using cyclic voltammetry and revealed a good current response and more surface activation of t-LIG over LIG. The detection of PQ carried out using t-LIG by the SWV method showed a high linear range of 0.5–35 μM with a sensitivity of 46.6 μA μM–1 cm–2 and a limit of detection of 0.54 μM. t-LIG has shown a very good average recovery rate of PQ when spiked in real water samples of 96.6%.