Label-Free Detection of 2,4-Dinitrotoluene Using a Laser-Induced Graphene Based Chemiresistive Sensor

The rapid and sensitive detection of nitroaromatic explosives is of paramount importance for both security and environmental monitoring. In this study, a label-free chemiresistive sensor based on laser-induced graphene (LIG) was developed for the selective detection of 2,4-dinitrotoluene (DNT). LIG films were directly fabricated on polyimide substrates via a single-step laser writing process, resulting in porous and conductive surfaces without additional modification. The structural, chemical, and electrical properties of the fabricated materials were comprehensively evaluated using scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS). The electrical properties were characterized by current-voltage (<i>I</i>-<i>V</i>) measurements using a Kelvin (pseudofour-point) configuration. SEM revealed a porous morphology formed during laser scribing, while XRD and Raman spectroscopy confirmed multilayer graphene (∼5 layers) with relatively low defect density. FTIR spectroscopy indicated residual oxygen-containing functional groups, and XPS verified DNT adsorption. The fabricated films exhibited a uniform electrical conductivity of 1545 S/m. By employing these films, a chemiresistive sensor was developed, which demonstrated a response toward DNT, achieving an estimated detection limit (LOD) of 3.79%, corresponding to 2.4 × 10^-9 M. Strong selectivity was observed against structurally related interferents such as nitrotoluene, toluene, and ethanol. These results demonstrated that LIG-based flexible sensors provide a low-cost, scalable, and selective platform for explosive detection with promising applications in security and environmental monitoring.