3D-printed electrochemical sensor based on graphite-alumina composites: A sensitive and reusable platform for self-sampling and detection of 2,4,6-trinitrotoluene residues in environmental and forensic applications

The detection of explosives is of great importance in the forensic scenario. For this reason, we proposed a lab-made graphite/alumina/polylactic acid (G/Al₂O₃/PLA)-based 3D-printed electrode for 2,4,6-trinitrotoluene (TNT) electrochemical determination. The material was characterized by infrared and Raman spectroscopy, scanning electron microscopy, and energy dispersion X-ray spectra, indicating that G and Al₂O₃ were incorporated into the PLA matrix. The proposed electrode combined with the square wave voltammetry (SWV) technique, demonstrated the ability to detect TNT residues, where the first reduction process around -0.24 V was monitored for the analyses. The developed electrochemical strategy supplied a linear range between 0.5 – 6.0 µmol L^-1 and a detection limit of 0.071 µmol L^-1. The method's applicability was tested on real samples of tap, lagoon, and seawater by direct analysis. Recovery values in the 100 to 106% range were obtained, representing adequate accuracy. The lab-made electrode was also utilized as a sampler to collect TNT residues on different surfaces, enabling the detection of TNT levels in the nanogram range and demonstrating the electrode's exceptional ability to detect trace amounts of the compound. These results reinforce the device's potential as a viable alternative for fast, accurate, and low-cost analysis in practical situations.