This study introduces a novel approach for detecting
2,4,6-trinitrotoluene
(TNT) explosives using a pencil-based sensor. The sensor utilizes
the circular area of a 3 mm diameter pencil lead enclosed by a wooden
shaft as the working electrode. Graphene and silver–silver
chloride inks are printed onto transparent sticky tapes, as the counter
and reference electrodes, respectively. These tapes are affixed to
the pencil body, with copper wires as electrical conductors. Differential
pulse adsorptive stripping voltammetry of standard TNT solutions (0.5–30
mg L–1) in 0.5 mol L–1 NaCl reveals
two distinct peak signals at −0.46 and −0.64 V, along
with a smaller peak at −0.75 V. The identification of TNT in
a sample is confirmed by comparing the ratios of these three peak
currents with those of standard TNT. The detection of TNT in the field
is achieved by employing the pencil sensor in conjunction with drone
sampling. The drone is equipped with four sampling devices, each housing
a “gel-electrolyte adsorbent” attached to its landing
gears. The gel effectively absorbs TNT residues upon landing on suspicious
targets. In situ detection with the gel-medium yields a limit of detection
(LOD) of 4.8 mg L–1 TNT for standard solutions.
Our method demonstrates the efficacy of the pencil sensor for on-site
and rapid analysis (2.3 min). Following drone sampling, field detection
yields a LOD of 0.026 ng cm–2 TNT. This method proves
suitable for remote security screenings in areas of terrorist activities
and war zones.