Preconcentration techniques for trace explosive sensing

Abstract

Trace sensing of explosive vapours is a method in humanitarian demining and Improvised Explosives Device (IED) detection that has received increasing attention recently, since accurate, fast, and reliable chemical detection is highly important for threat identification.However, trace molecule sampling in the field can be extremely difficult due to factors including weather, locale, and very low vapour pressure of the explosive. Preconcentration of target molecules onto a substrate can provide a method to collect higher amounts of analyte for analysis. We used the commercial fluoropolymer Aflas as a preconcentrator material to sorb explosive molecules to the surface, allowing subsequent detection of the explosives via the luminescence quenching response from the organic polymer Super ACCEPTED MANUSCRIPTHighlights  Trace detection of explosive vapours is challenging in real-world environments. By "preconcentrating" trace vapours onto solid substrates, higher amounts can be collected for detection. Our approach combines fluoropolymer preconcentrators, free-flying honeybees for sampling, and luminescent thin films as the sensing mechanism. The inexpensive, commercially-available fluoropolymer Aflas has shown good preconcentration abilities for 2,4-DNT which is typically found in landmines. Laboratory results and initial field results indicate this method is a very promising tool for the detection of trace explosive vapours in contaminated land.

Bioindicators and biomonitoring: honeybees and hive products as pollution impact assessment tools for the Mediterranean area

“…Recently, Gillanders et al (2019) developed a special detection method for explosive residues. The main hurdle to explosive detection is obtaining a sufficient amount of analyst for analysis, so the Authors placed strips containing a commercial fluoropolymer (AFLAS) in the entrances to the beehives.…”

Explosives detection by swabbing for improvised explosive devices

“…26 Sensor films were based on the polymer Merck Super Yellow, which is a commercially-available conjugated polymer that has been shown recently to be an effective sensor of explosives including 2,4-DNT and TNT. 19,27,28 Super Yellow was dissolved in toluene at a concentration of 6.5 mg ml −1 . Glass slides were cleaned by ultrasonication in toluene, acetone and propan-2-ol, and then dried and plasma ashed in a 100% oxygen plasma (Plasma Technology MiniFlecto) at a pressure of 0.2 mbar.…”

“…Samples were stored in the dark in a nitrogen glove-box environment with 0% humidity and <10 ppm oxygen when not in use to avoid any degradation of the films. The photophysics and optical characterisation have been described in previous studies 13,19,28 but briefly, the excitation wavelength of Super Yellow is 440 nm, the peak emis- sion wavelength 590 nm, and the photoluminescence quantum yield (PLQY) is 40% in a film in ambient conditions.…”

“…An inexpensive fluoropolymer of ∼56% tetrafluoroethylene, ∼27% vinylidene fluoride and 17% propylene, with the trade name Aflas (Fig. 1b), has recently been shown to passively sorb and thermally desorb explosives on test minefields, 19 and has also shown good sorption capabilities for Volatile Organic Compounds (VOCs). 20 Polymers of similar structure have been used in the past for explosives concentration, [21][22][23] as have graphite sheets 24 and 3D-printed devices, 25 though Aflas is an inexpensive, easily-processed, commercially-available solution for the type of large-batch processing required for humanitarian and security-based applications.…”

“…In a previous minefield-based study with Aflas, air was sampled from a bee colony free-flying over contaminated land, and Aflas-coated papers were inserted into the colony entrance to accumulate explosive molecules from the honeybee bodies. 19 In the scenario outlined in this work, the same preconcentrators can potentially be deployed for IED detection by physical wiping of the contaminated surface.…”