How Science Helped Detect The Powerful Explosive TATP In Unidentified Objects

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Triacetone triperoxide (TATP) is a powerful explosive without military use because it is very sensitive to mechanical shock and so very difficult to safely handling, a reason for which terrorists dubbed TATP “the Mother of Satan”.

TATP is easily prepared from acetone and hydrogen peroxide under acidic catalysis, being a home-made explosive almost undetectable by dogs or sniffer devices usually trained for nitrogen-containing explosives. The possibility of being prepared on board gave rise to restrictions on carrying liquids in hand luggage at airports, and the careful monitoring of luggage and people, so TATP is presently one of the substances with more impact in the everyday life of millions of people who probably never heard about its existence. TATP is frequently used in suicide terrorist attacks, therefore constitutes a threat in public transport or mass events where prevention of indiscriminate attacks with explosives is a major concern.

Manufacturers of explosive detectors tend to concentrate on X-rays for bulk materials, but the signature of TATP is not clearly visible except by bulky mass spectrometers. A consequence of this is that better systems still need to be developed. Looking for much simpler technologies, optical portable methods have been developed on the basis of colorimetric or fluorimetric sensor arrays for detection of TATP vapor, by detecting hydrogen peroxide from TATP decomposition, because TATP itself did not react with the probes. So the search for fluorogenic probes that are specific for TATP is still an unresolved problem required for the easy and portable detection of peroxide explosives in checking of unknown materials at police controls.

The ideal probe should have a strongly fluorescent reporter and a quenching group easily oxidizable by a mild oxidizing reagent in the absence of any solvent. Perylenediimides (PDIs) are strongly fluorescent compounds of known stability under light and air, suitable for high-value dendrimeric materials in bioimaging and gene delivery applications, therefore they are appropriate candidates for the reporter unit. Our approach consisted of a modification of a fluorescent perylenediimide core with one electron donor aryl group by the classic carbon-carbon coupling chemistry.

From the study of its physicochemical characteristics, its sensitivity to oxidants and its covalent anchoring to a polymer we have developed a fluorogenic material that was able to generate fluorescence in the presence of triacetone triperoxide, TATP, under solvent-free, solid-state conditions. The material, a perylenediimide functionalized polyacrylate, worked by accumulating vapors of TATP, giving a colorimetric and strongly fluorescent response. The fluorescent response given by the material to the presence of TATP was permanent so it could be checked at any time after the TATP exposition. With the membrane, we developed an easy “white powder test” to detect solid TATP from suspect packages containing ‘white powder’ that could be involved in unidentified threats.

In a typical experiment, a polymer piece from a vial with TATP acquired a strong orange fluorescence and pink color whilst an unreacted piece was non-fluorescent and purple colored, indicating the unequivocal presence of TATP in the white powder.

This study, Solvent-Free Off–On Detection of the Improvised Explosive Triacetone Triperoxide (TATP) with Fluorogenic Materials was recently published in the journal Chemistry – A European Journal.

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