Selective Detection of Trace Nitroaromatic, Nitramine, and Nitrate Ester Explosive Residues Using a Three‐Step Fluorimetric Sensing Process: A Tandem Turn‐off, Turn‐on Sensor*

Abstract

Detection of trace quantities of explosive residues plays a key role in military, civilian, and counter-terrorism applications. To advance explosives sensor technology, current methods will need to become cheaper and portable while maintaining sensitivity and selectivity. The detection of common explosives including trinitrotoluene (TNT), cyclotrimethylenetrinitramine, cyclotetramethylene-tetranitramine, pentaerythritol tetranitrate, 2,4,6-trinitrophenyl-N-methylnitramine, and trinitroglycerin may be carried out using a three-step process combining "turn-off" and "turn-on" fluorimetric sensing. This process first detects nitroaromatic explosives by their quenching of green luminescence of polymetalloles (lambda em approximately 400-510 nm). The second step places down a thin film of 2,3-diaminonaphthalene (DAN) while "erasing" the polymetallole luminescence. The final step completes the reaction of the nitramines and/or nitrate esters with DAN resulting in the formation of a blue luminescent traizole complex (lambda(em) = 450 nm) providing a "turn-on" response for nitramine and nitrate ester-based explosives. Detection limits as low as 2 ng are observed. Solid-state detection of production line explosives demonstrates the applicability of this method to real world situations. This method offers a sensitive and selective detection process for a diverse group of the most common high explosives used in military and terrorist applications today.

Current trends in explosive detection techniques

“…This group's work was continued to make the sensor more selective by incorporating a tandem process that first quenches the metallole in the presence of nitroaromatics as described above. A thin film of 2,3-diaminonaphthalene (DAN) is then applied which cancels the polymetallole luminescence and, in the presence of nitroamine and/or nitrate-ester explosives, a reaction with the DAN forms a blue luminescent complex[98]. An investigation into synthesising polymers and copolymers and their relevance to explosive detection was also undertaken by this group which reported some polymers were able to detect nitroaromatic, nitro-amine and nitro-ester explosive compounds[99].…”

Turn-off luminescence sensing, white light emission and magnetic studies of two-dimensional lanthanide MOFs

“…[38][39][40][41][42][43] Thus, many harmful ions such as arsenate and chromates, as well as organic molecules including pesticides, explosives, etc., have been detected by the use of turn-off luminescence behaviour. [44][45][46][47][48][49][50][51][52][53] Along this line, we have reported 2D and 3D framework compounds assembled from Ln(III) ions and 2,5-bis( prop-2-yn-1-yloxy)terephthalic acid (2,5-BPTA) that exhibited luminescence and catalytic properties. 54 In these compounds, the coordination spheres of the Ln ions contained H 2 O as a ligand, which is not ideal for luminescence efficiency.…”

“…38–43 Thus, many harmful ions such as arsenate and chromates, as well as organic molecules including pesticides, explosives, etc ., have been detected by the use of turn-off luminescence behaviour. 44–53…”

Ratiometric Turn-On Fluorophore Displacement Ensembles for Nitroaromatic Explosives Detection

“…[7][8][9][10][11][12][13][14][15][16][17][18] Although so-called "turn-on" emission-based sensing is highly desirable due to its higher intrinsic sensitivity and better chemical selectivity, [18][19][20] it is a truism that nearly all reported small molecule fluorescence sensing systems for the nitroaromatic explosives, such as 2,4,6-trinitrotoluene (TNT) and 2,4-dinitrotoluene (DNT), rely on quenching of the emission intensity of one or more fluorophores. [7][8][9][10][11][12][13][14][15]21 An important exception is a turn-on system that responds to 2,4,6trinitrophenol (TNP), a highly acidic analyte. [22][23][24] The lack of small molecule turn-on sensors for most nitroaromatic compounds (NACs) likely reflects the favorable nature of photoinduced electron/energy/charge transfer between various putative emitters and the electron-deficient NACs, leading to strong quenching.…”