Sarah J. Toal

Polymer sensors for nitroaromatic explosives detection

Several polymers have been used to detect nitroaromatic explosives by a variety of transduction schemes. Detection relies on both electronic and structural interactions between the sensing material and the analyte. Quenching of luminescent polymers by electron deficient nitroaromatic explosives, such as trinitrotoluene, may be monitored to detect explosives. Resistive sensing using carbon black particles that have been coated with different organic polymers and deposited across metallic leads can also be used to detect nitroaromatic vapors in an electronic nose approach. Frequency changes in surface acoustic wave devices may be monitored to detect nitroaromatics after their adsorption into polymer coatings. Luminescent polymetalloles have recently been investigated for sensing explosives in aqueous-based solutions and for improved visual detection of trace particulates on surfaces.

Visual detection of trace nitroaromatic explosive residue using photoluminescent metallole-containing polymers.

ABSTRACT: The detection of trace explosives is important for forensic, military, and homeland security applications. Detection of widely used nitroaromatic explosives (trinitrotoluene [TNT], 2,4‐dinitrotoluene [DNT], picric acid [PA]) was carried out using photoluminescent metallole‐containing polymers. The method of detection is through the quenching of fluorescence of thin films of the polymer, prepared by spray coating organic solutions of the polymer, by the explosive analyte. Visual quenching of luminescence (λem≈400–510 nm) in the presence of the explosive is seen immediately upon illumination with near‐UV light (λex=360 nm). Detection limits were observed to be as low as 5 ng for TNT, 20 ng for DNT, and 5 ng for PA. In addition, experiments with normal production line explosives and their components show that this technology is also able to detect composition B, Pyrodex®, and nitromethane. This method offers a convenient and sensitive method of detection of trace nitroaromatic explosive residue.

Luminescent oligo(tetraphenyl)silole nanoparticles as chemical sensors for aqueous TNT

Colloidal oligo(tetraphenyl)silole nanoparticles in THF/H2O suspensions show increased luminescence and offer a method to detect TNT in an aqueous environment.

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 (λem ≈ 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 (λem = 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.