Abstract
1,3,5-trinitroperhydro-1,3,5-triazine (RDX), octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), and pentaerythritol tetranitrate (PETN), the major components in plastic explosives, pose a significant threat to public safety. A quick, sensitive, and low-cost detection method for these non-volatile explosives is eagerly demanded. Here we present a fluo-spot approach, which can be employed for in situ detection of trace amount of explosives. The sensor molecule is a charge-transfer fluorophore, DCM, which is strongly fluorescent in its pristine state, but non-fluorescent after the quick reaction with NO2· (or NO2+) generated from the UV photolysis of RDX, HMX (or PETN). When fabricated within silica gel TLC plate, the fluo-spot sensor features high sensitivity owing to the large surface area and porous structure of the substrate. The sensor reaction mechanism was verified by various experimental characterizations, including chromatography, UV-Vis absorption and fluorescence spectroscopy, MS and 1H NMR spectrometry. The fluo-spot also demonstrated high selectivity towards RDX, HMX and PETN, as no significant fluorescence quenching was observed for other chemical compounds including common nitro-aromatic explosives and inorganic oxidative compounds. The DCM sensor can also be used as an economical spray kit to directly spot the explosives by naked eyes, implying great potential for quick, low-cost trace explosives detection.
Highlights
Developing efficient detection methods for trace explosives has drawn intense attention due to increasing concerns about homeland security and public safety1
UV irradiation of the DCM solution containing RDX resulted in gradual decrease in fluorescence intensity of DCM, and complete fluorescence quenching was observed after 180 s of irradiation (Fig. 2a,c)
This fluorescence quenching indicates the destruction of the charge transfer structure of DCM by reacting with the NO2· radical produced from photolysis of RDX
Summary
Developing efficient detection methods for trace explosives has drawn intense attention due to increasing concerns about homeland security and public safety. It was found that RDX or PETN undergoes photolysis to generate the reactive intermediate species, NO2· radical or NO2+ cation, respectively, under the irradiation of UV light13 Both NO2· and NO2+ can be captured and detected by fluorescence sensor molecules. In order to optimize the sensor’s solid detection performance, a capillary is used to quantitatively load trace amount of DCM dye onto a thin-layer chromatography (TLC) silica gel plate to create a fluo-spot sensor. In this system, the DCM dye is dispersed into the porous silica substrate, which features a large surface area to ensure the efficient solid phase reaction with the target species. To move the sensor into real application, unbiased detection of RDX was achieved on various common surfaces by using a solution spray technique
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