The storage and use of explosives is regulated at the state and federal level, with a particular focus on physical security and rigorous accounting of the explosive inventory. For those working with ...explosives for the training and testing of explosive‐detecting canines, cross‐contamination is an important concern. Hence, explosives intended for use with canine teams must be placed into secondary storage containers that are new, clean, and airtight. A variety of containers meet these requirements and include screw‐top glass jars (e.g., mason jars). However, an additional need from the explosive‐detecting canine community is secondary containers that can also be used as training aids whereby the volatiles emitted by explosives are emitted in a predictable and stable manner. Currently, a generally accepted method for the storage of explosives and controlled emission of explosive vapor for canine detection does not exist. Ideally, such containers should allow odor to escape from the training aid but block external contaminates such as particulates or other volatiles. One method in use places the explosive inside a permeable cotton bag when in use for training and then stores the cotton bag inside an impermeable nylon bag for long‐term storage. This paper describes the testing of an odor permeable membrane device (OPMD) as a new way to store and deploy training aids. We measured the evaporation rate and flux of various liquid explosives and volatile compounds that have been identified in the headspace of actual explosives. OPMDs were used in addition to traditional storage containers to monitor the contamination and degradation of 14 explosives used as canine training aids. Explosives were stored individually using traditional storage bags or inside an OPMD at two locations, one of which actively used the training aids. Samples from each storage type at both locations were collected at 0, 3, 6, and 9 months and analyzed using Fourier Transform Infrared (FTIR) Spectroscopy and Gas Chromatography–Mass Spectrometry (GC–MS) with Solid‐Phase Microextraction (SPME). FTIR analyses showed no signs of degradation. GC–MS identified cross‐contamination from ethylene glycol dinitrate (EGDN) and/or 2,3‐dimethyl‐2,3‐dinitrobutane (DMNB) across almost all samples regardless of storage condition. The contamination was found to be higher among training aids that were stored in traditional ways and that were in active use by canine teams.
Military-grade explosives such as 2,4,6-trinitroluene (TNT) are still a major worldwide concern in terms of terror threat and environmental impact. The most common methods currently employed for the ...detection of explosives involve colorimetric tests, which are known to be rapid and portable; however, they often display false positives and lack sensitivity. Other methods used include ion mobility mass spectrometry, gas chromatography-mass spectrometry (GC-MS), and liquid chromatography-mass spectrometry (LC-MS), which despite producing more reliable results often require large, expensive instrumentation and specially trained staff. Here we demonstrate an alternative approach that utilizes the formation of a colored Janowsky complex with nitroaromatic explosives through reaction of the enolate ion of 3-mercapto-2-butanone. The colored complex is formed rapidly and can then be detected sensitively using surface-enhanced Raman scattering (SERS). We demonstrate that SERS can be used as a quick, sensitive, and selective technique for the detection of 2,4,6-trinitrotoluene (TNT), hexanitrostillbene (HNS), and 2,4,6-trinitrophenylmethylnitramine (tetryl) with a detection limit of 6.81 ng mL–1 achieved for TNT, 17.2 ng mL–1 for tetryl, and 135.1 ng mL–1 for HNS. This method of detection also requires minimal sample preparation, can be done in a solution-based format, and utilizes the same precursor reagents for complex formation with each of the explosives which can then be identified due to the specificity of the unique SERS response obtained. We demonstrate the ability to simultaneously identify three explosive compounds within a total analysis time of 10 min. This method of detection shows promise for the development of rapid and portable SERS-based assays which can be utilized in the field in order to achieve reliable and quantitative detection.
With the ever-increasing threat of improvised explosive devices (IEDs) and homemade explosives (HME) both domestically and abroad, detection of explosives and explosive related materials is an area ...of urgent importance for preventing terrorist activities around the globe. Canines are a common biological detector used in explosive detection due to their enhanced olfactory abilities, high mobility, efficient standoff sampling, and optimal identification of vapor sources. While other sensors based on different principles have emerged, an important concept for the rapid field detection of explosives is understanding key volatile organic compounds (VOCs) associated with these materials. Explosive detection technology needs to be on par with a large number of threats including an array of explosive materials as well as novel chemicals used in the manufacture of IEDs. Within this much needed area of research for law enforcement and homeland security applications, several studies have sought to understand the explosive odor profile from a range of materials. This review aims to provide a foundational overview of these studies to provide a summary of instrumental analysis to date on the various types of explosive odor profiles evaluated focusing on the experimental approaches and laboratory techniques utilized in the chemical characterization of explosive vapors and mixtures. By expanding upon these concepts, a greater understanding of the explosive vapor signature can be achieved, providing for enhanced chemical and biological sensing of explosive threats as well as expanding upon existing laboratory-based models for continued sensor development.
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•Detection of explosives and their related materials is an area of urgent importance.•Understanding of volatile organic compounds (VOCs) is key to rapid field detection of explosives.•Enhanced olfactory abilities and high mobility makes canines an excellent tool in biological detection of explosives.•Explosive detection technology must stay up to date with current and expanding threats.•Experimental techniques provide understanding of explosive vapor odor signatures for enhanced sensor development.
This
critical review
is focused on examples reported from 1947 to 2010 related to the design of chromo-fluorogenic chemosensors and reagents for explosives (141 references).
This review is focused on ...examples reported from 1947 to 2010 related to the design of chromo-fluorogenic chemosensors and reagents for explosives.
DNT (2,4-dinitrotoluene), a volatile impurity in military-grade 2,4,6-trinitrotoluene (TNT)-based explosives, is a potential tracer for the detection of buried landmines and other explosive devices. ...We have previously described an
bioreporter strain engineered to detect traces of DNT and have demonstrated that the
gene promoter, the sensing element of this bioreporter, is induced not by DNT but by at least one of its transformation products. In the present study, we have characterized the initial stages of DNT biotransformation in
, have identified the key metabolic products in this reductive pathway, and demonstrate that the main DNT metabolite that induces
is 2,4,5-trihydroxytoluene. We further show that
cannot utilize DNT as a sole carbon or nitrogen source and propose that this compound is metabolized in order to neutralize its toxicity to the cells.
The information provided in this article sheds new light both on the microbial biodegradability of nitroaromatic compounds and on the metabolic capabilities of
By doing so, it also clarifies the pathway leading to the previously unexplained induction of the
gene by 2,4-dinitrotoluene, an impurity that accompanies 2,4,6-trinitrotoluene (TNT)-based explosives. Our improved understanding of these processes will serve to molecularly enhance the performance of a previously described microbial bioreporter of buried landmines and other explosive devices, in which the
gene promoter serves as the sensing element.
The detection of ultralow or nonvolatile target analytes remains a significant challenge for artificial olfactory systems even after decades of development, which severely limits their widespread ...application. To overcome this challenge, an artificial olfactory system based on a colorimetric hydrogel array is constructed for the first time as a universal representative. As an effective extension of conventional artificial olfactory systems that integrates the merits of its predecessors, the proposed system accurately mimics olfactory mucosa and specific odorant binding proteins using hydrogels endowed with specific colorimetric reagents for the detection of hypochlorite, chlorate, perchlorate, urea, and nitrate. Therefore, the proposed system is capable of detecting and discriminating between these five airborne improvised explosive microparticulates with a detection limit as low as 39.4 pg. Additionally, the system demonstrates good reusability over ten cycles, rapid response time of ≈0.2 s, and excellent discrimination properties, despite significant variation. This proof‐of‐concept study on colorimetric artificial olfactory systems yields a novel strategy for the direct and discriminative detection of nonvolatile airborne microparticulates.
A colorimetric artificial olfactory system with excellent discrimination capabilities, rapid response time, and low detection limit is proposed for detecting airborne improvised explosive microparticulates. The proposed system integrates the merits of previous artificial olfactory systems and overcomes common drawbacks, which can not only resolve the challenges of improvised explosive detection, but also make the detection of nonvolatile target analytes possible.
This paper presents a systematic study of structure and mechanical behavior of Ti/Fe explosive-bonded interfaces. The transient fluid-like behavior at the bonding zone is simulated using Smoothed ...Particle Hydrodynamic (SPH) numerical method. The interface is featured by a wave structure, resulted from heavy plastic deformation during the explosive welding. Melted zone resulted from the trapped jetting is surrounded by strongly deformed bulk materials. Fe2Ti intermetallic compounds with a mixture of FeTi+Fe phases are observed in the melted zone. A reaction layer (~700nm) consisted of nano-sized FeTi grains is formed at Ti/Fe material boundary. Nanoindentation tests and fracture observation confirm the brittle nature of Fe-Ti intermetallics formed in the explosive-bonded joint. Extremely temperature accumulated near the interface leads to recovery and recrystallization in deformed grains, which can accommodate relatively large strain near the interface.
Swabs taken from the surface of a suspicious object are a standard method of identifying a concealed explosive device in security-conscious locations like airports. In this paper we demonstrate a ...sensitive method to collect and detect trace explosive residues from improvised explosive devices using swabs and an optical sensor element. Swabs coated with a commercial fluoropolymer are used to collect material and are subsequently heated to thermally desorb the explosives, causing the quenching of light emission from a thin film luminescent sensor. We report the sorption and desorption characteristics of swabs loaded with 2,4-DNT tested with Super Yellow fluorescent sensors in a laboratory setting, with detection that is up to three orders of magnitude more sensitive than standard colorimetric tests. The method was then applied in field tests with raw military-grade explosives TNT, PETN and RDX, on various objects containing the explosives, and post-blast craters. We show for the first time results using organic semiconductors to detect sub-milligram amounts of explosive sorbed onto a substrate from real explosives in the field, giving a promising new approach for IED detection.
Swabs taken from the surface of a suspicious object are a standard method of identifying a concealed explosive device in security-conscious locations like airports. Light-emitting polymer sensors can detect trace amounts
via
fluorescence quenching.
Explosive welding is one of the joining techniques which employs high energies derived from explosives to join materials with similar and dissimilar properties. In this paper, the weldability ...criteria which should be met to achieve good welds were calculated for aluminum–copper joints. Different morphologies for welding interface (straight, wavy and melted layer) were obtained with changing welding parameters. Results on the microstructure, micro-hardness and tensile-shear tests were reported. Tensile-shear test results indicate that shear bond strength increases with increasing explosive ratio. However, shear bond strength decreases when the explosive ratio exceeds R=2.2 due to the formation of brittle intermetallics at the interface. This knowledge may be utilized for establishment of a relation between microstructure and properties in the process of manufacturing.
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•Explosive welding process was described and reviewed.•Interface morphology of Al/Cu joints was successfully predicted by welding window.•Effects of explosive ratio on the welding interface were investigated.•Bond strength of different interfaces was evaluated using tensile shear test.•Wavy interface under high explosive ratio had the highest bonding shear strength.
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