Detection Of Explosive Materials Research Articles

Artificial intelligence technologies utilization for detecting explosive materials

Explosive material detection considers the identification and classification of explosive materials using techniques from traditional sniffer dogs to cutting-edge sensing technology like thermal imaging, X-ray scanners, and chemical sensors. Explosive detection is applied in various locations, including airports, government buildings, and public areas, to prevent terrorist attacks and criminal actions that attempt to employ explosive devices. The effectiveness of these procedures is dependent on the detection materials, equipment, and environment, so new techniques are continuously explored to increase precision, sensitivity, and detection speed. Because explosive substances present a critical risk to infrastructure, security, and public safety, extensive analysis of existing detection methods is needed. This paper highlights key areas for further research and development in explosive materials detection by addressing identified limitations and challenges. Specifically, advancements in technology, interdisciplinary collaboration, and the integration of AI techniques offer significant opportunities for improving detection accuracy, reducing false positives, and ensuring safer environments for individuals and society.

Novel molecular laser-induced photoluminscence signature with hyperspectral imaging for instant and remote detection of trace explosive materials

Instant detection of explosive material is highly appreciated for counterterrorism activity and homeland security. Nitro group (high energy rich bond) is responsible for explosive characteristics. Nitro group includes intense competition between two highly electronegative atoms. Nitro group is frequently encountered in all explosive materials. This function group includes delocalized π bond; that could secure intense photoluminescence (fluorescence and phosphorescence) signature. In this study, the main classes of explosive materials including nitro-compounds (i.e. TNT), nitramines (i.e. RDX), and nitric esters (i.e. PETN) were stimulated with green laser source of 532 nm and 5 mW power. The photoluminescence signature of each tested material was captured via hyperspectral camera. The tested explosives demonstrated characteristic fluorescence signature at 571, 587, and 613 nm for RDX, PETN, and TNT respectively. Furthermore, TNT demonstrated characteristic phosphorescence signature at 975 nm. The customized laser induced photoluminescence technique offered facile detection of trace explosive material via clustering approach based on K-m clustering (k = 8); this technique was able to detect RDX, PETN and TNT traces on the finger nail via processed hyperspectral images at 581 nm, 797 nm and 953 nm, respectively. This study shaded the light on novel customized photoluminescence technique for facile detection and identification of trace explosive materials.

Detection of explosive materials in dual-energy X-Ray security systems

Due to the increasing security needs, X-ray devices have started to be used more and more in security systems. Dual-energy X-ray devices are preferred to conventional ones since they enable Effective Atomic Number (Zeff) estimation that cannot be provided by traditional devices, which use density-based segmentation. In this paper, pure material samples are used to obtain system characteristics. Linear mass attenuation coefficients (μ) of the materials can be calculated by using two leveled images, and these coefficients provide information about the Zeff of substances. After that, they can be classified as organic and inorganic via the effective atomic number method and explicitly identified. As well as this, organic explosives can be detected thanks to this simple and effective approach.

The Effect of Auxiliary Nitrogenated Linkers on the Design of New Cadmium-Based Coordination Polymers as Sensors for the Detection of Explosive Materials.

Three new cadmium-based coordination polymers, denoted [Cd(hfipbb)(4,4'-bipy)] (CdPF-1), [Cd(hfipbb)(2,2'-bipy)] (CdPF-2), and [Cd(hfipbb)(1,10-phen)] (CdPF-3), have been hydrothermally synthesized by using the well-known V-shaped organic linker 4,4'-(hexafluoroisopropylidene)bis(benzoic acid) (H2 hfipbb), together with different nitrogenated auxiliary linkers. Considering the d10 configuration of the transition metal selected, the luminescent properties for these CdPF-n materials were explored, finding that materials CdPF-2 and CdPF-3 act as excellent sensors in the detection of explosive nitro aromatic compounds. The photoluminescence properties of CdPF-2 and CdPF-3 revealed that significant and sensitive fluorescence quenching was observed toward NP (nitrophenol) for CdPF-2 and PA (picric acid) for CdPF-3 in MeOH suspensions.

Remote mid IR Photoacoustic Spectroscopy for the detection of explosive materials

Standoff photoacoustic detection of explosives using quantum cascade laser has been studied. The laser beam has been focused on to the target molecules adsorbed on metallic surfaces. A 25 kHz microphone, a resonator cavity in form of a cylinder, and a parabolic acoustic reflector have been used to demonstrate the method. The experimental results have been compared with the theoretical calculations in three different experimental conditions. The photoacoustic signals have been found to decrease with increase in the standoff range. The sensitivity of 2.0 µg/cm2 has been achieved at ~4.0 m.

Flexible porphyrin doped polymer optical fibers for rapid and remote detection of trace DNT vapor.

With the rapid growth of anti-terrorist activities worldwide, it becomes an emerging requirement to rapidly and accurately detect hidden explosive threats. However, the safety issue during the explosive material detection, e.g. unexpected explosion, is still an insurmountable challenge. In this study, we design and mass-produce a novel kind of flexible 5,10,15,20-tetrakis(4-aminophenyl)porphyrin doped polymer optical fiber (PPOF) for rapid and accurate detection of trace 2,4-dinitrotoluene (DNT) vapor based on the DNT induced florescence quenching mechanism. The influence of doping concentration, bending, and temperature on the sensing performance is investigated. PPOF shows immunity to bending, enabling it to work in a harsh environment. It is experimentally demonstrated that the limit of detection and response time of the proposed PPOF could reach around 120 ppb and 3 minutes, respectively, which make it much better than other techniques. Owning to its inherent advantages including low-cost, remote-control capability, and compatibility with optical communication networking, PPOF can be constructed the quasi-distributed sensing networking of explosive matters in the future, providing a new strategy for anti-terrorism.

Detection of explosive materials and their precursors through translucent commercial bottles using spatially offset Raman spectroscopy using excitation wavelength in visible range

The detection and analysis of hazardous materials through opaque barriers is important for law enforcement agencies. Conventional Raman spectroscopy provides fingerprint signatures of materials but lacks the ability to detect materials through opaque containers. Spatially offset Raman spectroscopy (SORS) overcomes the limitation of conventional Raman spectroscopy and allows the detection of materials through most commercial bottles and packaging materials. Moreover, SORS has the potential to detect hazardous materials through colored glass bottles, high-density polyethylene (HDPE) bottles, Teflon layers, etc., which is required in the screening of commercial packaging at airports and other vital facilities. SORS was investigated in the visible range with a 532-nm excitation source for the detection of urea and sodium nitrate through commercial packaging, i.e., a white HDPE bottle with a thickness of 1 mm. The effects of the spatial offset and integration time on the Raman spectra of the contents and container were evaluated. The trend of the change in the relative contributions from the contents and container was studied by varying the offset and integration time. P-nitrobenzoic acid was detected through the colored bottles in the study of reduction of fluorescence in the SORS effect.

Surface modified colloidal silica nanoparticles: Novel aspect for complete identification of explosive materials

Terrorism by means of explosives has become a crucial threat. Nanoparticles with distinctive properties can offer novel aspects for instant detection of explosive materials. Common explosives are organic compounds that contain nitro group (NO2) along with carbon and hydrogen elements. This study demonstrates complete identification of nitramine explosives (RDX & HMX) using colloidal silica nanoparticles. Sustainable fabrication of colloidal silica was conducted via hydrothermal processing technique. Explosive identification involves a digestion of the tested material using strong acid. The digestion process results in the development of nitro group and corresponding formaldehyde segment. The identification of the nitro group was performed using colloidal silica nanoparticles functionalized with secondary amine to develop a characteristic dark blue colour. Simultaneous identification of formaldehyde segment was performed using colloidal silica functionalized with aromatic phenol to develop a red colour. This robust explosive detection technology can find wide applications on site where instant identification to assess potential threat is a crucial demand. Thanks to hydrothermal processing, sustainable fabrication and surface modification of colloidal silica particles can be obtained.

Hydrogel Based-Electrochemical Gas Sensor for Explosive Material Detection

In Thailand, most of the bomb devices produced by the terrorists use trinitrotoluene (TNT) as the main explosive material. Detecting TNT and preventing detonation could save many civilians. Due to its low vapor pressure, TNT requires an extremely high sensitivity method for detection. In this paper, we propose an application of the polyacrylamide gel as an electrochemical gas sensor for explosive material detection. Cyclic voltammetry signals were collected from samples, including TNT, pentaerythritol tetranitrate (PETN), and non-explosive vapors. It was found that a time-derivative calculation of the signal was unique to each chemical, rather than the signal itself, demonstrating utility for the detection of explosive material. This approach for making a gel-based sensor and the data analysis looks promising and requires further validation.

Impedimetric Sensors: Principles, Applications and Recent Trends

This work figures the conceptual background of impedimetric measurements. Impedance measurement is a convenient approach for exploring the change in electrical behavior of diverse materials. An overview of in practice impedance analysis on CHI660D electrochemical work station is presented. Detection of microorganism causing foodborne diseases using IDE and other methods, toxic metal ion quantification, environment pollutant monitoring are described applications in this work. This work also reviewed the noticeable development in impedance measurement devices based on AD5933 such as bio-impedance measurement and explosive material detection. Biological signals are detected by transducing them into electrical analogy, detection of which is not a big issue. The main challenges are to convert biological signal into electrical information. Electrochemical sensors present captivating techniques to determine the content of sample under test. Electrochemical sensing platforms come up with an appealing methodology to interpret the concentration of biological sample as these sensors directly translate biological information to an electronic one. Huge amount of sensing platforms and corresponding devices has been developed. EIS is a rapid and easily computerized technique used to characterize biomolecules, inorganic materials, having a wide range of applications. The measured impedance spectra are generally fitted to an analogous electrical circuit model which constitutes an electrical documentation of the SUT by disclosing its behavior and properties. Quick, highly selective/specific and sensitive techniques to quantify biological and biochemical molecules and other target species are of great importance in biomedical and biotechnological application. Recent developments trends for handy, portable, fast and precise impedance analyzer is discussed. AD5933 evolution kit is reviewed.

Fiber optic coupled quantum cascade infrared laser system for detection of explosive materials on surfaces

The design and assembly of a unique infrared (IR) optical-fiber combined quantum cascade laser (QCL) system is described. This system integrates the output from four individual QCL modules, using infrared optical fibers, into a single output aperture to provide continuous spectral scanning from 6.02 to 11.17 µm. Spectra were collected on a diffuse gold reference as well as multiple concentrations of the explosive 1,3,5-Trinitro-1,3,5-triazinane (RDX) which were inkjet printed on aluminum substrates. The collected RDX spectra were compared to RDX spectra collected using a conventional Fourier-transform infrared spectrometer (FTIR). The results show good agreement between the spectra collected using the fiber-combined QCL system and the standard FTIR.These results demonstrate that the use of infrared optical fibers to combine multiple QCL modules is a viable approach to developing IR laser sources for use in fieldable devices capable of standoff detection of explosives.

Identification and classification of explosives using semi-supervised learning and laser-induced breakdown spectroscopy

Public places are often under threat from explosion events, which pose health and safety risks to the public. Therefore, the detection of explosive materials has become an important concern in the fields of antiterrorism and security. Laser-induced breakdown spectroscopy (LIBS) has been demonstrated to be useful in identifying explosives but has limitations. This study focuses on using semi-supervised learning combined with LIBS for explosive identification. Labeled data were utilized for the construction of a semi-supervised model for distinguishing explosive clusters and improving the accuracy of the K-nearest neighbor algorithm. The method requires only minimal prior information, and the time for obtaining a large amount of labeled data can be saved. The results of our investigation demonstrated that semi-supervised learning with LIBS can be used to discriminate explosives from interfering substances (plastics) containing similar components. The algorithm exhibits good robustness and practicability.

Real-time stand-off detection of improvised explosive materials using time-gated UV–Raman spectroscopy

A transportable, trolley-mounted stand-off explosive material detection system based on the time-gated Raman spectroscopy was developed and tested in our laboratory. This system is capable of identifying the explosives and improvised explosive materials located up to a distance of 30 m. A frequency tripled Nd:YAG, nanosecond pulsed laser (355 nm, 6 ns) operated at 10 Hz was used as an excitation source to induce Raman spectra of explosive materials under investigation. A reflected type 200 mm aperture telescope designed using Zemax optical design software was used to collect the backscattered Raman signals. Raman signals were recorded using the gated intensified charge coupled device (ICCD) spectrograph. A LabVIEW-based data acquisition and analysis software for real-time identification of materials was developed and used. It gives audio as well as text alarm to the operator about threat identification.

Evaluation of selected SERS substrates for trace detection of explosive materials using portable Raman systems

Raman spectroscopy has become an essential analytical technique for field detection and identification of illicit or dangerous materials such as explosives, but its main drawback is low signal intensity. This problem can be circumvented by using surface enhanced Raman spectroscopy (SERS), in which scattering signals increase significantly for analytes adsorbed onto or near nanostructured surfaces of the plasmonic materials. However, despite numerous studies, SERS has still not been widely used in real-world applications. The main goal of the studies describe herein was to investigate the possibility of detection of trace amounts of selected explosive materials on various commercial and non-commercial SERS substrates using portable Raman instruments. Our studies have shown that while portable systems suitable for SERS measurement of trace amounts of explosives are readily available, the problem remains in the selection of reliable and reproducible SERS substrates. Among five investigated SERS substrates only two, Klarite 312 and GaN-pillars allowed for trace analysis of all studied explosive materials. In both cases, detected concentrations of explosives ranged from single to hundreds of μg/cm2 depending on the explosive material and the Raman spectrometer used. Based on our findings, it could be concluded that the best SERS substrates for trace analysis of explosives are substrates with hot spots densely and evenly distributed over a whole active area of SERS substrate.

Simulation of an efficient particle extraction for the detection of explosive materials

This work analyzes the fluidic dynamics of the particle extraction function of a nozzle used for the detection of explosives in simulation studies. The nozzle shape with inlet and outlet gas connection is able to extract particles generated by the laser drilling process. Drilling dependent parameters such as the diameter of the generated particles, initial particle velocity, and drilling hole depth are investigated in terms of the residence time of these particles within the extraction nozzle. Besides these, the performance of an applied inlet and outlet gas flow is examined.

New Ni-Anthracene Complex for Selective and Sensitive Detection of 2,4,6-Trinitrophenol

Selective and sensitive detection of explosive materials through a simple approach is an attractive area of research having implications on public safety and homeland security. Considering this implication in mind, a new Ni-anthracene complex was designed and synthesized and has been demonstrated as an efficient fluorescence chemosensor for the selective and sensitive detection of 2,4,6-trinitrophenol. Firstly, a fluorescent anthracene ligand (A) was synthesized by treating anthracene-9-carboxaldehyde with 1,3-diaminopropane in presence of a weak acid. To achieve superior selectivity and great quenching efficiency for 2,4,6-trinitrophenol (TNP), a Ni complex, namely, [Ni(μ2-L)(NO3)] (B), was synthesized via the reaction of A with Ni(NO3)2·6H2O. Complex B showed strong emission peak (λmax) at 412 nm and exhibited high selectivity towards TNP among other nitroaromatics and anions. 100 equivalents of TNP made 95% fluorescence quenching of B and its detection limit for TNP was calculated as 2.8 μM.

Proposal for a Monolithic Broadband Terahertz Quantum Cascade Laser Array Tailored to Detection of Explosive Materials

Proposal for a Monolithic Broadband Terahertz Quantum Cascade Laser Array Tailored to Detection of Explosive Materials

Testing Method for On‐Site Measurement of Explosive Materials Contaminated on Travel Luggage Bag and Backpack Using Ion Mobility Spectrometry

Testing method for the on‐site detection of explosive materials contaminated on the travel luggage bag (TLB) and backpack (BP) surfaces was established using ion mobility spectrometry (IMS) and smear matrix. Trinitrotoluene and 1,3,5‐trinitro‐1,3,5‐triazacyclohexane were used as model explosive materials. Two sampling methods of rolling (with a metal roller) and handrubbing were used, and stainless steel mesh was used as the smear matrix for collection of explosive material. Testing parts of the TLB and BP were selected in consideration of contaminant accumulation, physical contact, and sample collection. Explosive materials deposited on polytetrafluoroethylene (PTFE) sheet were transferred to the testing part, the explosive materials existing on the testing part were collected using the smear matrix, and then the collected explosive materials were analyzed using IMS. High signal‐to‐noise ratio over 10 was applied for the determination of the minimum initial explosive concentration (Cmin_PTFE) to detect in IMS. The hand‐rubbing method was much more efficient than the rolling method. The Cmin_PTFE values were different according to the testing parts. The Cmin_PTFE values of the TLB were higher than those of the BP. The experimental results were explained by difference in surface morphology of the testing areas. The testing method can be helpful to select the sampling parts and to collect the explosive materials for on‐site security checks.

Novel laser induced photoacoustic spectroscopy for instantaneous trace detection of explosive materials

Laser photoacoustic spectroscopy (LPAS) is an attractive technology in terms of simplicity, ruggedness, and overall sensitivity; it detects the time dependent heat generated (thermo-elastic effect) in the target via interaction with pulsed optical radiation. This study reports on novel LPAS technique that offers instant and standoff detection capabilities of trace explosives. Over the current study, light is generated using pulsed Q-switched Nd:YAG laser; the generated photoacoustic response in stimulated explosive material offers signature values that depend on the optical, thermal, and acoustical properties. The generated acoustic waves were captured using piezoelectric transducer as well as novel customized optical sensor with remotely laser interferometer probe. A digital signal processing algorithm was employed to identify explosive material signatures via calculation of characteristic optical properties (absorption coefficient), sound velocity, and frequency response of the generated photoacoustic signal. Customized LPAS technique was employed for instantaneous trace detection of three main different high explosive materials including TNT, RDX, and HMX. The main outcome of this study is that the novel customized optical sensor signals were validated with traditional piezoelectric transducer. Furthermore, the customized optical sensor offered standoff detection capabilities (10cm), fast response, high sensitivity, and enhanced signal to noise ratio. This manuscript shaded the light on the instant detection of trace explosive materials from significant standoffs using novel customized LPAS technique.

Development of a Miniature Mass Spectrometer and an Automated Detector for Sampling Explosive Materials.

The development of a robust ionization source using the counter-flow APCI, miniature mass spectrometer, and an automated sampling system for detecting explosives are described. These development efforts using mass spectrometry were made in order to improve the efficiencies of on-site detection in areas such as security, environmental, and industrial applications. A development team, including the author, has struggled for nearly 20 years to enhance the robustness and reduce the size of mass spectrometers to meet the requirements needed for on-site applications. This article focuses on the recent results related to the detection of explosive materials where automated particle sampling using a cyclone concentrator permitted the inspection time to be successfully reduced to 3 s.