•A novel fluorescent paper sensor was developed based on fluorescent nanoporous polymer.•The paper sensor is highly sensitive for visually detecting nitroaromatic explosives in solution, solid and ...vapor phases.•The paper sensor is recyclable.
Development of rapid, sensitive, and visual detection of nitroaromatic explosives is of great importance for homeland security and human safety. Herein, three novel fluorescent nanoporous polymers (FNPs), HPP-1–HPP-3, were first prepared by Heck reactions of octavinylsilsesquioxane with ethene derivatives containing bis-, tri-, or tetrakis- bromophenyl groups. Based on highly sensitive detection of explosives, including p-nitrotoluene (NT), 2,4-dinitrotoluene (DNT), 2,4,6-trinitrotoluene (TNT), 4-nitrophenol (NP), 2,4-dinitrophenol (DNP) and picric acid (PA), and high selectivity for detecting TNT and PA, by HPP-2 dispersion in ethanol, a fluorescent paper sensor was developed by a new fabrication process, i.e., vacuum filtrating of HPP-2 dispersion in ethanol, followed by washing and natural drying. The resultant paper sensor was found to be sensitive to explosives in the solution, solid and vapor phase with a rapid response time of < 10 s by visually observing the fluorescence quenching phenomenon. Moreover, this paper sensor is recyclable with desirable fluorescence resuming ratio, which is higher than 75% after 10 times recycle detection. This developed paper sensor is promisingly applied for rapid, on-site and visual sensing of explosive residuals. The remarkable fluorescence and reusability of this sensor could be expanded to other fluorescence detection of residuals.
Three new electron‐rich metal–organic frameworks (MOF‐1–MOF‐3) have been synthesized by employing ligands bearing aromatic tags. The key role of the chosen aromatic tags is to enhance the π‐electron ...density of the luminescent MOFs. Single‐crystal X‐ray structures have revealed that these MOFs form three‐dimensional porous networks with the aromatic tags projecting inwardly into the pores. These highly luminescent electron‐rich MOFs have been successfully utilized for the detection of explosive nitroaromatic compounds (NACs) on the basis of fluorescence quenching. Although all of the prepared MOFs can serve as sensors for NACs, MOF‐1 and MOF‐2 exhibit superior sensitivity towards 4‐nitrotoluene (4‐NT) and 2,4‐dinitrotoluene (DNT) compared to 2,4,6‐trinitrotoluene (TNT) and 1,3,5‐trinitrobenzene (TNB). MOF‐3, on the other hand, shows an order of sensitivity in accordance with the electron deficiencies of the substrates. To understand such anomalous behavior, we have thoroughly analyzed both the steady‐state and time‐resolved fluorescence quenching associated with these interactions. Determination of static Stern–Volmer constants (KS) as well as collisional constants (KC) has revealed that MOF‐1 and MOF‐2 have higher KS values with 4‐NT than with TNT, whereas for MOF‐3 the reverse order is observed. This apparently anomalous phenomenon was well corroborated by theoretical calculations. Moreover, recyclability and sensitivity studies have revealed that these MOFs can be reused several times and that their sensitivities towards TNT solution are at the parts per billion (ppb) level.
Competing size and electronic effects: Luminescent Zn‐MOFs can be prepared by employing π‐electron‐rich isophthalic acid derivatives bearing fluorescent tags. These MOFs can be used for sensing nitroaromatic explosives on the basis of fluorescence quenching (see graphic; 4‐NT=4‐nitrotoluene; TNT=trinitrotoluene). For the more porous MOFs, the fluorescence quenching is dictated by size selection. For MOFs in which the pores are blocked by pyrenyl tags, the fluorescence quenching thus occurs on the surface and conforms to the electronic properties of the analytes.
The usage of Unmanned Aerial Vehicles (UAV)-based Ground Penetrating Radar (GPR) systems has gained interest over the last years thanks to advantages over ground-based systems such as contactless ...inspection and capability to reach difficult-to-access areas. The former is of paramount importance concerning the detection of buried threats such as Improvised Explosive Devices (IEDs) and landmines. Current state-of-the-art UAV-based GPR systems are able to provide centimeter-level resolution thanks to the use of GPR-Synthetic Aperture Radar (SAR) processing techniques. One of the challenges to keep improving these systems is the scanning throughput, that is, the area that can be scanned in a given time. This contribution presents an array-based GPR-SAR system for subsurface imaging, aiming at maximizing the scanning throughput without jeopardizing the imaging capabilities of the system. First, the antenna array is mounted on a portable setup to evaluate its performance and imaging capabilities. Next, the antenna array is integrated into the UAV platform, and the UAV-based GPR-SAR system with the array is tested in realistic scenarios with different kinds of buried targets. Results show that the scanning throughput is significantly improved and, furthermore, the coherent combination of all transmitting-receiving channels of the array provides enhanced detection capabilities.
Explosives analysis has a significant practical application in the areas of national public security, anti-terrorism, stability maintenance, criminal investigation, national defense and military ...industry, and environmental protection. There may be some restrictions for conventional explosive detection and analytical techniques, such as excessive sample preparation complexity or specific security issues. However, laser-induced breakdown spectroscopy (LIBS) has several promising advantages, including easy sample pretreatment, trace substance identification, rapid analysis speed and standoff detection, and has been used in explosive analysis. This review summarizes the basic principles of LIBS and its development and application in the field of hazardous explosives in recent years. In more detail, it introduces the identification of inorganic and organic explosives under the interference of various substances, fingerprint identification of explosives, and standoff detection of explosives. It also includes using LIBS and laser-induced air shock from energetic materials technique to predict the potential performance of explosives (detonation velocity, the heat of combustion, detonation energy, detonation pressure, etc.). Finally, some future directions for LIBS are proposed. It will help readers to better understand the current research status of the LIBS technique in explosive analysis.
•The recent advances in laser-induced breakdown spectroscopy for explosive analysis is presented.•This section of the review includes the basic principles of LIBS, experimental conditions, and data processing methods.•This review introduces the identification and prediction of potential properties of explosives using LIBS techniques.
► We discuss a wide number of methods for detection of explosives. ► Spectroscopic, electrochemical and biochemical methods are discussed. ► An overview of nanomaterials and their effects is ...presented. ► Current commercial devices are compared and future trends were discussed.
The detection of explosives and explosive-related compounds has become a heightened priority in recent years for homeland security and counter-terrorism applications. There has been a huge increase in research within this area—through both the development of new, innovative detection approaches and the improvement of existing techniques. Developments for miniaturisation, portability, field-ruggedisation and improvements in stand-off distances, selectivity and sensitivity have been necessary to develop and improve techniques. This review provides a consolidation of information relating to recent advances in explosive detection techniques without being limited to one specific research area or explosive type. The focus of this review will be towards advances in the last 5 years, with the reader being referred to earlier reviews where appropriate.
Highly luminescent micrometre-sized fine particles of a Zn(II) metal-organic framework (MOF) of a new π-electron rich tricarboxylate dispersed in ethanol is demonstrated as a selective sensory ...material for the detection of nitroaromatic explosives via a fluorescence quenching mechanism.
This study describes the development of an analytical methodology based on the use of microchip electrophoresis (ME) devices integrated with capacitively coupled contactless conductivity detection ...(C4D) for the separation and detection of inorganic anions in post‐blast explosive residues. The best separation condition was achieved using a running buffer composed of 35 mmol/L lactic acid, 10 mmol/L histidine and 0.070 mmol/L cetyl(trimethyl ammonium) bromide. For C4D measurements, the highest sensitivity was obtained applying a 700 kHz sinusoidal wave with excitation voltage of 20 Vpp. The separation of Cl−, NO3−, NO2−, SO42−, ClO4− and ClO3− was performed within ca. 150 s with baseline resolution and efficiencies between 4.4 × 104 and 1.7 × 105 plates/m. The found limits of detection ranged between 2.5 and 9.5 μmol/L. Last, real samples of post‐blast explosive residues were analyzed on the ME‐C4D devices obtaining successfully the determination of Cl−, NO3− and SO42−. The achieved concentration values varied between 12.8–72.5 mg/L for Cl−, 1.7–293.1 mg/L for NO3− and 1.3–201.3 mg/L for SO42−. The data obtained using ME‐C4D devices were in good agreement with the concentrations found by ion chromatography. The approach reported herein has provided short analysis time, instrumental simplicity, good analytical performance and low cost. Furthermore, the ME‐C4D devices emerge as a powerful and portable analytical platform for on‐site analysis demonstrating to be a promising tool for the crime scene investigation.
Chemical Classification of Explosives Zapata, Félix; García-Ruiz, Carmen
Critical reviews in analytical chemistry,
2021, Volume:
51, Issue:
7
Journal Article
Peer reviewed
This work comprehensively reviews some fundamental concepts about explosives and their two commonly used classifications based on either their velocity of detonation or their application. These ...classifications are highly useful in the military/legal field, but completely useless for the chemical determination of explosives. Because of this reason, a classification of explosives based on their chemical composition is comprehensively revised, discussed and updated. This classification seeks to merge those dispersed chemical classifications of explosives found in literature into a unique general classification, which might be useful for every researcher dealing with the analytical chemical identification of explosives. In the knowledge of the chemical composition of explosives, the most adequate analytical techniques to determine them are finally discussed.
•Flight characteristics of a blast-driven ball bearing embedded in a rear detonated cylindrical explosive.•Novel experimental techniques to measure ball bearing velocities and blast impulse ...characteristics.•Differences in detonation pressure profile and momentum transfer efficiency caused by different length-to-diameter ratios of the explosive charge.•Plastic deformation of ball bearing from blast loading.
This paper presents insights into the flight characteristics of a ball bearing embedded in a rear detonated cylindrical charge, which represents an idealised piece of shrapnel from an improvised explosive device. A novel experimental technique was developed to quantify the loading from a blast-driven ball bearing. The impulse contributions from the blast pressure and the ball bearing impact were separately identifiable in the experimental data. Computational simulations, validated using experimental data, were used to elucidate additional detail about the momentum transfer and damage in the ball bearings during the blast event. The results show the critical influence of charge mass and aspect ratio on the development of the detonation pressure profile, its interaction with the embedded bearing, and the flight characteristics of the bearing. Length-to-diameter ratios below a critical value were more efficient in transferring momentum to the embedded bearings. These findings provide unique and detailed insights that will prove valuable to blast protection engineers considering the effects of embedded projectiles in improvised explosive devices.
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