Sensors For Detection Of Explosives Research Articles

Moisture‐resistant nitroaromatic explosive gas sensor based on hydrophilic pentiptycene polymer

AbstractThe detection of explosive materials, particularly nitroaromatic compounds such as 2,4,6‐trinitrotoluene (TNT), is critical for public safety and national security. Existing detection methods often require complex instrumentation, limiting their applicability for real‐time or in‐field use. Fluorescent sensors, which offer rapid and sensitive detection through fluorescence quenching, present a promising alternative. This study evaluates the performance of two pentiptycene‐based polymers, P‐1 and P‐2, in detecting explosive vapors, with a specific focus on their behavior under high‐humidity conditions. P‐2, modified with triethylene glycol groups, demonstrated significantly increased hydrophilicity compared to the commonly studied P‐1, as confirmed by contact angle measurements. Spectroscopic analysis revealed a blue shift in P‐2's UV–Vis absorption and photoluminescence spectra, indicating electronic property changes due to structural modifications. The enhanced hydrophilicity of P‐2 enabled it to maintain stable sensing performance under moist conditions, showing less than a 10% reduction in sensitivity, compared to the 20% decrease observed in P‐1. This superior moisture resistance suggests that P‐2 is a more robust and practical sensor for explosive detection in environments with variable humidity levels.

Advanced functional rGO@MoS2@PEDOT: PSS multicomponent-based nanocomposite films for rapid and ultra-sensitive TNT detection

Ultra-sensitive and highly selective detectors are attracting increasing attention to combat any undesired terrorist activities. High sensitivity and selectivity are the two major concerns for the development of the sensor for explosive detection. Herein, 2,4,6 TNT explosive sensor based on multicomponent nanocomposite film (Mc-NFs) is fabricated through an interface modulation technique. The Mc-NFs, porphyrin functionalized rGO@MoS2 @PEDOT: PSS (TPP-rGO@MoS2 @PEDOT: PSS) films, exhibit excellent selectivity and ultra-sensitivity towards TNT vapor at room temperature with outstanding sensing response (246% for 1.5 ppb), a rapid response time (3.5 s). The obtained results reveal the synergistic actions of the individual sensor components, where the rich active sites of MoS2 are playing a major role in high sensing response, π-π interactions between TPP-rGO and TNT lead to rapid adsorption/desorption of TNT vapors, and PEDOT: PSS assures the homogenous dispersion of the components in the sensor film. Further, the film exhibits excellent selectivity towards highly oxidizing TNT vapors due to strong N-type nature of the film along with the functionalization of rGO with porphyrin. The sensor has also been investigated for different concentrations of TNT vapors in the concentration range of 1.5–47ppb, showing an average rapid response time of 2 s, and recovery time of 42.5 s. The sensor has a high sensitivity of 4.09% /ppb, remarkable linearity (R-value > 0.976), good reproducibility and repeatability, low limit of detection (0.1 ppb), and good sensing stability. The prepared TPP-rGO-10%@MoS2-5%@PEDOT: PSS film has the potential to be used as an ultra-sensitive TNT detector in handheld devices.

BODIPY-based fluorescent sensors for detection of explosives

The detecting and screening of explosives has become a global consideration in dealing with potential terrorism threats and the misuse of high explosives. Several detection techniques have been developed, but their disadvantages include the requirement of expensive equipment, complicated pre-treatment, and prolonged testing. So far, fluorescence-based sensors have been of great interest as they overcome the limitations of other techniques. BODIPY, which is a fluorophore, shows excellent fluorescence features, and it can be used as a sensor material for explosives detection. However, to date, BODIPY-based explosive sensors have not been explored in detail. This work reviews the recent developments on explosive sensors based on BODIPY and its analogs.

Gold nanoclusters-engineered dual-emitting nanofibrous film for fluorescent discrimination and visual sensing of explosives

Development of reliable sensors for explosive detection is important to reduce explosion-related safety risks and mitigate widespread environmental concerns. However, it remains highly challenging to achieve on-site detection of multiple analytes in a simple yet efficient way. Herein, a flexible electrospun film-based sensing platform by engineering with dual-emitting gold nanoclusters (AuNCs) has been fabricated for the simultaneous fluorescent detection of two representative explosives, hexanitrohexaazaisowurtzitane (CL-20) and trinitrotoluene (TNT). Particularly, two types of AuNCs with different emission colors (green and red) and surface chemistry are designed, which can specifically respond to trace amounts of two explosives separately. While the presence of CL-20 can remarkably enhance the green emission of l-arginine/6-aza-2-thiothymine-protected AuNCs, the presence of TNT can efficiently quench the red emission of glutathione-protected AuNCs. Consequently, ratiometric fluorescent sensing of CL-20 and TNT can be achieved with these dual-emitting AuNCs (G/R-AuNCs), which exhibits a detection limit down to 0.55 and 2.38 µM, respectively. The distinct “turn on” and “turn off” response patterns of G/R-AuNCs towards two explosives could be harnessed to construct fluorescent “BUF” and “NOT” logic gates. Moreover, the present AuNCs-based explosive sensors were deposited into flexible electrospun nanofibrous film for visual and quantitative detection of CL-20 and TNT, which exhibit good mechanical property and promising sensing performance. This work provides a new approach to design explosive sensing platform by coupling the attractive features of fluorescent AuNCs to the electrospun nanofibrous film, which holds great potential for further practical applications.

A compact optical sensor for explosive detection based on NIR luminescent quantum dots

Detection of explosive traces in the vapor phase is of primary importance for safety and security in several environments. Different detection methods with high sensitivity are available in the market, but they are typically expensive and require specialized personnel to be operated. Here, we propose a compact, low-cost sensor for explosive detection based on the photoluminescence (PL) quenching of solid-state PbS quantum dot solids cast from the solution phase on a silicon substrate. We demonstrate the sensor capability to detect nitrobenzene vapor at a concentration as low as 445 ppb in air at room temperature, overcoming the performance of other state-of-the-art quantum dot-based PL sensors for nitroaromatic compounds. Moreover, the proposed system can be realized with off-the-shelf electronics and does not need any additional laboratory equipment to be operated, thus paving the way for its deployment in distributed sensor networks.

Free-standing, thin-film sensors for the trace detection of explosives

In a world focused on the development of cybersecurity, many densely populated areas and transportation hubs are still susceptible to terrorist attacks via improvised explosive devices (IEDs). These devices frequently employ a combination of peroxide based explosives as well as nitramines, nitrates, and nitroaromatics. Detection of these explosives can be challenging due to varying chemical composition and the extremely low vapor pressures exhibited by some explosive compounds. No electronic trace detection system currently exists that is capable of continuously monitoring both peroxide based explosives and certain nitrogen based explosives, or their precursors, in the vapor phase. Recently, we developed a thermodynamic sensor that can detect a multitude of explosives in the vapor phase at the parts-per-trillion (ppt) level. The sensors rely on the catalytic decomposition of the explosive and specific oxidation–reduction reactions between the energetic molecule and metal oxide catalyst; i.e. the heat effects associated with catalytic decomposition and redox reactions between the decomposition products and catalyst are measured. Improved sensor response and selectivity were achieved by fabricating free-standing, ultrathin film (1 µm thick) microheater sensors for this purpose. The fabrication method used here relies on the interdiffusion mechanics between a copper (Cu) adhesion layer and the palladium (Pd) microheater sensor. A detailed description of the fabrication process to produce a free-standing 1 µm thick sensor is presented.

Selectivity enhancement of MIP-composite sensor for explosive detection using DNT-dengue virus template: A co-imprinting approach

Our current efforts are directed towards improving the selectivity of MIP composite sensors for detection of explosives. It is generally assumed that MIP selectivity depends mainly on compatibility between the analyte and polymer being used. Accordingly, less research has concentrated on applying imprinting techniques to modify the polymeric material. Where applied, imprinting has traditionally been carried out with one or two small target molecules simply mixed with or loaded on polymers. In this study, we employed a novel alternative protocol incorporating dengue virus particles to assist imprinting of DNT. The binding sites and affinity of DNT with dengue surface protein were simulated for enhancing MIP selectivity. Composite MIP sensors were produced and tested to detect explosive molecules including DNT, TNT, and PETN in aqueous solution. Interestingly, the sensor fabricated with DNT template and dengue virus co-imprinting demonstrated improved TNT selectivity as compared to the other MIP sensors. The detection limit of these sensors approached 0.3 ppt.

Design of A NEMS Cantilever Sensor for Explosive Detection

The particular recognition of explosives in countering fear monger dangers and follow explosives has turned into an appallingly progressed and expensive exertion. This happens because of different impacts, similar to the extensive broad assortment of materials which will be used as explosives, the deficiency of basically perceivable marks, and the monstrous assortment of roads by these weapons might be sent and consequently there will be absence of shoddy sensors with high sensitivity and low vapor analyte property. High sensitivity and property joined with the power, to cut down the orchestrating cost of sensors. Misuse age is basic in winning the war an explosives based demonstration of psychological warfare. Nanosensors can possibly satisfy every one of the necessities of an effective stage for the follow identification explosives. Enhance the sensitivity and selectivity of NEMS cantilever for piezo resistive material in Humidity conditions and manufacture Rectangular Shape Omni directional NEMS cantilever cheap IC and Characteristic chip with Real time reenactment utilizing omnicant.

Orthogonal Sensors for the Trace Detection of Explosives

There is a growing need for an electronic trace detection system that can continuously monitor explosives at trace levels in the vapor phase. Triacetone triperoxide (TATP) is a common explosive used by terrorists as the initiator or the energetic material in improvised explosive devices. TATP still goes largely undetected in many densely populated public venues. Currently, no detection system exists that is capable of continuously monitoring TATP, as well as nitrogen-based explosives such as 2,4-dinitrotoluene. We have demonstrated a thermodynamic sensor platform employing thin film microheaters and metal oxide catalysts that can detect TATP and 2,4-DNT at the parts per billion (ppb) level. The microheaters and catalysts were deposited onto ultrathin alumina ceramic substrates, which are responsible for extraordinary sensitivity. Recently, we have added a conductometric sensor platform to this thermodynamic platform to form an orthogonal sensor capable of interrogating the same catalyst using two different modalities. The orthogonal sensor probes the same catalyst using a thermodynamic protocol, as well as a conductometric protocol where electrical resistivity changes in the catalyst are measured as a function of analyte exposure. The advantages of this added orthogonality in terms of mitigating false-positives and negatives are described within.

Quantitative and rapid detection of explosives using an efficient luminogen with aggregation-induced emission characteristics

The development of fluorescent sensors for explosive detection with high sensitivity is of great importance for antiterrorism and environmental protection. A new efficient AIE luminogen, abbreviated as TPE-SFX, is designed and synthesized. It enjoys typical AIE features and high solid-state fluorescence quantum yield. It can be fabricated into fluorescent dots for explosive detection with good selectivity and rapid response. The fluorescence quenching process and mechanism are investigated. Taking advantage of its high solid-state fluorescence efficiency, TPE-SFX is further utilized on filter paper as solid-state sensor. Through analysis of grayscale variation of fluorescence images, a simple and reliable method is developed for quantitative analysis of picric acid (PA) with a low detection limit to 0.12 nmol/cm2. It is the first report of efficient luminogen utilized on filter paper for quantitative analysis of explosives with high sensitivity. Moreover, the fluorescent filter paper can be regenerated through an environmentally benign method simply by washing with water. In addition, the fluorescent filter paper enjoys good thermal stability, which can endure a high temperature up to 100 °C. These good results will shed some light on the development of quantitative, sensitive, and portable devices for in situ explosive detection in the environment.

Optofluidic laser explosive sensor with ultralow detection limit and large dynamic range using donor-acceptor-donor organic dye

Due to the significance of explosive detection for homeland security and environmental protection, the research of new materials and new methodologies for sensing electron-deficient explosive nitryl aromatics is urgently imperative. In this paper we demonstrate an optofluidic laser sensor for explosive detection by using a highly electron-rich dye (dye-1) with donor-acceptor-donor conjugated structure. The design and facile synthesis process of dye-1 are described. Theoretical calculations, UV–vis absorption and fluorescence spectra are investigated to understand the structure-property relations. Exceptionally high quantum yield of emission in solution is achieved. As a proof of concept, electron-deficient explosive molecule 2, 4-dinitrotoluene (DNT) is used as a model analyte to evaluate the performance of the optofluidic laser sensor. Experimental results indicate that the optofluidic dye laser sensor achieves a large dynamic range with 4 orders of magnitude and an ultralow limit of detection (10 nM), much better than fluorescent sensor. This work provides a route to expand the applications of optofluidic laser for sensitive biochemical detection through specific luminescent materials.

One-pot synthesis of high-density Pd nanoflowers decorated 3D carbon nanotube-graphene network modified on printed electrode as portable electrochemical sensing platform for sensitive detection of nitroaromatic explosives

The maintenance of public security from warfare agents stimulates the growing demand in the development of portable sensors for explosives detection. In this work, a portable electrochemical sensor integrated with a nanohybrid modified printed electrode and miniaturized electrochemical readout, has been established for highly sensitive and rapid in situ detection of explosives. For the preparation of the modified printed electrode, the active electrode material Pd nanoflowers (PdNFs) decorated carbon nanotubes (CNTs)-graphene nanosheets (GNSs) nanocomposite (PdNFs-CNTs-GNSs) has been synthesized by a facile and effective one-pot chemical reduction and assembly from a mixture of their precursors, this enables the formation of highly dense and well dispersed PdNFs on 3D porous CNTs-GNSs network, which effectively increases the electrode active surface area and improves the electrocatalytic activity. For electrochemical detection of a series of explosive nitroaromatic compounds such as p-nitrophenol (4-NP), dinitrobenzene (DNB), 1-choloro-2,4-dinitrobenzene (Cl-DNB), 2,4-dinitrotoluene (DNT), trinitrobenzene (TNB) and trinitrotoluene (TNT), the developed portable electrochemical sensor with PdNFs-CNTs-GNSs modified printed electrode shows attractive analytical features such as good sensitivity, widely operational linear range for determination, low detection limit and high selectivity, and can be used for the sensitive and accurate measurement of nitroaromatic compounds in environmental samples.

Construction of Functional Hyperbranched Poly(phenyltriazolylcarboxylate)s by Metal-Free Phenylpropiolate-Azide Polycycloaddition.

The 1,3-dipolar cycloaddition of activated internal alkynes with azides has been developed into an efficient polymerization reaction for constructing functional linear 1,4,5-trisubstitued polytriazoles. However, it is rarely employed for the synthesis of hyperbranched polymers. In this work, metal-free polycycloadditions of tris(3-phenylpropiolate)s (1) and tetraphenylethene-containing diazides (2) are performed in dimethylformamide at 100°C for 7 and 12 h, producing hyperbranched poly(phenyltriazolylcarboxylate)s (hb-PPTCs) with high molecular weights and satisfactory regioregularities in good yields. The hb-PPTCs have good solubility in common organic solvents and high thermal stability. They are non-emissive in solutions, but emit intensively upon aggregation, showing an aggregation-induced emission effect. Their aggregates can work as fluorescent sensors for explosive detection with high sensitivity. Furthermore, the polymers can be utilized for the fabrication of 2D fluorescent patternswith high resolution byUVirradiation throughcoppergrid masks.

Oxygen as a Crucial Comonomer in Alkyne-Based Polymerization toward Functional Poly(tetrasubstituted furan)s

Oxygen (O2), one of the most essential gases, is abundant, cheap, nontoxic, and environmentally friendly. However, O2 has not been used as a monomer to synthesize polymers yet, probably because of the difficulty in chain growth. In this paper, we develop a new alkyne-based polymerization in which O2 serves as a comonomer under mild reaction conditions. Functionalized diynes could react with O2 in the presence of Pd(OAc)2/ZnCl2 in N,N-dimethylacetamide (DMAc) and perfluorodecalin under atmospheric oxygen. Soluble poly(tetrasubstituted furan)s with high weight-average molecular weights (Mw up to 14 900) were obtained in high yields (up to 86%). The ratio of isomeric repeating units of P1(m) can be identified by analyzing the components of model reaction products. Moreover, P1(6) could function as a fluorescent sensor for explosive detection with superamplification quenching effect. P2–P5 with conjugated structures possess large two-photon absorption cross sections up to 1570 GM, showing great potential as t...

A Comparison of ACQ, AIE and AEE-Based Polymers Loaded on Polyurethane Foams as Sensors for Explosives Detection.

An aggregation-caused quenching (ACQ)-active polymer (PF), an aggregation-induced emission (AIE)-active polymer (PFTPE) and an aggregation-enhanced emission (AEE)-active polymer (PTTPE) were synthesized by tetraphenylethane (TPE), fluorene and thiophene moieties. Polyurethane (PU) foams modified by PF, PFTPE and PTTPE, namely PU-PF, PU-PFTPE and PU-PTTPE, using ultrasonication-assisted method have been prepared. A comparative study of PU-PF, PU-PFTPE and PU-PTTPE for detection explosives had been performed, and significant fluorescence quenching was observed with the introduction of PA solutions. The as-prepared PU-PF, PU-PFTPE and PU-PTTPE sensors exhibited a superior sensitivity for PA solutions with different concentrations. Remarkably, PU-PF gave a quenching efficiency of 96.2%, higher than 93.5% for PU-PFTPE and 86.7% for PU-PTTPE at a PA concentration of 180 µg·mL−1 in methanol, which was attributed to the effective energy transfer from the fluorophore (PF) to the nitro explosive (PA). This suggested that some ACQ polymers, applied to detect explosives, could afford better performances than AIE or AEE polymers through modification of structures and selection of adequate carriers. At the same time, these chemical sensors can be recycled many times.

Advances on Fluorescent Sensors for Detection of Explosives

Advances on Fluorescent Sensors for Detection of Explosives

Transition-Metal-Doped p-Type ZnO Nanoparticle-Based Sensory Array for Instant Discrimination of Explosive Vapors.

The development of portable, real-time, and cheap platforms to monitor ultratrace levels of explosives is of great urgence and importance due to the threat of terrorism attacks and the need for homeland security. However, most of the previous chemiresistor sensors for explosive detection are suffering from limited responses and long response time. Here, a transition-metal-doping method is presented to remarkably promote the quantity of the surface defect states and to significantly reduce the charge transfer distance by creating a local charge reservoir layer. Thus, the sensor response is greatly enhanced and the response time is remarkably shortened. The resulting sensory array can not only detect military explosives, such as, TNT, DNT, PNT, PA, and RDX with high response, but also can fully distinguish some of the improvised explosive vapors, such as AN and urea, due to the huge response reaching to 100%. Furthermore, this sensory array can discriminate ppb-level TNT and ppt-level RDX from structurally similar and high-concentration interfering aromatic gases in less than 12 s. Through comparison with the previously reported chemiresistor or Schottky sensors for explosive detection, the present transition-metal-doping method resulting ZnO sensor stands out and undoubtedly challenges the best.

Graphene Nanoribbon-Supported PtPd Concave Nanocubes for Electrochemical Detection of TNT with High Sensitivity and Selectivity.

In this work, PtPd concave nanocubes anchored on graphene nanoribbons (PtPd-rGONRs) were successfully fabricated through a hydrothermal process. The structural characterizations confirmed that PtPd concave cubes with an average size of around 11 nm have been successfully synthesized and they are uniformly assembled on the surface of rGONRs. The electrochemical measurements demonstrated that the PtPd-rGONRs composite-modified glassy carbon electrode (GCE) shows much enhanced current signals for TNT reduction, which is 4 and 12-fold higher than rGONRs and bare glassy carbon electrode, respectively. The PtPd-rGONRs exhibited a wide linear range for TNT detection from 0.01 to 3 ppm with the sensing limit of 0.8 ppb. Moreover, the PtPd-rGONRs showed excellent detection stability for the determination of TNT. Most importantly, the PtPd-rGONRs-based electrochemical detection platform can be successfully applied to TNT detection in tap water and real lake water samples. The present study indicates that graphene nanoribbon-supported nanocrystals are promising in designing high performance electrochemical sensors for explosives detection.

Fluorescence quenching of rhodamine 6G by 1,3,5-Trinitroperhydro-1,3,5- triazine entrapped in porous sol–gel silica

Fluorescence quenching of laser dye rhodamine 6G by codoping 1,3,5-Trinitroperhydro-1,3,5-triazine (RDX) in porous sol–gel silica is reported. It was found that the fluorescence intensity of rhodamine 6G decreases with increase in the concentration of RDX. Both the samples, predoped cylindrical shaped and postdoped thick film on glass substrate with RDX show the similar fluorescence quenching behavior. Emission spectra show slight red shifting with the increase in RDX concentration. An electron-transfer donor–acceptor mechanism is proposed for the observed fluorescence quenching. On the basis of these results, candidature of dye doped porous sol–gel silica as a sensor for explosive detection seems to be promising.

Detection of Nitroaromatic Explosives Based on Fluorescence Quenching of Silafluorene- and Silole-Containing Polymers: A Time-Dependent Density Functional Theory Study

Poly(silafluorene-phenylenedivinylene)s and poly((tetraphenyl)-silole- phenylenedivinylene)s are promising materials to be used as chemical sensors for explosives detection. The optoelectronic properties of these polymers as well as their constituent units have been investigated by modeling the properties of their excited states. Natural Transition Orbital analysis and topological ϕS descriptor assessment have been used to qualitatively and quantitatively characterize the physical nature of the transitions constituting the absorption spectra. The main transitions observed in all oligomers are associated to be a π–π* transition of the bridging moiety. Lower energy transitions of charge transfer character are further considered to understand the fluorescence quenching mechanism upon the complexation of these polymers with the analytes. Indeed the charge-transfer character of the first excited state leads to the emergence of thermal deactivation channels and hence to luminescence quenching.