TNT Molecules Research Articles

Adsorption and Detection of 2,4,6-Trinitrotoluene by New Two-Dimensional BCN Monolayers: A First-Principles Study

Three predicted new two-dimensional (2D) boron carbon nitrogen (BCN) structures, named B8C2N8, B6C6N6-1, and B6C6N6-2, are investigated theoretically. The stability and electronic properties of the three structures are explored. The results reveal that three 2D BCN structures are dynamically, thermodynamically, and mechanically stable. B8C2N8 is a direct semiconductor with a band gap of 1.76 eV, B6C6N6-1 is an indirect semiconductor with a band gap of 0.21 eV, and B6C6N6-2 exhibits metallic properties. B6C6N6-1 shows a transition from semiconductor to conductor under an external strain. The large adsorption energies of TNT adsorbed on BCN reveal that it is feasible to use 2D BCN materials to adsorb TNT. Among the three BCNs, due to the largest band gap variation and the largest charge transfer amounts, B8C2N8 has an outstanding performance in terms of the adsorption of TNT and is expected to be used to detect TNT or other nitro molecules.

Trace Explosive Detection Based on Photonic Crystal Amplified Fluorescence.

With increasing demand for public security and environmental protection, it is highly desirable to develop strategies to identify trace explosives (e. g., 2,4,6-trinitrotoluene (TNT)). Herein, we report novel photonic crystal (PC)-based sensor chips for trace TNT detection by using amplification effect of PCs on fluorescence (FL) signals. The sensor chips are constructed by integrating silica nanoparticles (NPs) modified with (3-aminopropyl)triethoxysilane (APTES) and fluorescein isothiocyanate isomer (FITC) and PC substrates. The amino groups on FITC-APTES-silica NPs can specifically bind with TNT molecules to form Meisenheimer complexes and strongly quench the FL signal of neighboring fluorophores FITC through Förster resonance energy transfer. PCs with matched PBG can amplify the FL signal of FITC-APTES-silica NPs about 24.4-fold and significantly improve sensitivity and resolution of trace TNT detection with the limit of detection of 0.23 nM. The PC-based sensor chips are stable, sensitive, and reliable TNT sensing platforms, showing great potential in homeland safety and environmental protection.

Efficient adsorption of trinitrotoluene by isoxazoline‐based porous polymers prepared from room‐temperature stable bis(nitrile oxide)

AbstractA novel isoxazoline‐based porous adsorbent (PB‐TTNO) is prepared by click polymerization and freeze‐drying from a methyl‐containing bis(nitrile oxide) stable at room temperature. The introduction of four methyl groups around the nitrile oxide group reduces the activity of the bis(nitrile oxide) and make it react more mildly with polybutadiene, resulting in PB‐TTNO with a more uniform pore size. Meanwhile, the electron‐donating methyl groups further increase the π–π interaction between the polymer benzene ring and the TNT benzene ring. The π–π interaction enables one benzene ring in the polymer to interact with two TNT molecules to form a sandwich structure, which further improves the adsorption capacity. The synergistic effect of dual π–π interactions and dipole‐π interactions makes the maximum adsorption capacity of PB‐TTNO reach 235.3 mg g−1 within 12 h at 25°C. The factors such as pH value, adsorbent dosage, contact time, initial TNT concentration, and temperature are also discussed. The adsorption kinetics fit well with the pseudo‐second‐order model, and the Langmuir model exhibits better correlation for equilibrium data analysis. In addition, the adsorption data of PB‐TTNO in real water samples are similar to those in laboratory, and the maximum adsorption capacity decreases by only 15% after five adsorption–desorption cycles.

Smartphone-Assisted Sensing of Trinitrotoluene by Optical Array.

Here we report the design and fabrication of an array-based sensor, containing functionalized Carbon Dots, Bodipy’s and Naphthalimide probes, that shows high fluorescence emissions and sensitivity in the presence of low amounts of TNT explosive. In particular, we have fabricated the first sensor device based on an optical array for the detection of TNT in real samples by using a smartphone as detector. The possibility to use a common smartphone as detector leads to a prototype that can be also used in a real-life field application. The key benefit lies in the possibility of even a nonspecialist operator in the field to simply collect and send data (photos) to the trained artificial intelligence server for rapid diagnosis but also directly to the bomb disposal unit for expert evaluation. This new array sensor contains seven different fluorescent probes that are able to interact via noncovalent interactions with TNT. The interaction of each probe with TNT has been tested in solution by fluorescence titrations. The solid device has been tested in terms of selectivity and linearity toward TNT concentration. Tests performed with other explosives and other nitrogen-based analytes demonstrate the high selectivity for TNT molecules, thus supporting the reliability of this sensor. In addition, TNT can be detected in the range of 98 ng∼985 μg, with a clear different response of each probe to the different amounts of TNT.

Sublimation and Diffusion Kinetics of 2,4,6-Trinitrotoluene (TNT) Single Crystals by Atomic Force Microscopy (AFM).

In this article, we report the in-situ nanoscale experimental measurement of sublimation rates, activation energy of sublimation, and diffusion coefficients of 2,4,6-trinitrotoluene (TNT) single crystals in air using atomic force microscopy (AFM). The crystals were prepared by slow evaporation at 5 °C using acetone-dissolved TNT. The mass loss was calculated by monitoring the shrinkage of the surface area of layered islands formed on the surface of the TNT crystals due to sublimation upon isothermal heating at temperatures below the melting point. The results suggest the sublimation process occurs via two-dimensional detachment of TNT molecules from the non-prominent facets on the crystal surface which imitates the nucleation and crystal growth process. Sublimation rates are one order of magnitude smaller than previously reported values. However, the calculated activation energy (112.15 ± 3.2 kJ/mol) and temperature-dependent sublimation rates agree well with the reported values for TNT thin films and microcrystals determined by UV-vis absorbance spectroscopy and quartz crystal microscopy (QCM) (90–141 kJ/mol). The average diffusion coefficient is (4.35 × 10–6 m2/s) which is within the range of the reported theoretical values with an average of 5.59 × 10–6 m2/s, and about 25% less than that determined using thermogravimetric analysis for powder TNT.

The Nano Silver Molecules Enhancing the Trinitrotoluene Phytoremediation Using Potato Crop

Phytoremediation represents a great technique that uses green plants in the partial analysis of explosive compounds existing in soil via a variety of biochemical properties in plants to help manipulate contamination. The study was done to determine the effect of using nanosilver molecules and toluene concentrations for botanic manipulation and how to influence physiological growth characters of potato. A field experiment was done in the woody roof shade of Gardening and Farming Dept., Agriculture College, University of Anbar for the spring season 2021 on potato crop, and the study included the botanic manipulation review in different levels of trinitrotoluene and different concentrations of nanosilver molecules on some physiological properties, using simple experiments (mixes of TNT and nanosilver molecules) within the randomized complete block design in three replications as 30 experimental units. results revealed that 500 mg TNT kg-1 soil + 500 mg NPs kg-1 dominated in total nitrogen, phosphorus and potassium percentage in averages 1.92%, 0.58%, 1.85% successively, compared with the control treatment which was noticed in in chlorophyll A, B and total chlorophyll estimation, that successively scored (45.76, 27.13, 87.50 mg/100g) to the scores of control treatment (35.70, 20.83, 71.50 mg/100g). from the study, we conclude that the treatment at level (500*500 TNT-NPS) has a positive effect on physiological properties of the studied potato.

Photolysis by UVA-visible light and thermal degradation of TNT in aqueous solutions according to aerodynamic thermal breakup droplet ionization mass spectrometry

The mechanism of photolytic degradation of 2-4-6-trinitrotoluene (TNT) in an aqueous solution (initial concentration 102 mg L−1) by UVA-visible light (>320 nm) was investigated by aerodynamic thermal breakup droplet ionization mass spectrometry. For photolysis, a DRK-120 mercury-quartz lamp was used. The final and intermediate products of the photolysis reaction were compared with known products of TNT transformation in the environment. The first step in the photolysis process under our conditions was found to be the association of TNT molecules into a fairly stable dimer. The TNT dimer formation proceed through the formation of a Meisenheimer complex. Thermal degradation of the TNT dimer in microdroplets within a heated capillary used as a flow reactor was studied next. It was shown that the degradation of the TNT dimer in microdroplets occurs very quickly (2.1 ms) at heating (up to 200–250 °C). Of course, heating an aqueous aerosol requires energy, but the transformation of TNT can be controlled using a combination of photo- and thermal treatments. We hope that these results will help to reduce the toxicity of TNT contaminants and remove nitroaromatic compounds from water at ambient conditions. In this work, the TNT dimer formed at the first stage is transformed with the loss of NO2 fragments or water. In addition, further polymerization of TNT is observed.

Influence of Air Flow on Luminescence Quenching in Polymer Films towards Explosives Detection Using Drones.

Explosive detection has become an increased priority in recent years for homeland security and counter-terrorism applications. Although drones may not be able to pinpoint the exact location of the landmines and explosives, the identification of the explosive vapor present in the surrounding air provides significant information and comfort to the personnel and explosives removal equipment operators. Several optical methods, such as the luminescence quenching of fluorescent polymers, have been used for explosive detection. In order to utilize sensing technique via unmanned vehicles or drones, it is very important to study how the air flow affects the luminescence quenching. We investigated the effects of air flow on the quenching efficiency of Poly(2,5-di(2′-ethylhexyl)-1,4-ethynylene) (PEE) by TNT molecules. We treated the TNT molecules incorporated into the polymer film as non-radiative recombination centers, and found that the time derivative of the non-radiative recombination rates was greater with faster air flows. Our investigations show that relatively high air flow into an optical sensing part is crucial to achieving fast PL quenching. We also found that a “continuous light excitation” condition during the exposure of TNT vapor greatly influences the PL quenching.

Thermal decomposition mechanisms of benzotrifuroxan:2,4,6-trinitrotoluene cocrystal using quantum molecular dynamics simulations

Density functional tight-binding molecular dynamics simulations with dispersion corrections were performed to study the thermal decomposition mechanisms of benzotrifuroxan: 2,4,6-trinitrotoluene (BTF:TNT) cocrystal at 2400 and 2700 K. The TNT molecules are easier to decompose, which promotes the initial decomposition of the cocrystal. The furoxan ring opening by the NO bond cleavage is the initial reaction step of BTF, while the CNO2 homolysis and NO2 rearrangement of TNT are the main decomposition paths. The rate constants of the BTF and TNT decomposition were obtained by analyzing the decomposition kinetics of the cocrystal using the first order rate model.

The thermal decomposition behavior of the TNT‐RDX‐Al explosive by molecular kinetic simulation

AbstractThe TNT‐RDX‐Al Explosive is an aluminum‐containing mixed explosive often used in civil and military equipment, but the decomposition mechanism has not been theoretically studied. In this paper, the reaction force field containing C/H/O/N/Al parameters was used to simulate the thermal decomposition of the TNT‐RDX‐Al Explosive by reaction kinetics simulation. And the results were compared with the thermal decomposition behaviors of the binary systems TNT/AlO RDX/AlO and TNT/RDX. The partially passivated nano‐aluminum particles were constructed and then mixed with TNT supercell, RDX supercell, and the constructed TNT/RDX supercell. The obtained mixed systems were then heated to a high temperature, where the explosive was completely decomposed. The decomposition process of the TNT‐RDX‐Al Explosive can be divided into several stages: the adsorption of aluminum atoms on TNT molecules and RDX molecules, the diffusion of O atoms into nano aluminum particles, the decomposition of TNT molecules and RDX molecules, the diffusion of C, H, N atoms into the nano aluminum particles, the Al atoms in the center of the aluminum sphere diffuse outward, and the final stage is the formation of the final product. The results show that the aluminum nanoparticles in the ternary system are easier to diffuse and spreads more widely. The addition of RDX molecules advances the time to complete decomposition of TNT molecules, and promotes the time when TNT molecules is completely decomposed to be closer to the time when RDX molecules is completely decomposed.

Nanocellulose-based Surface-enhanced Raman spectroscopy sensor for highly sensitive detection of TNT

Surface-enhanced Raman scattering (SERS) has undergone an important development in the detection and identification of extremely low traces of explosives over the past few years. Here we fabricated a new type of three-dimensional (3D) SERS sensors by loading AuNR@AgNCs on bacterial cellulose aerogels for the detection of 2, 4, 6-trinitrotoluene (TNT). The aerogel substrates with hierarchical pore structure are favored by the construction of dense 3D hot-spot distribution and the enrichment of TNT molecules. The retention aid of polyethyleneimine was used to improve the loading capacity as well as prevent the aggregation of nanoparticles. Moreover, AuNR@AgNCs were modified with p-aminobenzenethiol to improve the affinity of SERS substrates to TNT via the formation of Meisenheimer complex. Owing to the unique structure and morphology of AuNR@AgNCs, the composite SERS substrate can detect trace TNT with a limit of detection of 8 × 10−12 g/L and the SERS enhancement factor is high up to 1.87 × 108.

A SERS stamp: Multiscale coupling effect of silver nanoparticles and highly ordered nano-micro hierarchical substrates for ultrasensitive explosive detection

In this study, we reported a novel highly ordered nano-micro hierarchical structure on flexible polydimethylsiloxane (PDMS) layer as a SERS stamp for ultrasensitive detection, which can generate huge SERS signals with silver nanoparticles (AgNPs) owing to a multiscale coupling electromagnetic enhancement mechanism. Highly ordered nanowrinkles were prepared by oxygen plasma and stretching treatment of PDMS. Indeed, a tactfully designed zigzag micropattern can efficiently reduce the fracture defects of nanowrinkles because the contraction force can be lessened at releasing step. This proposed substrate has high reproducibility and uniformity that the relative standard deviation (RSD) was below 7 %. With uniform hot spots on this novel flexible SERS substrate, 2, 4, 6-trinitrotoluene (TNT) residues can be detected on coarse surfaces of target item. A molecule interaction mechanism of Meisenheimer complex was applied to combine AgNPs and nanowrinkles for highly sensitive detecting TNT. The detection sensitivity of TNT molecules can achieve a limit of 10−13 mol L−1. Additionally, a practical application was proceeded by wiping the cloth bag to detect the TNT residues with a limit of 10−9 mol L−1. This demonstrated stamp-like flexible substrate showed unique SERS activity and non-invasive sampling, it is expected to be a promising tool for the explosive, drug and environmental pollutant in field-detection.

Intermolecular interactions, vibrational spectra, and detonation performance of CL‐20/TNT cocrystal

AbstractWe report the structural properties, intermolecular interactions (Hirshfeld surface analysis and reduced density gradient [RDG] analysis), radial distribution function analysis, vibrational frequencies, and detonation performance for the pure ε‐CL‐20, TNT, and ε‐CL‐20/TNT cocrystal to understand how noncovalent interactions affect the impact sensitivity of the cocrystals. The results indicate that the simulated lattice parameters and densities of all the three crystals were consistent with the experiments. Major driving forces for the formation of the ε‐CL‐20/TNT cocrystal are OH and NO interactions, but the OO interactions may serve as a crucial stabilizing force. The calculated Raman spectra of the CL‐20/TNT cocrystal and the experimental result have the same trend. The Roman peaks of the cocrystal in the range 1,200–1,750 cm−1 may result from the coupling of the ε‐CL‐20 and TNT molecules. Similar crystal packing for TNT and CL‐20 leads to the high density for the cocrystal. The cocrystal displays low impact sensitivity because of the p–π interactions. Our work may offer useful information for cocrystallization technology and its practical applications in the field of energetic materials.

Light trapping induced flexible wrinkled nanocone SERS substrate for highly sensitive explosive detection

We reported an ultrasensitive TNT detection method via a novel light trapping induced wrinkled nanocone flexible SERS substrate, which was fabricated by colloidal lithography and oxygen plasma etching on transparent PET film. Especially, a set of nanowrinkles with 50−60 nm was found on the sidewall of nanocone after etching. By coating 30 nm gold film, this flexible SERS substrate provided uniform hot spots, which demonstrated high reproducibility and sensitivity. 4-ATP molecules based Meisenheimer complex, which is a well-known charge-transfer interaction between electron-poor TNT and electron-rich amino group, was taken to detect ultra-low concentration of TNT explosive. The Raman signal of TNT was significantly enhanced by charge-transfer, light trapping effect and coupled electromagnetic field. The detection sensitivity of TNT molecules was as low as 10−13mol/L, and show a good linear response in the range from 10−8 to 10−13mol/L. Consequently, by brushing this flexible SERS substrate onto a cloth bag, trace amount of TNT residues with concentration as low as 10-10mol/L can be easily analyzed. It is believed that the proposed highly sensitive and uniform flexible substrate provides a significant solution for trace analysis of TNT residue in criminal forensic, military and security check.

Detection of TNT in sulfuric acid solution by SiNWs-FET based sensor

Since the preparation of TNT is always proceeded in acid solution, it is very difficult to accurately detect it at the production stage. Developing a TNT sensor which can work in sulfuric acid solution will be very helpful. This paper presents a TNT sensor based on SiNWs-FET which can quickly detect TNT in sulfuric acid. The detection mechanism is based on the fact that TNT molecules can selectively bond to the amino group of nanowires, which act as grid elements and modulate the conductance of the silicon nanowires, leading to the variation of SiNWs-FET drain-source current. The SiNWs-FET devices were fabricated on a (111) silicon-on-insulator wafer using controllable silicon anisotropy etching and self-limiting oxidation. The silicon nanowires were treated with oxygen plasma and 3-aminopropyltriethoxysilane (APTES) to form hydroxyl and amino groups on the surface of the nanowires, respectively. The SiNWs-FET sensor demonstrated highly sensitive detection to TNT molecule in aqueous solution with 0.1% dimethyl sulfoxide (DMSO) and sulfuric acid solutions. These experimental results show that the SiNWs-FET sensor can work stably and reliably in some harsh environment, even in high concentration of sulfuric acid. The rapid response time also reflected the advantages of SiNWs-FET sensors in TNT fast detection. In addition, the SiNWs-FET sensor showed selectivity to TNT, due to the specific bind between amino groups and nitro groups.

Faster and Cleaner Method to Mass Produce Nano HMX/TNT Energetic Particles for Significantly Reduced Mechanical Sensitivity.

Mechanochemical method is an environmentally friendly approach, which can facilely synthesize large-scale nano-scale HMX/TNT energetic particles. In the mechanochemical process, a large new structure was obtained by solid-state grinding of a starting physical mixture HMX and TNT in the presence of ethanol. Within the resulting nano HMX/TNT energetic particles, HMX and TNT molecules are crystallographically rearranged after IR and X-ray irradiation. The size and microstructure were characterized using scanning electron microscopy (SEM). The thermal decomposition of the energetic particles was analyzed using differential scanning calorimetry (DSC). Simultaneously, explosive property and impact safety performance tests and analysis were conducted. Results showed that nano HMX/TNT energetic particles offer a number of advantages in comparison with raw HMX and raw TNT including decreased size, stable thermal performance, reduced sensitivity and improved explosive property after the mechanochemical technology.

Janus-micromotor-based on-off luminescence sensor for active TNT detection.

An active TNT (2,4,6-trinitrotoluene) catalytic sensor based on Janus upconverting nanoparticle (UCNP)-functionalized micromotor capsules, displaying “on–off” luminescence with a low limit of detection has been developed. The Janus capsule motors were fabricated by layer-by-layer assembly of UCNP-functionalized polyelectrolyte microcapsules, followed by sputtering of a platinum layer onto one half of the capsule. By catalytic decomposition of hydrogen peroxide to oxygen bubbles, the Janus UCNP capsule motors are rapidly propelled with a speed of up to 110 μm s−1. Moreover, the Janus motors display efficient on–off luminescent detection of TNT. Owing to the unique motion of the Janus motor with bubble generation, the likelihood of collision with TNT molecules and the reaction rate between them are increased, resulting in a limit of detection as low as 2.4 ng mL−1 TNT within 1 minute. Such bubble-propelled Janus UCNP capsule motors have great potential for contaminated water analysis.

Recent advances in electrochemical sensors for the detection of 2, 4, 6-trinitrotoluene

2, 4, 6-Trinitrotoluene (TNT) is a frequently used explosive compound, and it easily gathers in soil and water during transportation, use, and storage. Except for the security issue, it also has high toxicity and mutagenic effect on the environment and all life forms. Thus, it is critical to develop high-efficiency sensing methods for the detection of TNT at trace levels with high sensitivity and selectivity. This brief review highlights the research progress of using electrochemical sensors to analyze TNT molecules in recent years. Specifically, this minireview mainly focuses on the recently developed nanostructured electrocatalysts and electrochemical methods combined with other techniques for electrochemical detection of TNT.

Reactive molecular dynamics simulation of thermal decomposition for nano-AlH3/TNT and nano-AlH3/CL-20 composites

Using reactive molecular dynamics method with the reactive force field framework, the thermal decomposition of nano-AlH3/TNT and nano-AlH3/CL-20 composites was investigated to develop new high explosives. The binding energies and relaxed densities of the composites show that the compatibility of TNT/AlH3 is better than CL-20/AlH3, which is confirmed by the DFT calculations. The pyrolysis simulations showed that the potential barrier of TNT/AlH3 (1.14 kJ g−1) and CL-20/AlH3 (0.72 kJ g−1) are smaller than pure TNT (1.99 kJ g−1) and pure CL-20 (1.01 kJ g−1), respectively. This indicates the catalytic effect of AlH3 nanoparticle on the decomposition of TNT and CL-20. The catalytic effect was confirmed by the DFT calculations of the R–NO2 rupture of TNT and CL-20 molecules on AlH3 surfaces. The slower heating rate (rh) of 16 K ps−1 led to similar evolution results as rh = 32 K ps−1, which implies that the dependence of the simulation results on the heating rate is small. Moreover, TNT/AlH3 and CL-20/AlH3 release 1.07 and 1.97 kJ g−1 more energies and generate 33.8% and 14.0% more total gas products than pure TNT and CL-20, respectively. Therefore, AlH3 nanoparticles can improve the detonation performance and specific impulse for TNT and CL-20. These are in accord with the effect of AlH3 on nitromethane and ammonium perchlorate/hydroxyl-terminated polybutadiene propellants in the experiments. As a result, the nano-AlH3/TNT and nano-AlH3/CL-20 composites can be promising candidates of new high explosives.

ReaxFF molecular dynamics simulations of shock induced reaction initiation in TNT

Thermodynamic pathways and reaction initiation mechanisms of shocked TNT (2, 4, 6-trinitrotoluene, formula C6H2(NO2)3CH3) with shock velocities in the range of 6 -10 km⋅s-1 using the first-principles-based ReaxFF reactive force field molecular dynamics and the multiscale shock technique (MSST) are reported in this paper. The decomposition reactions occur at a shock velocity of 7 km⋅s-1 or higher. The shock initiation pressure, 25.1 GPa, is obtained from Rankine−Hugoniot relation. According to the link between macroscopic shock initiation and microscopic chemical reaction events, the formation of TNT-dimer and decomposition to C7H5O5N3 are the dominant initial route for shock induced reaction initiation. At shock speeds equal to or higher than 8km⋅s-1, TNT-dimer is formed and subsequently decomposed to C7H5O5N3, NO2 and NO. The quantity of NO2 molecules reaches maximum when TNT molecules decompose completely. Furthermore, when NO2 molecules are consumed fully, the volume of reaction system begins to expand. TNT molecules are dimerized at each shock condition, and the quantity of dimers is the largest at a shock initiation velocity of 7 km⋅s-1. Finally, the formation and evolution of carbon-containing clusters in shocked TNT are analyzed.