Detection Of TNT Research Articles

Tailoring 3D-printed sensor properties with reduced-graphene oxide: improved conductive filaments.

Thedevelopment of a tailored filament is reportedcomposed of reduced graphene oxide (rGO) and carbon black (CB) in a polylactic acid (PLA) matrix and its use in the production of electrochemical sensors. The electrodes containing rGO showed superior performance when compared with those prepared in the absence of this material. Physicochemical and electrochemical characterizations of the electrodes showed the successful incorporation of both rGO and CB and an improved conductivity in the presence of rGO (lower resistance to charge transfer). As a proof-of-concept, the developed electrodes were applied tothe detection of the forensic analytes TNT and cocaine. The electrodes containing rGO presented a superior analytical performance for both TNT and cocaine detection, showing the lower limit of detection values (0.22 and 2.1µmol L-1, respectively) in comparison withpure CB-PLA electrodes (0.93 and 11.3µmol L-1, respectively). Besides, better-defined redox peaks were observed, especially for TNT, as well as increased sensitivity for both molecules.

Designing an electrochemical aptasensor based on a microstructure porous-covalent organic polymer for the determination of 2,4,6-trinitrotoluen in water and soil samples

A selective electrochemical aptasensor assessment based on a microstructure porous-covalent organic polymer (MP-COP) was introduced and applied for 2,4,6-Trinitrotoluen (TNT) sensing. The synthesis of MP-COP involves the formation of an amide bond by coupling carboxylic acids and amine groups using trimesic acid. The synthesized MP-COP was used to modify the glassy carbon electrode (GCE) due to its ability to enhance electrochemical activity. The GCE is modified with the MP-COP and aptamer to create a sensing substrate, with the goal of improving the aptasensor’s electrochemical performance for TNT detection. Electrochemical impedance spectroscopy, differential pulse voltammetry, and cyclic voltammetry were applied for the evaluation of the introduced aptasensor in [Fe(CN)6]3−/4− probe. Moreover, it was delineated using fourier-transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, Brunauer-Emmett-Teller. The suggested aptasensor for TNT has a limit of detection of 0.0003 pM and the linear range from 0.001 to 100 pM. The usability of the proposed aptasensor for TNT measurement in actual samples was examined with the recovery range from 98.30 to 102.40 %. It seems that the proposed strategy can be expanded to design of electrochemical aptasensors.

A highly sensitive and selective Zn-based luminescent MOF for specific detection of trinitrotoluene in aqueous phase

The existence of nitroaromatic compounds, specifically 2,4,6-trinitrotoluene (TNT), in water reservoirs poses significant health risks, necessitating robust detection and monitoring strategies. In this study, we leverage the exceptional properties of the previously synthesized metal-organic framework (MOF), PUC2 as a highly luminescent probe for selective and sensitive detection of TNT in aqueous media. PUC2 exhibits remarkable luminescence, emitting a vivid blue light, making it an ideal candidate for TNT detection. Our investigations reveal that PUC2 demonstrates outstanding sensitivity, achieving an impressive detection limit of 0.145 μM towards TNT which can be attributed to the robust probe-analyte interactions evident from the quenching constant (Ksv) value of 0.18 × 104M−1. An intriguing aspect of PUC2 is its adaptability to a wide pH range, maintaining its sensing capabilities effectively in aqueous phase with pH levels ranging from 4 to 11. The predominant quenching mechanism in this context appears to be photoinduced electron transfer (PET), with an additional enhancement through Forster resonance energy transfer (FRET). The unique combination of structural features and exceptional sensing capabilities of PUC2 opens up new avenues for environmental monitoring and security applications, highlighting its potential as a highly effective luminescent sensor for detecting hazardous substances like TNT.

Versatile Polymerization-Induced Emission Polymers from Barbier Polymerization of Cinnamic Esters with Tunable Emission.

Cinnamic ester is a common and abundant chemical substance, which can be extracted from natural plants. Compared with traditional esters, cinnamic ester contains α,β-unsaturated carbonyl structure with multiple reactive sites, resulting in more abundant reactivities and chemical structures. Here, a versatile polymerization-induced emission (PIE) is successfully demonstrated through Barbier polymerization of cinnamic ester. Attributed to its abundant reactivities of α,β-unsaturated carbonyl structure, Barbier polymerization of cinnamic esters with different organodihalides gives polyalcohol and polyketone via 1,2-addition and 1,4-addition, respectively, which is also confirmed by small molecular model reactions. Meanwhile, these organodihalides dependant polyalcohol and polyketone exhibit different non-traditional intrinsic luminescence (NTIL) from aggregation-induced emission (AIE) type to aggregation-caused quenching (ACQ) type, where novel PIE luminogens (PIEgens) are revealed. Further potential applications in explosive detection are carried out, where it achieves TNT detection sensitivity at ppm level in solution and ng level on the test paper. This work therefore expands the structure and functionality libraries of monomer, polymer and NTIL, which might cause inspirations to different fields including polymer chemistry, NTIL, AIE and PIE.

Theoretical study on the sensing mechanism of fluorescent probes based on benzimidazole for TNT and TNP detection

Trinitrophenol (TNP) and trinitrotoluene (TNT) stand as the most prevalent nitro-based explosives in our daily lives. Due to the considerable destructive power and significant impact on the environment, the detection of these materials is of great importance. In this study, the sensing mechanism of a novel fluorescent probe towards TNT and TNP was intensively investigated. Initially, the molecular configurations of the probe and the binding products were examined. Subsequently, the recognition interaction and the combination site of the fluorescent probe were determined through energy analysis. By comparing the electronic spectroscopy data and the energy profile, we confirmed that the probe sensing TNP is actually via recognizing its ion. According to the frontier molecular orbital analysis, we attributed the fluorescence quenching of detection products to be the photo-induced electron transfer mechanism.

Enhanced TNT vapor sensing through a PMMA-mediated AIPE-active monocyclometalated iridium(III) complex: a leap towards real-time monitoring.

Based on the explosive nature and harmful effects of nitro-based explosive materials on living beings and the environment, it is extremely important to develop luminescence-based probe molecules for their detection with excellent selectivity and sensitivity. Two AIPE (aggregation-induced phosphorescence emission)-active iridium(III) complexes (M1 and M2) were developed for the sensitive detection of TNT in both contact and non-contact modes. The aggregate solutions of both complexes (M1 and M2 in THF/H2O, 1/9 by volume) detected TNT at the pico-molar (pM) level. These complexes showed greatly enhanced emission intensity while embedded in a PMMA(polymethyl methacrylate) matrix film. The amplified quantum efficiency, improved phosphorescence lifetime, and enhanced porous network of M2-PMMA composite helps to improve the sesitivity of TNT vapor detection. Interestingly, the sensitivity of the detection of TNT by the M2 complex was significantly improved (5-fold) in a PMMA-incorporated complex (CP) with an observed limit of detection (LOD) of 12.8 ppb. From the BET analysis of CP, it was observed that the mesoporous network of CP has an average pore diameter of 8.52 nm and a surface area of 2.03 m2 g-1. The porous network of CP assists in trapping TNT vapor in a polymeric network containing an electron-rich probe (iridium(III) complex, M2), which helps to effectively trap TNT, thus enhancing electronic communication. As a result, significant emission quenching was observed.

Metal organic frameworks with carbon black for the enhanced electrochemical detection of 2,4,6-trinitrotoluene

The sensing of explosives such as 2,4,6-trinitrotoluene (TNT) directly at an explosion site requires a fast, simple and sensitive detection method, to which electrochemical techniques are well suited. Herein, we report an electrochemical sensor material for TNT based on an ammonium hydroxide (NH4OH) sensitized zinc-1,4–benzenedicarboxylate Zn(BDC) metal organic framework (MOF) mixed with carbon black on a glassy carbon electrode. In the solvent modulation mechanism, by merely changing the concentration of NH4OH during synthesis, two Zn(BDC) MOFs with novel morphologies were fabricated via a hydrothermal approach. The as-prepared MOFs were characterized using X-ray powder diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and high-resolution field emission electron microscopy (FESEM) equipped with energy dispersive X-ray spectroscopy (EDS). The different morphologies of the MOFs, and their impact on the performance of the modified electrodes towards the electrochemical detection of TNT was investigated. Under optimum conditions, 0.7–Zn(BDC) demonstrated the best electrochemical response for TNT detection using square wave voltammetry (SWV) with a linear calibration response in the range of 0.3–1.0 μM, a limit of detection (LOD) of 0.042 μM, a limit of quantification (LOQ) of 0.14 μM and a high rate of repeatability. Atomic-scale simulations based on density functional theory authenticated the efficient sensing properties of Zn(BDC) MOF towards TNT. Furthermore, the promising response of the sensors in real sample matrices (tap water and wastewater) was demonstrated, opening new avenues towards the real-time detection of TNT in real environmental samples.

Room-temperature phosphorescence and fluorescence nanocomposites as a ratiometric chemosensor for high-contrast and selective detection of 2,4,6-trinitrotoluene

Reports on using complementary colours for high-contrast ratiometric assays are limited to date. In this work, graphitized carbon nitride (g-C3N4) nanosheets and mercaptoethylamine (MEA) capped Mn-doped ZnS QDs were fabricated by liquid exfoliation of bulk g-C3N4, and by a coprecipitation and postmodification strategies, respectively. Mn-doped ZnS quantum dots were deposited onto g-C3N4 nanosheets through an electrostatic self-assembly to form new nanocomposites (denoted as Mn–ZnS QDs@g-C3N4). Mn–ZnS QDs@g-C3N4 can emit a pair of complementary colour light, namely, orange room-temperature phosphorescence (RTP) at 582 nm and blue fluorescence at 450 nm. After 2,4,6-trinitrotoluene (TNT) dosing into Mn–ZnS QDs@g-C3N4 aqueous solution, and pairing with MEA to generate TNT anions capable of quenching the emission of Mn-doped ZnS QDs, the fluorescence colours of the solution changed from orange to blue across white, exhibiting unusual high-contrast fluorescence images. The developed ratiometric chemosensor showed very good linearity in the range of 0–12 μM TNT with a limit of detection of 0.56 μM and an RSD of 6.4 % (n = 5). Also, the ratiometric probe had an excellent selectivity for TNT over other nitroaromatic compounds, which was applied in the ratiometric test paper to image TNT in water, and TNT sensing under phosphorescence mode to efficiently avoid background interference. A high-contrast dual-emission platform for selective ratiometric detection of TNT was therefore established.

A novel 3D-printed graphite/polylactic acid sensor for the electrochemical determination of 2,4,6-trinitrotoluene residues in environmental waters

Here, lab-made graphite and polylactic acid (Gpt-PLA) biocomposite materials were used to additively manufacture electrodes via the fused deposition modeling (FDM) technique for subsequent determination of the explosive 2,4,6-trinitrotoluene (TNT, considered a persistent organic pollutant). The surface of the 3D-printed material was characterized by SEM and Raman, which revealed high roughness and the presence of defects in the graphite structure, which enhanced the electrochemical response of TNT. The 3D-printed Gpt-PLA electrode coupled to square wave voltammetry (SWV) showed suitable performance for fastly determining the explosive residues (around 7 s). Two reduction processes at around −0.22 V and −0.36 V were selected for TNT detection, with linear ranges between 1.0 and 10.0 μM. Moreover, detection limits of 0.52 and 0.66 μM were achieved for both reduction steps. The proposed method was applied to determine TNT in different environmental water samples (tap water, river water, and seawater) without a dilution step (direct analysis). Recovery values between 98 and 106% confirmed the accuracy of the analyses. Additionally, adequate selectivity was achieved even in the presence of other explosives commonly used by military agencies, metallic ions commonly found in water, and also some electroactive camouflage species. Such results indicate that the proposed device is promising to quantify TNT residues in environmental samples, a viable on-site analysis strategy.

Detection of TNT wastewater by the molecular imprinted porous membrane

In this paper, the preparation scheme of TNT molecularly imprinted porous film and the scheme of TNT identification and detection in wastewater are designed by means of molecular imprinting technology. The molecularly imprinted porous film material was prepared by the self-assembly method, and the TNT residue adsorption was detected by a UV-visible spectrophotometer. The concentration of TNT waste liquid was calculated by absorbance, and the effect of the deviation of ultraviolet spectra of different contents of TNT waste liquid was discussed. The results show that the molecularly imprinted films have high adsorption and specific recognition effect on TNT, which can be used for rapid and sensitive detection of TNT in the waste liquid.

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.

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.

Chemical reduction as a facile colorimetric approach for selective TNT detection by spectrophotometry and photothermal lens spectroscopy

In this study, the simple determination of TNT is achieved through the vivid stable red color products generated after chemically reduction by NaBH4 as a common and accessible reducing/colorimetric reagent. Some other nitroaromatics were impressed under reduction reaction and led to the colorful products. The color of these reduced nitroaromatics were unstable and approximately vanished after some few minutes which ameliorated the selectivity in TNT determination. Utilizing the time-dependent selectivity, the method was applied specifically for discriminating of TNT from other nitroaromatic compounds (NACs). UV–vis spectrophotometry and photothermal lens spectrometry were employed as detection techniques. The former was simpler and more available in various laboratories while the latter provides higher sensitivity. It was revealed that the photothermal lens responses were linear from 2.0 to 55.0 nM with a limit of detection (LOD) of about 0.8 nM. The LOD of the photothermal lens measurement were found to be 241 times lower than that of the UV–vis spectrophotometry in TNT quantification. The evolved method was successfully carried out for TNT vapor determination after trapping into the colorimetric reagent. The recoveries and relative standard deviations (RSD, n = 3) calculated for 3 gas samples were ≥91% and ≤7%, respectively.

A highly sensitive and selective detection of 2,4,6-trinitrotoluene (TNT) using a peptide-functionalized silicon nanowire array sensor.

A highly sensitive and specific detection of 2,4,6-trinitrotoluene (TNT), a typical nitrated aromatic explosive, was demonstrated by a silicon nanowire (SiNW) array sensor. The SiNW array devices were self-assembled and functionalized with the anti-TNT peptide to obtain unique sensitivity toward TNT. Also, the effect of the biointerfacing linker's chemistry and Debye screening with varied ionic strength of phosphate buffer solution (PBS) on TNT binding response signals were investigated. The optimization of the peptide-functionalized SiNW array sensor showed high sensitivity for TNT with a detection limit of 0.2 fM, the highest sensitivity reported to date. These initial promising results may help accelerate the development of portable sensors for femtomolar level TNT detection.

A novel pyrenyl-furan hydrazone on paper-based device for the selective detection of trinitrotoluene

T2 paper-based sensor detection of TNT was linear from 30–500 μM with a detection limit of 30 μM. The T2 paper-based sensor can detect TNT with high selectivity and sensitivity.

Microwave spectra of dinitrotoluene isomers: a new step towards the detection of explosive vapors.

The spectroscopic characterization of explosive taggants used for TNT detection is a research topic of growing interest. We present a gas-phase rotational spectroscopic study of weakly volatile dinitrotoluene (DNT) isomers. The pure rotational spectra of 2,4-DNT and 2,6-DNT were recorded in the microwave range (2-20 GHz) using a Fabry-Perot Fourier-transform microwave (FP-FTMW) spectrometer coupled to a pulsed supersonic jet. Rotational transitions are split by hyperfine quadrupole coupling at the two 14N nuclei leading to up to 9 hyperfine components. The spectral analysis was supported by quantum chemical calculations carried out at the B98/cc-pVTZ and MP2/cc-pVTZ levels of theory. Based on 2D potential energy surfaces at the B98/cc-pVTZ level of theory, the methyl group internal rotation barriers were calculated to be V3 = 515 cm-1 and 698 cm-1 for 2,4- and 2,6-DNT, respectively. Although no splitting due to internal rotation was observed for 2,6-DNT, several splittings were observed for 2,4-DNT. The microwave spectra of both species were fitted using a semi-rigid Hamiltonian accounting for the quadrupole coupling hyperfine structure. Based on the internal axis method (IAM), an additional analysis was performed to retrieve an accurate value of the rotationless A-E tunneling splitting which could be extracted from the rotational dependence of the tunneling splitting. This yielded in the case of 2,4-DNT to an experimental value of 525 cm-1 for the barrier height V3 which agrees well with the DFT value. The coupled internal rotations of -CH3 and -NO2 are investigated in terms of 2-D surfaces, as already done in the case of 2-nitrotoluene [A. Roucou et al., Chem. Phys. Chem., 2020, 21, 2523-2538].

A flow-drop electrochemiluminescent design for portable detection of soil and skin 2,4,6-trinitrotoluene

An automatic miniaturized flow-drop electrochemiluminescence (ECL) technique was established by utilizing a coalescing drop as a wall-less electrolytic cell, a self-driven mixer, and a µL scale reactor. Cost-effective ECL detection of 2,4,6-trinitrotoluene (TNT) was proposed, by virtue of the finding of the enhancement on luminol ECL by trace TNT in alkaline aqueous medium. The mechanism of TNT intensifying luminol ECL was suggested as that the one-electron reduction of TNT yielded TNT anion radical converts dissolved oxygen into superoxide anion radical, which subsequently reacted with luminol to produce luminol anion radical, finally resulting in the acceleration of luminol oxidation. By optimizing all the experimental conditions, the intensified ECL was found to be linear to TNT concentration over the 5–100 nM range, with a limit of detection of 0.5 nM. The method’s precision and accuracy were examined via F and t tests. The feasibility of this portable ECL method was validated by determining unknown TNT contents in real soil and finger skin samples via parallel official method. All results support the technique as a robust alternative for on-site TNT detection for environmental and forensic purposes.

Vapor-Phase Substrate Nitroreductase Reaction and Its Application as TNT Electrochemical Gas Sensor

Nitroreductase (NTR) is an enzyme that specifically reduces nitroaromatic activity. Some nitroaromatic explosives are exploited by terrorists. Among these highly explosive materials, 2,4,6-trinitrotoluene (TNT) is often used, which makes the detection of TNT an important research topic in the fight against terrorism. TNT vapor detection by gas sensor is an approach that has been under active investigation for several years. Despite this effort, presently, there is limited practical success, in part, due to the ultralow volatility nature of TNT. In this work, we propose an application of the NTR reaction in a hydrogel gas sensor to detect TNT vapor. First, NTR activity in the hydrogel was confirmed by adding TNT and 2,4-dinitrotoluene (DNT) solutions to the NTR-hydrogel sensor conducting cyclic voltammetry (CV) experiments. Then, further CV experiments were carried out with gas phase samples. The CV graphs of NTR-hydrogels detecting vapors containing the explosive substrates and negative controls were compared. Results showed that the signal from the nitroaromatics increased with exposure time, where the TNT signal was the highest of all tested compounds. The gas sensor was sensitive enough to detect TNT gas presented in an ambient air at room temperature.

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.

Selective determination of 2,4,6-Trinitrotoluene (TNT) with cysteamine in deep eutectic solvents

2,4,6-trinitrotoluene (TNT) is one of the most widely used explosives for military and civilian purposes. Detection of TNT is very important for both human health and public safety. In this study, TNT determination was carried out using a new solvent medium containing cysteamine (CysN) without the need for noble metal nanoparticles (i.e. CysN-AuNPs used for anchoring CysN through S-atom) or strong alkalinity (i.e. to stabilize TNT-Meisenheimer anions in aqueous medium). CysN was prepared in a deep eutectic solvent (DES) consisting of a mixture of choline chloride and ethylene glycol, and the color of the Meisenheimer complex was derived from the donor–acceptor interaction between the amine group on CysN and the nitro group on TNT. The Lewis base-acid neutralization product, CysN-TNT charge-transfer complex, was stable in the optimized DES solvent unlike that in water. The absorbance of the resulting red complex was measured at 515 nm. The LOD and LOQ values were found to be 67.17 and 223.90 μg L− 1, respectively. The proposed method was not affected by similar explosives, camouflage agents, and possible ion interference in the soil. Finally, the method was validated with an HPLC-DAD analysis. This method is the first study to use DESs in the determination of energetic materials such as TNT and the proposed assay shows excellent selectivity for TNT. The proposed method stands out as it is fast, simple, of low cost, compatible with green chemistry with the potential to convert to a paper-based colorimetric sensor.