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Fluorescence probe technology holds great promise in the application of trace explosive detection due to its high sensitivity, fast response speed, good selectivity, and low cost. In this work, a designed approach has been employed to prepare the TPE-PA-8 molecule, utilizing the classic aggregation-induced emission (AIE) property of 1,1,2,2-tetraphenylethene (TPE), for the development of self-assembled monolayers (SAMs) targeting the detection of trace nitroaromatic compound (NAC) explosives. The phosphoric acid acts as an anchoring unit, connecting to TPE through an alkyl chain of eight molecules, which has been found to play a crucial role in promoting the aggregation of TPE luminogens, leading to the enhanced light-emission property and sensing performance of SAMs. The SAMs assembled on Al2O3-deposited fiber film exhibit remarkable detection performances, with detection limits of 0.68 ppm, 1.68 ppm, and 2.5 ppm for trinitrotoluene, dinitrotoluene, and nitrobenzene, respectively. This work provides a candidate for the design and fabrication of flexible sensors possessing the high-performance and user-friendly detection of trace NACs. [ABSTRACT FROM AUTHOR]

• PUC2 Luminescent Probe: utilizing MOF PUC2 for TNT detection. • Sensitivity: achieving a 0.145 μM detection limit. • pH Adaptability: effective in pH 4–11 aqueous environments. • Distinctive Blue Emission: vivid blue light enhances accuracy. • Quenching Mechanisms: PET and FRET for sensitivity. 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 × 104 M −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. [Display omitted] [ABSTRACT FROM AUTHOR]

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Naphthalimide‐hydroxyquinoline based conjugates (NQ1 and NQ2) were synthesized for the detection of nitroaromatics in HEPES buffer/DMSO (9/1, v/v, pH=7.4) and Fe3+/Pd2+ in CH3CN solvent. The NQ1 and NQ2 were characterized using NMR (1H, 13C, COSY) and IR spectroscopies. Theoretical studies revealed that 8‐HQ moiety in NQ1 and NQ2 placed at orthogonal position with respect to naphthalimide core to minimize steric crowding. The energy gap between HOMO and LUMO for NQ1 and NQ2 were found to be −3.1 eV. The emission spectrum of NQ1 and NQ2 showed decrease in the emission intensity at 450 nm upon addition of picric acid (PA) and trinitrotoluene (TNT) whereas addition of 2‐nitroaniline caused quenching with concomitant red‐shift of the emission band in 90 % HEPES buffer‐DMSO. The detection limit of NQ1 for PA, TNT and 2‐NA detection was calculated as 8.7×10−6 M, 2.2×10−5 M and 1.8×10−5 M. The complexation of NQ1 with PA, TNT and 2‐NA was further supported by Job's plot, dynamic light scattering studies and NMR titrations. We successfully utilized NQ1 and NQ2 for the detection of PA, TNT and 2‐NA in real soil samples with excellent recovery. NQ1 also showed quenching of the emission intensity at 450 nm upon addition of Fe3+ and Pd2+ ions in CH3CN. Thus, NQ1 showed solvent‐dependent dual chemosensor type behavior. The functioning of NOR gate has been achieved using Fe3+/NACs with NQ1. [ABSTRACT FROM AUTHOR]

Trinitrotoluene (TNT) is a widely used explosive belonging to the family of nitroaromatic compounds, and its misuse poses a significant threat to society. Herein, we propose a Tb-BSA-AuNC fluorescent and colorimetric sensing probe for the selective onsite detection of TNT in the aqueous phase. Tb-doped BSA-protected gold nanoclusters (Tb-BSA-AuNCs) were synthesized by a microwave-assisted method, and TNT detection was carried out utilizing the chemistry of Meisenheimer complex formation. Tb doping of gold nanoclusters was demonstrated to facilitate better electron shuttling effects and thereby improve the efficiency of complex formation between the TNT and gold nanoclusters. A paper strip assay was also developed for TNT detection with the designed probe. Limits of detection and quantification of 0.2136 mM and 0.7120 mM, respectively, were achieved. [ABSTRACT FROM AUTHOR]

2,4,6-Trinitrotoluene (TNT) is a class C carcinogen as rated by the Environmental Protection Agency. One of the toxicity mechanisms of TNT is the covalent binding of its metabolites to critical proteins. However, knowledge about their molecular reaction mechanisms is scarce. Herein, we have provided density functional theory (DFT) simulation evidences for the reaction mechanisms of the nitroso metabolite of TNT with the sulfhydryl group of model thiols for the first time. The results show that the solvent-mediated proton-transfer mechanism plays a significant role in the entire process. For the formation of semimercaptal, the mechanism is slightly different from the previous one where the thiolate anion attacks the nitroso group. The rearrangement of semimercaptal needs to be triggered by an acid or hydrated ion (H3O+), which is consistent with the previous assumption. The other pathway, the conversion of semimercaptal to hydroxylamine, has to overcome a higher barrier, although it does not need the participation of an acid or a hydrated ion. In addition, the details on transition states, intermediates and free energy surfaces for three reactions are given, which make up for the lack of experimental knowledge. These conclusions can help to deeply understand the toxic effects of TNT and other nitroaromatic explosives. [ABSTRACT FROM AUTHOR]

Abstract Rapid, reliable, onsite approaches for detection trace level of trinitrotoluene (TNT) is a pressing necessity for both homeland security and environmental protection. To this end, hydrophilic amine(-NH 2) protected Au@Ag nanoparticles (NPs) were developed and fabricated as colorimetric paper sensor for delicate detection of TNT. The as-developed nanoprobe selectively reacts with TNT through classic Meisenheimer complex formation by means of charge transfer process from an electron-rich NH 2 group of β-cysteamine to an electron-deficient nitro group on TNT. Due to the absence of this particular interaction of other nitroaromatics, the proposed probe is highly selective for TNT detection with a better linear range (0–20 μg/mL) and limit of detection (LOD) of 0.35 μg/mL. The present work provides a novel and facile strategy to fabricate colorimetric paper sensors with rapid and selective recognition ability for label free analysis of TNT. Graphical Abstract Unlabelled Image Highlights • A colorimetric paper sensor for delicate detection of TNT using Au@Ag NPs was constructed. • A very low detection limit of around 0.35 μg/mL was achieved. • It is a highly rapid and reliable approach which did not require expensive instruments. [ABSTRACT FROM AUTHOR]

[Display omitted] • A portable testing setup for the detection of trinitrotoluene traces in surfaces by simply using a filter paper and a fluorescent reporter in solution with extreme sensitivity. • A modified Sylgard film useful under real conditions for qualitative fluorescent detection of hidden traces of trinitrotoluene on surfaces or fingers by a swab method. • A combination of quantitative and qualitative detection of trinitrotoluene traces on surfaces as a comprehensive new method for the detection of hidden nitroaromatic explosives in the workplace. We describe the proof of concept of a portable testing setup for the detection of trinitrotoluene (TNT), a common component in hidden explosive devices. The system allows for field-testing and generation of real-time results to test for TNT traces in surfaces by simply using a filter paper and a fluorescent reporter. In this way, the controlled trapping and detection of the analyte by a chemical sensor gives reliable results at extremely low concentrations of TNT on surfaces under real life conditions suitable for daily use in ordinary sampling for example at airlines luggage storage or sport locker rooms. The reported fluorescent methodology is very sensitive and selective, allowing for the trapping and detection of TNT by a fluorescent reporter to give reliable results at very low concentrations. As a complement, we report the preparation of a modified Sylgard film that is useful under real conditions for qualitative fluorescent detection of hidden traces of TNT on surfaces or fingers by a swab method. The combination of quantitative and qualitative detection of TNT traces on surfaces constitutes a comprehensive new method for the detection of hidden nitroaromatic explosives in the workplace. [ABSTRACT FROM AUTHOR]

Crosslinked 2-bromoethyl methacrylate polymer (PBEMA) was prepared in micro-spherical form (2–5 µm) by precipitation polymerization methodology. The bromide substituent was substituted with an azide group, which was then coupled with 1-[(2-Propynyloxy)methyl]pyrene] via alkyne-azide click chemistry. The pyrene-linked microspheres showed an intense green-blue excimer emission with a maximum at 480 nm, implying π−π stacking between the pyrene moieties on the microsphere surfaces. This fluorescence emission is extremely sensitive to the aromatic nitro compounds. So that the green-blue light fades immediately upon addition of trace amounts of 2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (DNT) and 2,4,6-trinitro phenol (TNP) in 100% aqueous media. Stern-Volmer plots were employed for comparison of their fluorescence quenching effects. The plots revealed Stern-Volmer constants of 1.33 × 10 5 , 2.451 × 10 5 and 1.076 × 10 5 M −1 for TNT, TNP and DNT, respectively. Furthermore, it has been observed that, the microspheres can be reused several times, without losing excimer emission properties. [ABSTRACT FROM AUTHOR]

A series of poly(arylene-ethynylene)s (PAEs) containing pentiptycene and t butylpyrene or pyrene in the main chain were synthesized. Introduction of pyrene moiety in the pentiptycene polymeric backbone made the polymers extremely sensitive and selective towards TNT in aqueous solution as well as vapour phase as compared to the other interfering nitroaromatic compounds (NACs) like DNT and PA. In solid state, one of the polymer P2 showed superior sensitivity towards TNT vapours with 60.4% and 90% fluorescence loss within respective 10 s and 30 s of exposure to TNT vapours, which is much higher than most of the reported NACs sensors. Even towards aqueous NACs, the performance of P2 is the best, with 69.8% fluorescence of P2 film getting quenched within 60 s of immersion in aqueous solution of TNT (50 μM). Fluorescence regain study showed that 94% fluorescence is re-gained after dipping the fluorescence-quenched polymer film in methanol for 20 s. The polymers were found to possess high thermal stability (282–585 °C) and appreciably high fluorescence quantum yield (0.39–0.65). We also report the sub-nanoscopic free volume and its distribution in the polymers, as quantified by positron annihilation life time spectroscopy (PALS). [ABSTRACT FROM AUTHOR]

Microbial remediation of nitroaromatic compounds (NACs) is a promising environmentally friendly and cost-effective approach to the removal of these life-threating agents. Escherichia coli (E. coli) has shown remarkable capability for the biotransformation of 2,4,6-trinitro-toluene (TNT). Efforts to develop E. coli as an efficient TNT degrading biocatalyst will benefit from holistic flux-level description of interactions between multiple TNT transforming pathways operating in the strain. To gain such an insight, we extended the genome-scale constraint-based model of E. coli to account for a curated version of major TNT transformation pathways known or evidently hypothesized to be active in E. coli in present of TNT. Using constraint-based analysis (CBA) methods, we then performed several series of in silico experiments to elucidate the contribution of these pathways individually or in combination to the E. coli TNT transformation capacity. Results of our analyses were validated by replicating several experimentally observed TNT degradation phenotypes in E. coli cultures. We further used the extended model to explore the influence of process parameters, including aeration regime, TNT concentration, cell density, and carbon source on TNT degradation efficiency. We also conducted an in silico metabolic engineering study to design a series of E. coli mutants capable of degrading TNT at higher yield compared with the wild-type strain. Our study, therefore, extends the application of CBA to bioremediation of nitroaromatics and demonstrates the usefulness of this approach to inform bioremediation research. [ABSTRACT FROM AUTHOR]

We have prepared four water-soluble poly(p-phenyleneethynylene)s, two of which are novel and carry benzylic side chains that are negatively charged. All of the four PPEs were employed to detect nitroaromatic compounds in water. The two novel PPEs with the benzylic side chains react fairly sensitive toward DNT and TNT in water. If the benzylic side groups are alkoxy-substituted, TNT is detected at concentrations down to 0.27 μM. 12 different nitroaromatics were successfully discriminated by a small array consisting of either two or four of the PPEs and employing linear discriminant analysis. [ABSTRACT FROM AUTHOR]

The authors describe an electrochemiluminescence (ECL) assay for the determination of 2,4,6-trinitrotoluene (TNT) in soil. It is based on the finding that graphene quantum dots (GQDs) strongly enhance the ECL of CdSe quantum dots (CdSe QDs), and ECL is strongly quenched by TNT. In order to assemble the GQDs and CdSe QDs, the latter were functionalized with carboxy groups and then coupled to amino-functionalized GQDs (afGQDs). The resulting CdSe-GQDs conjugation was placed as a thin film on a glassy carbon electrode (GCE). The modified electrode displays an about 8-fold enhanced ECL intensity compared to an GCE with CdSe QDs only, and the onset potential of the ECL reaction is positively shifted by 140 mV. In the presence of TNT, the ECL is quenched due to the formation of the TNT-amine complex. The decrease in ECL intensity is related to the logarithm of the TNT concentration in the range from 0.01 to 100 ppb, with a detection limit as low as 3 ppt. The results of TNT assays in (spiked) soil samples showed recoveries between 99.2 and 105.0 % and relative standard deviations between 3.0 and 8.2 %. This strategy offers a new perspective for developing ECL assays based on the use of semiconductor nanoparticles and graphene-based nanomaterials. [ABSTRACT FROM AUTHOR]

The exploration of feasible, reliable sensors for the selective and sensitive detection of nitroaromatic explosives is a critical issue nowadays as mandated by homeland security concerns. Our endeavor is to develop an instant on-site visual and ultra-sensitive photothermal nanosensor for 2,4,6 -trinitrotoluene (TNT) detection, which could be applied on a broad scale with high selectivity and sensitivity. The fundamental principle of our work is that TNT could effectively induce the aggregation of the cysteamine-stabilized gold nanoparticles (Au NPs) by forming the Meisenheimer complex, which further enhanced the surface plasmon resonance (SPR) properties and the photothermal effects of Au NPs. Other coexisting nitroaromatics have negligible influences on the photothermal responses. By means of the temperature enhancement and photothermal imaging technique, the presence of TNT could be readily recognized and visualized, indicating wide potential applications in analytical sensing. [ABSTRACT FROM AUTHOR]

The explosive power or strength of an energetic material shows its capacity for doing useful work. This work reviews recent developments for prediction of power of energetic compounds. A new user-friendly computer code is also introduced to predict the relative power of a desired energetic compound as compared to 2,4,6-trinitrotoluene (TNT). It is based on the best available methods, which can be used for different types of energetic compounds including nitroaromatics, nitroaliphatics, nitramines, and nitrate esters. The computed relative powers are consistent with the measured data for some new materials containing complex molecular structures. [ABSTRACT FROM AUTHOR]

The tris-Tröger's bases (TBs) are electron-rich fluorescent concave receptors due to the incorporation of naphthalene or triphenylene moieties (calix-1 and calix-2). The structures of the TBs were studied using SXRD to reveal the propensity to bind nitroaromatics. Titration with explosive-related nitro-compounds suggests that the TBs may be used for sensing explosives. [ABSTRACT FROM AUTHOR]

Pyrene-containing water-soluble probes for the fluorescent detection of nitroaromatic compounds (NACs), such as explosive components (2,4-DNT and 2,4,6-TNT) and herbicides (2,4-dinitrocresol, 2,4-DNOC), in aqueous media are reported. In the probes, the introduction of surface-active hydrophilic 'heads' at the periphery of lipophilic (i.e., hydrophobic) pyrene 'tails' resulted in the formation of highly fluorescent micelle-like aggregates/pre-associates in aqueous solutions at concentrations of ≤10−5 m. The enhanced fluorescence quenching of the herein reported architectures is achieved in the presence of ultra-trace amounts of TNT or 2,4-DNT with values of Stern-Volmer quenching constant close to 1×105 m−1 and a detection limit as low as 182 ppb. The most hydrophilic probes demonstrated higher response to 2,4-DNT over TNT. Filter paper test strips impregnated with 1×10−5 m solutions of the probes were able to detect TNT, 2,4-DNT, and other NACs at levels as low as 50 ppb in water. [ABSTRACT FROM AUTHOR]

Picric acid (PA) explosive is a hazard to public safety and health, so the sensitive and selective detection of PA is very important. In the present work, polyethyleneimine stabilized Ag nanoclusters were successfully used for the sensitive and selective quantification of PA on the basis of fluorescence quenching. The quenching efficiency of Ag nanoclusters is proportional to the concentration of PA and the logarithm of PA concentration over two different concentration ranges (1.0 nM–1 μM for the former and 0.25–20 μM for the latter), thus the proposed quantitative strategy for PA provides a wide linear range of 1.0 nM–20 μM. The detection limit based on 3σ/K is 0.1 nM. The quenching mechanism of Ag nanoclusters by PA is discussed in detail. The results indicate that the selective detection of PA over other nitroaromatics including 2,4,6-trinitrotoluene (TNT), 2,4-dinitrotoluene (2,4-DNT), p-nitrotoluene (p-NT), m-dinitrobenzene (m-DNB), and nitrobenzene (NB), is due to the electron transfer and energy transfer between PA and polyethyleneimine-capped Ag nanoclusters. In addition, the experimental data obtained for the analysis of artificial samples show that the proposed PA sensor is potentially applicable in the determination of trace PA explosive in real samples. [ABSTRACT FROM AUTHOR]

The detection of explosives is one of the current pressing concerns in global security. In the past few decades, a large number of emissive sensing materials have been developed for the detection of explosives in vapor, solution, and solid states through fluorescence methods. In recent years, great efforts have been devoted to develop new fluorescent materials with various sensing mechanisms for detecting explosives in order to achieve super-sensitivity, ultra-selectivity, as well as fast response time. This review article starts with a brief introduction on various sensing mechanisms for fluorescence based explosive detection, and then summarizes in an exhaustive and systematic way the state-of-the-art of fluorescent materials for explosive detection with a focus on the research in the recent 5 years. A wide range of fluorescent materials, such as conjugated polymers, small fluorophores, supramolecular systems, bio-inspired materials and aggregation induced emission-active materials, and their sensing performance and sensing mechanism are the centerpiece of this review. Finally, conclusions and future outlook are presented and discussed. [ABSTRACT FROM AUTHOR]

The current study aims to characterize and evaluate the photocatalytic treatability of the “red water” effluent from a Brazilian TNT production industry. Analyses were performed using physical, chemical, spectroscopic and chromatographic assays, which demonstrated that the effluent presented a significant pollution potential, mainly due to COD, BOD, solids and to the high concentration of nitroaromatic compounds such as 1,3,5-trinitrobenzene, 1-methyl-2,4-dinitrobenzene, 2-methyl-1,3-dinitrobenzene, 2,4,6-trinitrotoluene-3,5-dinitro- p -toluidine and 2-methyl-3,5-dinitro-benzoamine. By a modified sol-gel and a dip-coating technique, it was possible to obtain a TiO 2 film on borosilicate glass substrate which functional composition and microstructure were characterized by infrared spectroscopy and scanning electron microscopy. The evaluation of the photocatalytic treatability using borosilicate-glass-TiO 2 demonstrated high degradation efficiency. In this context, a reduction of 32 and 100% for COD and nitroaromatic compounds, respectively, was observed. Although the proposed photocatalytic process has found difficulties in reducing the content of organic matter and effluent color in the red water, its potential for degrading refractory chemical compounds such as the nitroaromatic ones enables it to be used as tertiary treatment. [ABSTRACT FROM AUTHOR]

The rapid detection of nitroaromatic explosive in low concentration sample or complex matrices is of importance. In this paper, 2,4,6-trinitrotoluene (TNT) molecularly imprinted polyvinyl alcohol microspheres, MIP-CPVA, are synthesized in inverse suspension system using TNT as template, PVA as functional polymer, and glutaraldehyde as cross-linker. The MIP-CPVA possesses high affinity, specific recognition ability, and excellent selectivity towards TNT. The saturated adsorption capacity could reach to 10.62 mg g−1, and the selectivity coefficients relative to DNT is 12.44. In additional, MIP-CPVA can be used as the column packing of gas chromatograph to separate and detect nitroaromatic, and the result is very satisfactory. [ABSTRACT FROM PUBLISHER]

We report for the first time a photothermal paper sensor for the selective and sensitive detection of 2,4,6-trinitrotoluene (TNT) down to 14 ng/cm2. In the presence of TNT, a Meisenheimer complex was formed by means of a charge transfer process from an electron-rich group in polyaniline (PANI) to an electron-deficient nitro group in TNT, which resulted in the near-infrared absorption around 800 nm. Upon irradiation with an 808 nm diode laser, the photothermal effect of the PANI/TNT complex caused the temperature increase, and the temperature difference (ΔT) was proportional to the TNT concentration, while the temperature increase was hardly observed for other nitroaromatics including 2,4-dinitrotoluene (DNT), 2,4,6-trinitrophenol (TNP), and nitrobenzene (NB), affording high selectivity toward TNT. All the tests can be conducted both in solution and on paper. Therefore, the proposed photothermal strategy not only offers a fast and convenient protocol for selective detection of TNT but also indicates great potential in practical applications, especially for airport/railway security inspection and prevention of terrorist attacks. [ABSTRACT FROM AUTHOR]

Efficient sensing of trace amount nitroaromatic (NAC) explosives has become a major research focus in recent time due to concerns over national security as well as their role as environment pollutants. NO2-containing electron-deficient aromatic compounds, such as picric acid (PA), trinitrotoluene (TNT), and dinitrotoluene (DNT), are the common constituents of many commercially available chemical explosives. In this article, we have summarized our recent developments on the rational design of electron-rich self-assembled discrete molecular sensors and their efficacy in sensing nitroaromatics both in solution as well as in vapor phase. Several π-electron-rich fluorescent metallacycles (squares, rectangles, and tweezers/pincers) and metallacages (trigonal and tetragonal prisms) have been synthesized by means of metal-ligand coordination-bonding interactions, with enough internal space to accommodate electron-deficient nitroaromatics at the molecular level by multiple supramolecular interactions. Such interactions subsequently result in the detectable fluorescence quenching of sensors even in the presence of trace quantities of nitroaromatics. The fascinating sensing characteristics of molecular architectures discussed in this article may enable future development of improved sensors for nitroaromatic explosives. [ABSTRACT FROM AUTHOR]

Sensitive optical detection of nitroaromatic vapours with diketopyrrolopyrrole thin films is reported for the first time and the impact of thin film crystal structure and morphology on fluorescence quenching behaviour demonstrated. [ABSTRACT FROM AUTHOR]

Polyurea dendrimer-perylene nanoshells are found to accurately discriminate structurally closely related nitroaromatics. Both studied systems, PUREG1-PER6 and PUREG4-PER48, present high sensitivity (detection limits between 5 × 10−6 and 20 × 10−6 m) and selectivity for 2,4,6-trinitrotoluene (TNT) collected from a powdered military grenade and picric acid. The selectivity is highly dependent on the dendrimer generation. A conformationally restricted 3D arrangement in PUREG4-PER48, which is favored by shell π-π stacking and core urea-assisted hydrogen bonding, supports the formation of self-imprinted channels with molecular recognition for picric acid and TNT in complex mixtures of nitroaromatics. [ABSTRACT FROM AUTHOR]

Tetraphenylethylene pillar[6]arenes with an AIE effect were synthesized for the first time. The fluorescence of the pillar[6]arenes could be quenched much more and much faster by TNT than by other nitroaromatics including 2,4,6-trinitrophenol, which could be used to detect TNT in air. [ABSTRACT FROM AUTHOR]

A new class of dual fluorescent chemosensors for nitroaromatic compounds (NACs) based on phosphonated pyrene derivatives is reported, showing high selectivity towards trinitrotoluene (TNT). The strong intermolecular interactions (π- π stacking and hydrogen bonding) allow high fluorescence quenching with visual detection in short response times. [ABSTRACT FROM AUTHOR]

Instant detection of trace-level nitroaromatic explosives is highly desirable for national security and environmental protection. In this paper, a new strategy for the construction of nitroaromatic-indicator paper was proposed based on a mixture of red emitting cysteamine modified cadmium telluride quantum dots and green emitting thioglycollic acid capped cadmium telluride quantum dots which served as the nitroaromatic sensor and reference probes, respectively. Nitroaromatic-indicator paper showed excellent response to trinitrotoluene and picric acid with visual detection limits of 1.59 and 1.16 ng mm−2. The screening process was accomplished within half a minute. The visualization of the nitroaromatic-indicating paper was significantly enhanced when the green reference probe was used as the background. Therefore, a rapid, simple, convenient, and high selectivity paper sensor was developed for nitroaromatics. [ABSTRACT FROM AUTHOR]

Abstract: A series of poly(arylene ethynylene)s (PAEs) containing t butyl pyrene in the main chain were synthesized for nitroaromatic sensors. As control, similar polymers containing unsubstituted pyrene were also synthesized. The sensory properties of the polymers were studied towards various nitroaromatic compounds like trinitrotoluene (TNT), dinitrotoluene (DNT), nitrotoluene (NT), nitrobenzene (NB) and picric acid (PA) in solution as well as vapor state. Interestingly, all the t butyl substituted pyrene containing polymers showed higher sensitivity than the corresponding unsubstituted pyrene containing polymers. Moreover, the polymers showed high sensitivity towards TNT as compared to the other nitroaromatic compounds. The sensitivity of one of the polymer PB was found several folds higher than that of the similar reported polymer containing unsubstituted pyrene ring. In addition, t butyl pyrene containing polymers were found to have improved molecular weight, thermal stability, fluorescence quantum yield, film forming properties and solubility in common organic solvents as compared to the control polymers. [Copyright &y& Elsevier]

ABSTRACT A series of eight poly( p-phenylene vinylene) (PPV) and poly( p-phenylene ethynylene) (PPE) ( P1-P8) derivatives were tested for their ability to detect the nitroaromatic explosive 2,4,6-trinitrotoluene (TNT) and its model compound 2,6-dinitrotoluene (DNT). The polymers P1-P8 represent five structural classes that have not been examined for nitroaromatic sensing. These new motifs include PPE derivatives with a main-chain m-terphenyl unit ( P1) or oxacyclophane canopy-like structure ( P2) and PPV derivatives with 2,6-mesitylenephenylene repeats ( P3 and P4), 9,9-dialkyl-1,4-fluorenylene repeats ( P5 and P6), or m-phenylene units that periodically disrupt π-conjugation along the backbone of the polymer ( P7 and P8). The time-dependent photoluminescent response of films to TNT and DNT and the solution-phase Stern-Volmer quenching constants for both TNT and DNT were determined. The results are rationalized in terms of side-chain sterics and π-system electronics and are discussed relative to known conjugated polymers. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 1487-1492 [ABSTRACT FROM AUTHOR]

2,4,6-Trinitrotoluene (TNT) is a widely used nitroaromatic explosive with significant detrimental effects on the environment and human health. Its detection is of great importance. In this study, both electrochemiluminescence (ECL)-based detection of TNT through the formation of a TNT-amine complex and the detection of TNT through electrochemiluminescence resonance energy transfer (ECRET) are developed for the first time. 3-Aminopropyltriethoxysilane (APTES)-modified [Ru(phen)3]2+ (phen=1,10-phenanthroline)-doped silica nanoparticles (RuSiNPs) with uniform sizes of (73±3) nm were synthesized. TNT can interact with APTES-modified RuSiNPs through charge transfer from electron-rich amines in the RuSiNPs to the electron-deficient aromatic ring of TNT to form a red TNT-amine complex. The absorption spectrum of this complex overlaps with the ECL spectrum of the APTES-modified RuSiNPs/triethylamine system. As a result, ECL signals of the APTES-modified RuSiNPs/triethylamine system are turned off in the presence of TNT owing to resonance energy transfer from electrochemically excited RuSiNPs to the TNT-amine complex. This ECRET method has been successfully applied for the sensitive determination of TNT with a linear range from 1×10−9 to 1×10−6 M with a fast response time within 1 min. The limit of detection is 0.3 n M. The method exhibits good selectivity towards 2,4-dinitrotoluene, p-nitrotoluene, nitrobenzene, phenol, p-quinone, 8-hydroxyquinoline, p-phenylenediamine, K3[Fe(CN)6], Fe3+, NO3−, NO2−, Cr3+, Fe2+, Pb2+, SO32−, formaldehyde, oxalate, proline, and glycine. [ABSTRACT FROM AUTHOR]

Abstract: This paper reports a rapid, sensitive, and selective nanosensor for the detection of 2,4,6-trinitrotoluene (TNT) in the mixture aqueous solution of nitroaromatics independent of immunoassay or molecularly imprinted technology and complicated instruments. Despite many strategies including immunoassay and molecularly imprinted technologies been successfully developed for the detection of TNT, it is not easy to differentiate TNT from 2,4,6-trinitrophenol (TNP) due to their very similar chemical structures and properties. In this work, the amine functionalized NaYF4:Yb3+/Er3+ upconversion luminescence nanoparticles (UCNPs) whose excitation (980nm) and emission (543nm) wavelength were far from the absorbance bands of other usual interference nitroaromatics including 2,4-dinitrotoluene (DNT), nitrobenzene (NB), and especially TNP, were utilized as the luminescent nanosensors for TNT luminescence detection. To make these UCNPs highly water stable and render the charge transfer from UCNPs to TNT easier, amino groups were introduced onto the surface of the UCNPs by coating a polymer layer of ethylene glycol dimethacrylate (EGDMA) hybridized with 3-aminopropyltriethoxysilane (APTS). After binding with TNT through amino groups on the UCNPs, the naked eye visible green upconversion luminescence of the UCNPs was dramatically quenched and thus a sensitive UC luminescence nanosensor was developed for TNT detection. However, other nitroaromatics including TNP, DNT, and NB have no influence on the green UC luminescence and thus no influence on the TNT detection. The luminescence intensity is negatively proportional to the concentration of TNT in the range of 0.01−9.0µg/mL with the 3σ limit of detection (LOD) of 9.7ng/mL. The present studies provide a novel and facile strategy to fabricate the upconversion luminescence sensors with highly selective recognition ability in aqueous media and are desirable for label free analysis of TNT in mixed solution independent of immunoassay and molecularly imprinted technology and complicated instruments. [Copyright &y& Elsevier]

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. [ABSTRACT FROM AUTHOR]

Abstract: Rapid, sensitive and selective detection of 2,4,6-trinitrotoluene (TNT) in aqueous solution differentiating from other nitroaromatics and independent of complicated instruments is in high demand for public safety and environmental monitoring. Despite of many methods for TNT detection, it is hard to differentiate TNT from 2,4,6-trinitrophenol (TNP) due to their highly similar structures and properties. In this work, via a simple and versatile method, LaF3ːCe3+−Tb3+and Fe3O4 nanoparticle-codoped multifunctional nanospheres were prepared through self-assembly of the building blocks. The luminescence of these nanocomposites was dramatically quenched via adding nitroaromatics into the aqueous solution. After the magnetic separation, however, the interference of other nitroaromatics including 2,4,6-trinitrophenol (TNP), 2,4-dinitrotoluene (DNT), and nitrobenzene (NB) was effectively overcome due to the removal of these coexisting nitroaromatics from the surface of nanocomposites. Due to the formation of TNT−−RCONH3 +, the TNT was attached to the surface of the nanocomposites and was quantitatively detected by the postexposure luminescence quenching. Meanwhile, the luminescence intensity is negatively proportional to the concentration of TNT in the range of 0.01–5.0μg/mL with the 3σ limit of detection (LOD) of 10.2ng/mL. Therefore, the as-developed method provides a novel strategy for rapid and selective detection of TNT in the mixture solution of nitroaromatics by postexposure luminescence quenching. [Copyright &y& Elsevier]

We report first-principles calculations of the adsorption of 2,4,6-trinitrotoluene (TNT), a prototypical nitroaromatic explosive, on the ZnO ([formula]) surface. This surface is common among ZnO chemiresistors being considered for trace explosive detection. Recent work has achieved 60 ppb detection of TNT using a ZnO nanowire array, but the physical mechanism of sensing is unclear. Our results indicate that TNT strongly chemisorbs via interactions between the oxygen on the nitro groups and surface zinc, creating surface states within the gap. We present a theoretical estimate showing the strong effect of these surface states on the depletion layer of ZnO nanowires. [ABSTRACT FROM AUTHOR]

ABSTRACT Reported herein is the highly efficient quenching of fluorescent organic nanoparticles by 2,4-dinitrotoluene and 2,4,6-trinitrotoluene. These fluorescent nanoparticles are formed from the hydrophobic collapse of fluorescent polymer chains and display quenching efficiencies that are in line with the highest reported literature values. Moreover, the fluorescent quenching occurs only for the fluorescent nanoparticles, and not for the precursor polymer solutions, which display marked insensitivity to the presence of nitroaromatics. This aggregation-dependent fluorescent quenching has numerous applications for the detection of small-molecule electron-deficient analytes. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4150-4155 [ABSTRACT FROM AUTHOR]

Nowadays, the ballistic mortar is the preferred test for the explosive power measurements but there is no reliable method for its prediction. For an energetic compound, the formation of low molecular mass gaseous products and a high positive heat of formation per unit weight of the energetic compound are important parameters to have a high value of power. A novel method was developed to predict the power by the ballistic mortar test for pure and mixture of energetic materials. It can be used for some important classes of energetic compounds including nitroaromatics, acyclic and cyclic nitramines, nitrate esters, and nitroaliphatics. The presented method is based on the molecular structure of the desired compound and there is no need to use experimental data such as the condensed phase heat of formation. For 84 pure and 24 mixtures of energetic compounds, the calculated power relative to 2,4,6-trinitrotoluene (= 100) show good agreement with respect to the measured values. [ABSTRACT FROM AUTHOR]

Highlights: [•] Sediments dramatically increase removal kinetics of dissolved RDX and TNT. [•] Removal rates very widely among published studies due to experimental setups. [•] Sediment characteristics are proxies for explosive contamination persistence. [Copyright &y& Elsevier]

The environmental impacts of energetic compounds can be minimized through the design and selection of new energetic materials with favorable fate properties. Building predictive models to inform this process, however, is difficult because of uncertainties and complexities in some major fate-determining transformation reactions such as the alkaline hydrolysis of energetic nitroaromatic compounds (NACs). Prior work on the mechanisms of the reaction between NACs and OH- has yielded inconsistent results. In this study, the alkaline hydrolysis of 2,4,6-trinitrotoluene (TNT) and 2,4-dinitroanisole (DNAN) was investigated with coordinated experimental kinetic measurements and molecular modeling calculations. For TNT, the results suggest reversible formation of an initial product, which is likely either a Meisenheimer complex or a TNT anion formed by abstraction of a methyl proton by OH-. For DNAN, the results suggest that a Meisenheimer complex is an intermediate in the formation of 2,4-dinitrophenolate. Despite these advances, the remaining uncertainties in the mechanisms of these reactions-and potential variability between the hydrolysis mechanisms for different NACs-mean that it is not yet possible to generalize the results into predictive models (e.g., quantitative structure-activity relationships, QSARs) for hydrolysis of other NACs. [ABSTRACT FROM AUTHOR]

The feasibility of using nanoscale zerovalent iron (nZVI) treatment for reducing the acute toxicity of explosive wastewater, such as 2,4,6-trinitrotoluene (TNT) red water which contains highly toxic nitroaromatic compounds (NACs), has been investigated. The water quality was evaluated before and after nZVI treatment using several different analytical techniques, including UV-Vis spectroscopy, X-ray photoelectron spectroscopy, high-performance liquid chromatography, and gas chromatography/mass spectroscopy. The acute toxicity of the wastewater was tested using a luminescence bacterium bioarray. The results indicated that the most significant toxic NACs, such as dinitrotoluene sulfonates, had been effectively removed from the TNT red water by nZVI together with the small amounts of other NACs. Following 1 h of the nZVI processing treatment, the acute toxicity of the TNT wastewater was reduced by approximately 94 %. This treatment would therefore be useful for the pretreatment of wastewaters prior to the application of a biological process. The reduction in the biotoxicity of the wastewater was based on the reductive conversion processes and adsorption behaviors of nZVI. [ABSTRACT FROM AUTHOR]

2,4-Dinitroanisole (DNAN) is a low sensitive melt-cast chemical being tested by the Military Industry as a replacement for 2,4,6-trinitrotoluene (TNT) in explosive formulations. Little is known about the fate of DNAN and its transformation products in the natural environment. Here we report aerobic biotransformation of DNAN in artificially contaminated soil microcosms. DNAN was completely transformed in 8 days in soil slurries supplemented with carbon and nitrogen sources. DNAN was completely transformed in 34 days in slurries supplemented with carbons alone and persisted in unamended microcosms. A strain of Bacillus (named 13G) that transformed DNAN by co-metabolism was isolated from the soil. HPLC and LC-MS analyses of cell-free and resting cell assays of Bacillus 13G with DNAN showed the formation of 2-amino-4-nitroanisole as the major end-product via the intermediary formation of the arylnitroso (ArNO) and arylhydroxylamino (ArNHOH) derivatives, indicating regioselective reduction of the ortho-nitro group. A series of secondary reactions involving ArNO and ArNHOH gave the corresponding azoxy- and azo-dimers. Acetylated and demethylated products were identified. Overall, this paper provides the evidence of fast DNAN transformation by the indigenous microbial populations of an amended soil with no history of contamination with explosives and a first insight into the aerobic metabolism of DNAN by the soil isolate Bacillus 13G. [ABSTRACT FROM AUTHOR]

Abstract: Molecular modeling techniques were employed to study the interaction of trinitrotoluene with an amplifying fluorescent polymer used in explosive sensor devices. The pentiptycene moiety present in these polymers appears to be the most energetically favorable binding site for trinitrotoluene. Surface features of the polymer suggest that the small cavity feature of the pentiptycene moiety may be more available for binding to analyte compounds due to steric crowding about the large cavity. Binding energies between model binding sites of the polymer and various analyte compounds were more rigorously estimated by semiempirical and ab initio techniques. Binding energies were found to be largest with trinitrotoluene and other nitroaromatic compounds. Electrostatic and π-stacking interactions between trinitrotoluene and the model host were investigated by studying a series of modified host compounds. [Copyright &y& Elsevier]

Abstract: This study is primarily focused in establishing the solid-state sensory abilities of several luminescent polymeric calix[4]arene-based materials toward selected nitroaromatic compounds (NACs), creating the foundations for their future application as high performance materials for detection of high explosives. The phenylene ethynylene-type polymers possessing bis-calix[4]arene scaffolds in their core were designed to take advantage of the known recognition abilities of calixarene compounds toward neutral guests, particularly in solid-state, therefore providing enhanced sensitivity and selectivity in the sensing of a given analyte. It was found that all the calix[4]arene-poly(para-phenylene ethynylene)s here reported displayed high sensitivities toward the detection of nitrobenzene, 2,4-dinitrotoluene and 2,4,6-trinitrotoluene (TNT). Particularly effective and significant was the response of the films (25–60nm of thickness) upon exposure to TNT vapor (10ppb): over 50% of fluorescence quenching was achieved in only 10s. In contrast, a model polymer lacking the calixarene units showed only reduced quenching activity for the same set of analytes, clearly highlighting the relevance of the macrocyclics in promoting the signaling of the transduction event. The films exhibited high photostability (less than 0.5% loss of fluorescence intensity up to 15min of continuous irradiation) and the fluorescence quenching sensitivity could be fully recovered after exposure of the quenched films to saturated vapors of hydrazine (the initial fluorescence intensities were usually recovered within 2–5min of exposure to hydrazine). [Copyright &y& Elsevier]

Abstract: Rapid and inexpensive sensing of explosive traces in soil and post-blast debris for environmental and criminological purposes with optical sensors has recently gained importance. The developed sensing method for nitro-aromatic and nitramine-based explosives is based on dropping an acetone solution of the analyte to an adsorbent surface, letting the solvent to dry, spraying an analytical reagent to produce a persistent spot, and indirectly measuring its reflectance by means of a miniature spectrometer. This method proved to be useful for on-site determination of nitro-aromatics (trinitrotoluene (TNT), 2,4,6-trinitrophenylmethylnitramine (tetryl) and dinitrotoluene (DNT)) and nitramines (1,3,5-trinitro-1,3,5-triazacyclohexane (RDX) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX)) pre-adsorbed on a poly vinyl chloride (PVC) surface, with the use of different spray reagents for each group of explosives producing different colors. The calibration equations of the tested compounds as reflectance vs. concentration showed excellent linearity (correlation coefficient: 0.998–0.999). The linear quantification interval in terms of absolute quantity of analyte was 0.1–0.5μg. The developed method was successfully tested for the analysis of military explosives Comp B and Octol, and was validated against high performance liquid chromatography (HPLC). The reflectometric sensing method could also be used for qualitative identification of the nitrated explosives on a chromatographic paper. The reagent-impregnated paper could also serve as sensor, enabling semi-quantitative determinations of TNT and tetryl. [Copyright &y& Elsevier]

Abstract: In this work, we demonstrated a sensitive and selective electrochemical sensing protocol for the detection of TNT prepared from alkanethiols self-assembled on AuNPs modified glassy carbon (GC) electrode with preadsorbed templates of TNT. It demonstrated that the 2D molecular imprinting monolayers (MIMs) can provide a better site accessibility and lower mass-transfer resistance, while the AuNPs can enhance electrode conductivity, facilitate the electron transfer and increase the amount of TNT-imprinted sites. The prepared sensor showed not only high selectivity toward TNT in comparison to other similar nitroaromatic compounds (NACs), but also a wide linear range over TNT concentration from 4.0×10−8 to 3.2×10−6 M with a detection limit of 1.3×10−8 M (S/N=3). Moreover, the imprinted sensor has been applied to the determination of TNT in spiked environmental water samples and shows promise for fast and sensitive measurement of trace levels of TNT in real samples. [Copyright &y& Elsevier]

Abstract: This study aims to provide simple but reliable theoretical model for monomer selection for molecular imprinting towards detection of nitroaromatic compounds. Presented data show that molecular imprinted polymer/non-imprinted polymer (MIP/NIP) system can be characterized sufficiently by use of very simple model. This model provides detailed description (qualitative and quantitative) regarding hydrogen bonding between the template and polymeric matrix hence can become good theoretical tool for monomer selection. Ab initio DFT (Density Functional Theory) method has been applied for structural, solvent, and vibrational frequency calculations. Binding energy and IR spectra have been carefully evaluated. Additionally, experimental FT-IR spectroscopy has been conducted to validate the formation of hydrogen bonding between studied species. [Copyright &y& Elsevier]

We have investigated a series of branched fluorescent sensing compounds with thiophene units in the arms and triphenylamine centers for the detection of nitrated model compounds for 2,4,6-trinitrotoluene (TNT) and the plastic explosives taggant 2,3-dimethyl-2,3-dinitrobutane (DMNB). Stern−Volmer measurements in solution show that the fluorescence is more efficiently quenched by nitroaromatic compounds when compared to a non-nitrated quencher, benzophenone. Simple modification of the structure of the sensing compound was found to result in significant changes to the sensitivity and selectivity toward the nitrated analytes. A key result from time-resolved fluorescent measurements showed that the chromophore−analyte interaction was primarily a collisional process. This process is in contrast to conjugated polymers where static quenching dominates, a difference that could offer a potentially more powerful detection mechanism. [ABSTRACT FROM AUTHOR]

The morphology of glassy carbon surfaces was investigated by the atomic force microscope (AFM) method. Multi-wall carbon nanotubes (MWCNTs) were purified and investigated with a scanning electron microscope (SEM) and a transmission electron microscope (TEM). An electrochemical technique based on the glassy carbon electrode (GCE) or MWCNT-modified GCEs was used for the detection of nitroaromatic compounds (NACs), namely 2,4,6-trinitrotoluene (TNT), 1,3,5-trinitrobenzene (TNB), 2,4-dinitrotoluene (2,4-DNT), and 1,3-dinitrobenzene (1,3-DNB). MWCNT-modified GCEs were more sensitive than GCEs to TNB, 2,4-DNT, and 1,3-DNB, with the detection limit down to ppb level, whereas the modified GCEs showed lower sensitivity to TNT. In varying degrees, the accumulation of nitro compounds can be promoted by MWCNT-modified GCEs in the detection process, a property which can be attributed to the large surface area and graphene-sheet structure of MWCNTs. [ABSTRACT FROM AUTHOR]