Explosive Trinitrotoluene Research Articles

TAML Activator/Peroxide-Catalyzed Facile Oxidative Degradation of the Persistent Explosives Trinitrotoluene and Trinitrobenzene in Micellar Solutions

TAML activators are well-known for their ability to activate hydrogen peroxide to oxidize persistent pollutants in water. The trinitroaromatic explosives, 2,4,6-trinitrotoluene (TNT) and 1,3,5-trinitrobenzene (TNB), are often encountered together as persistent, toxic pollutants. Here we show that an aggressive TAML activator with peroxides boosts the effectiveness of the known surfactant/base promoted breakdown of TNT and transforms the surfactant induced nondestructive binding of base to TNB into an extensive multistep degradation process. Treatment of basic cationic surfactant solutions of either TNT or TNB with TAML/peroxide (hydrogen peroxide and tert-butylhydroperoxide, TBHP) gave complete pollutant removal for both in <1 h with >75% of the nitrogen and ≥20% of the carbon converted to nitrite/nitrate and formate, respectively. For TNT, the TAML advantage is to advance the process toward mineralization. Basic surfactant solutions of TNB gave the colored solutions typical of known Meisenheimer complexes which did not progress to degradation products over many hours. However with added TAML activator, the color was bleached quickly and the TNB starting compound was degraded extensively toward minerals within an hour. A slower surfactant-free TAML activator/peroxide process also degrades TNT/TNB effectively. Thus, TAML/peroxide amplification effectively advances TNT and TNB water treatment giving reason to explore the environmental applicability of the approach.

Hybrid preconcentrator/focuser module for determinations of explosive marker compounds with a micro-scale gas chromatograph

This article describes the development and characterization of a partially selective preconcentrator/focuser (PCF) module for a field-portable micro-scale gas chromatograph (μGC) designed to rapidly determine trace levels of two vapor-phase markers of the explosive trinitrotoluene (TNT): 2,3-dimethyl-2,3-dinitrobutane (DMNB) and 2,4-dinitrotoluene (2,4-DNT). The PCF module has three primary components. The first is a high-volume sampler, comprising a resistively-heated 6-cm long stainless steel tube packed with tandem beds of the graphitized carbons Carbopack B (C-B, 30mg) and Carbopack Y (C-Y, 15mg), which traps the markers but permits more volatile interferences to pass through largely unretained. The second component is a microfocuser (μF), comprising a 4.2×9.8mm Si chip containing a deep-reactive-ion-etched (DRIE) cavity packed with 2mg of C-B, a Pyrex cap, integrated heaters, and etched fluidic channels. The third component is a commercial polymer-membrane filter used as a pre-trap to remove particles and adsorbed low volatility interferences. Markers captured in the sampler are thermally desorbed and transferred to the μF, and then thermally desorbed/injected from the μF into a downstream separation (micro)column and detected. Scrubbed ambient air is used as carrier gas. The adsorbent capacities, baseline temperatures, sampling and desorption flow rates, and heating profiles were optimized for each PCF module component while minimizing the analysis time. An overall transfer efficiency of 86% was achieved at marker concentrations of ∼0.2–2.6ppb. In the final configuration the PCF module requires just 60s to collect a 1-L sample (3L/min), focus (40mL/min), and inject the markers (3mL/min), producing half-maximum injection peak widths of ∼2 and 5s, and preconcentration factors of 4500 and 1800, for DMNB and 2,4-DNT, respectively.

A nanoparticle-coated chemiresistor array as a microscale gas chromatograph detector for explosive marker compounds: flow rate and temperature effects

The effects of flow rate and temperature on the performance of a microscale gas chromatographic (μGC) detector consisting of a chemiresistor (CR) array coated with different thiolate-monolayer-protected gold nanoparticles (MPNs) are described with respect to the analysis of three gas-phase markers of the explosive trinitrotoluene (TNT): 2,4-dinitrotoluene (2,4-DNT), 2,6-dinitrotoluene (2,6-DNT), and 2,3-dimethyl-2,3-dinitrobutane (DMNB). In chamber tests, sensors were stable at 70 °C for several days in air, with <2% sensitivity drift per day and virtually no change in the array response patterns. In tests with a conventional upstream GC column, increasing the array temperature from 55-80 °C (1.2 mL min(-1)) led to similar (i.e., 4-6.6-fold) decreases in sensitivity, increases in the limits of detection (LODs), and increases in (estimated) chromatographic resolution. Increasing the flow rate from 1.1-3.7 mL min(-1) (70 °C) led to ∼1.3-2-fold decreases in sensitivity and LOD for 2,4-DNT and 2,6-DNT, a ∼2-fold net increase in LOD for DMNB (passes through a maximum), and a <2-fold increase in resolution. Results indicate that the rates of desorption of the marker vapors out of the MPN films are important determinants of observed trends. With Si-micromachined focuser/injector and separation column devices placed upstream of a CR array held at 70 °C, a mixture of the two primary markers, 2,4-DNT and DMNB, and four similarly volatile alkane interferents was separated in 1.5 min at 3 mL min(-1).

Disposable screen-printed sensors for the electrochemical detection of TNT and DNT

Due to the heightened level of national security currently prevalent due to the possibility of terrorist incidents, highly portable, miniaturised and sensitive monitoring devices for trace levels of injurious materials, such as explosives are now of the upmost importance. One method that offers a possible route for the development of a detection system for such species is via an electrochemical regime, coupled to the use of disposable sensor technology. Within this study, the use of carbon screen-printed sensors for the detection and analysis of the classical explosive trinitrotoluene (TNT) and the related dinitrotoluene (DNT) is described, with the eventual objective to develop an inexpensive, accurate and sensitive detection system for trace quantities of explosives in field settings. Commercially available screen-printed carbon sensors have been used as the base platform for this investigation and the electrochemistry of both TNT and DNT studied at these surfaces. Two reductive peaks and one oxidative peak were observed for both analytes. The best linear fits and sensitivities were obtained using the reductive peak at -0.72 V vs. Ag/AgCl. A linear range from 1 to 200 μM could be obtained for TNT and DNT in pH 7.0 phosphate buffer with limits of detection as low as 0.4 μM (TNT) and 0.7 μM (DNT). A second system which utilised the addition of the enzyme, nitroreductase, and the coenzyme, NADPH, into the solution matrix prior to electrochemical interrogations with screen-printed carbon electrodes was found to increase the resulting signal magnitude at the oxidation peak at +0.3 V, improving the performance of the sensor at these values.

Crosstalk between endogenous and synthetic components – synthetic signaling meets endogenous components

Synthetic biology uses biological components to engineer new functionality in living organisms. We have used the tools of synthetic biology to engineer detector plants that can sense man-made chemicals, such as the explosive trinitrotoluene, and induce a response detectable by eye or instrumentation. A goal of this type of work is to make the designed system orthogonal, that is, able to function independently of systems in the host. In this review, the design and function of two partially synthetic signaling pathways for use in plants is discussed. We describe observed interactions (crosstalk) with endogenous signaling components. This crosstalk can be beneficial, allowing the creation of hybrid synthetic/endogenous signaling pathways, or detrimental, resulting in system noise and/or false positives. Current approaches in the field of synthetic biology applicable to the design of orthogonal signaling systems, including the design of synthetic components, partially synthetic systems that utilize crosstalk to signal through endogenous components, computational redesign of proteins, and the use of heterologous components, are discussed.

Gorlovka Chemical Plant: Addressing a Piece of the Toxic Soviet Legacy

Background. The Gorlovka chemical plant is an abandoned industrial complex in the Donetsk region of Ukraine. The facility produced toxic mononitrochlorobenzene (MNCB) and explosive trinitrotoluene (TNT) until it was abruptly abandoned in 2001. The plant is now the subject of a cleanup project coordinated by a broad group of stakeholders, including the government of Ukraine, regional and municipal authorities, the international not-for-profit Blacksmith Institute, institutional and private sector donors, and local contractors. Objectives. Remediation efforts at the Gorlovka chemical plant complex aim to reduce environmental health risks to the local community by removing remaining stocks of MNCB and TNT, and analyzing soil and groundwater for potential contamination. Discussion. The Gorlovka Chemical Plant is one of many toxic sites left from Soviet industrial activities. Throughout Russia, Eastern Europe and Central Asia, former Soviet states are discovering and trying to deal with polluted sites that pos...

Trinitrotoluene Explosive Lights up Ultrahigh Raman Scattering of Nonresonant Molecule on a Top-Closed Silver Nanotube Array

The highest Raman enhancement factors are obtained in a double resonance: molecular electronic resonance and plasmon resonance with a "hot spot" in surface-enhanced Raman scattering (SERS). However, for most molecules of interest the double resonance is not realized with the excitation frequencies normally used in Raman. The latter may limit the practical applications of SERS for trace analysis. Here, we report that Raman-inactive trinitrotoluene (TNT) lights up the ultrahigh Raman scattering of off-resonated p-aminobenzenethiol (PABT) through the formation of charge-transfer TNT-PABT complex on the top-closed flexible silver nanotube array. Raman hot spots can spontaneously form in a reversible way by the self-approaching of flexible nanotubes driven through the capillary force of solvent evaporation. Meanwhile, the PABT-TNT-PABT bridges between self-approaching silver nanotubes possibly form by the specific complexing and zwitterion interactions, and the resultant chromophores can absorb the visible light that matches with the incident laser and the localized surface plasmon of a silver nanotube array. The multiple spectral resonances lead to the huge enhancement of Raman signals of PABT molecules due to the presence of ultratrace TNT. The enhancement effect is repeatedly renewable by the reconstruction of molecular bridges and can selectively detect TNT with a limit of 1.5 × 10(-17) M. The results in this report provide the simple and supersensitive approach to the detection of TNT explosives and the possibility of building a robust Raman-based assay platform.

Computational study of the catalytic effect of platinum on the decomposition of DNT

AbstractThe catalytic decomposition of dinitrotoluene (DNT; 3‐4‐DNT), a by‐product of the explosive trinitrotoluene (trotyl), on a platinum surface is investigated computationally. Reaction paths have been computed for a DNT molecule interacting with a Pt‐cluster under varying temperatures using quantum‐chemical density functional theory. Two possible initiation steps where DNT split either into nitro‐tolyl and NO2, or in nitro‐tolyl‐oxidanyl and NO, are considered. The energy barrier for the catalytic process is found to decrease significantly for the Pt catalyzed reaction compared with the uncatalyzed reaction. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem 112: 1852–1858, 2012

Classification of Raman Spectra to Detect Hidden Explosives

Raman spectroscopy is a laser-based vibrational technique that can provide spectral signatures unique to a multitude of compounds. The technique is gaining widespread interest as a method for detecting hidden explosives due to its sensitivity and ease of use. In this letter, we present a computationally efficient classification scheme for accurate standoff identification of several common explosives using visible-range Raman spectroscopy. Using real measurements, we evaluate and modify a recent correlation-based approach to classify Raman spectra from various harmful and commonplace substances. The results show that the proposed approach can, at a distance of 30 m, or more, successfully classify measured Raman spectra from several explosive substances, including nitromethane, trinitrotoluene, dinitrotoluene, hydrogen peroxide, triacetone triperoxide, and ammonium nitrate.

Nanodiamond-gated silicon ion-sensitive field effect transistor

Diamond has excellent surface chemical properties for sensing applications but active device fabrication technology is immature compared to silicon. A method for attaching nanodiamonds to commercially available silicon ion-sensitive field effect transistors is demonstrated, leading to a nanodiamond-silicon hybrid sensor. In response to pH changes, the hybrid device showed a similar response to the Si sensor, at 55 mV/pH, near the Nernst limit. Complete immersion in liquid containing different molarities of explosive precursors such NaNO2 and NaClO3, and exposure to 2,4 dinitrotoluene vapor, an analog for the explosive trinitrotoluene, gave rise to sensitive detection, while the Si ion sensitive field effect transistor device remained insensitive.

Polydiacetylene Incorporated with Peptide Receptors for the Detection of Trinitrotoluene Explosives

Because of their unique optical and stimuli-response properties, polydiacetylene-based platforms have been explored as an alternative to complex mechanical and electrical sensing systems. We linked chromic responsive polydiacetylene (PDA) onto a peptide-based molecular recognition element for trinitrotoluene (TNT) molecules in order to provide a system capable of responding to the presence of a TNT target. We first identified the trimer peptide receptor that could induce chromic changes on a PDA backbone. We then investigated the multivalent interactions between TNT and our peptide-based receptor by nuclear magnetic resonance (NMR) spectroscopy. We further characterized various parameters that affected the conjugated PDA system and hence the chromic response, including the size of end-group motifs, the surface density of receptors, and the length of alkane side chains. Taking these necessary design parameters into account, we demonstrated a modular system capable of transducing small-molecule TNT binding into a detectable signal. Our conjugated PDA-based sensor coupled with molecular recognition elements has already proven useful recently in the development of another sensitive and selective electronic sensor, though we expect that our results will also be valuable in the design of colorimetric sensors for small-molecule detection.

Fluorescent Polymer Sensor Array for Detection and Discrimination of Explosives in Water

A fluorescent polymer sensor array (FPSA) was made from commercially available fluorescent polymers coated onto glass beads and was tested to assess the ability of the array to discriminate between different analytes in aqueous solution. The array was challenged with exposures to 17 different analytes, including the explosives trinitrotoluene (TNT), tetryl, and RDX, various explosive-related compounds (ERCs), and nonexplosive electron-withdrawing compounds (EWCs). The array exhibited a natural selectivity toward EWCs, while the non-electron-withdrawing explosive 1,3,5-trinitroperhydro-1,3,5-triazine (RDX) produced no response. Response signatures were visualized by principal component analysis (PCA), and classified by linear discriminant analysis (LDA). RDX produced the same response signature as the sampled blanks and was classified accordingly. The array exhibited excellent discrimination toward all other compounds, with the exception of the isomers of nitrotoluene and aminodinitrotoluene. Of particular note was the ability of the array to discriminate between the three isomers of dinitrobenzene. The natural selectivity of the FPSA toward EWCs, plus the ability of the FPSA to discriminate between different EWCs, could be used to design a sensor with a low false alarm rate and an excellent ability to discriminate between explosives and explosive-related compounds.

Metalloporphyrin-functionalised diamond nano-particles as sensitive layer for nitroaromatic vapours detection at room-temperature

A new sensitive coating for surface acoustic wave (SAW) transducers based on diamond nano-particles functionalised with a zinc porphyrin complex is investigated for the detection of nitroaromatic vapours. The role of diamond nano-particles is to offer a stable sp 3 carbon porous matrix onto which the metalloporphyrin receptor is immobilised. This functionalised matrix can then be deposited by a layer-by-layer deposition method homogeneously on the transducer surface while featuring a high surface area. Good repeatability was obtained from sensor to sensor. The resulting sensors show a very high sensitivity of typically 120 Hz ppb −1 with a limit of detection (LOD) at 1 ppb level towards 2,4-dinitrotoluene (DNT) vapours, a tracer for explosive trinitrotoluene (TNT). The response is enhanced by more than a factor 10 when using diamond nano-particles as opposed to a transducer with only the metalloporphyrin complex deposited on the surface. The response time t 90% is approximately 4 min and the sensor response is fully reversible. The cross-sensitivity of the sensor is low when exposed to polar compounds such as ethanol or moisture. Those results are encouraging towards the development of low cost portable explosive vapour detectors. Furthermore, the carbon terminated surface of diamond nano-particles offers wide opportunities for grafting other types or receptors for chemical or biological gravimetric detection.

Detection of explosives based on surface-enhanced Raman spectroscopy

In this study we present a device based on surface-enhanced Raman scattering (SERS) for the detection of airborne explosives. The explosives are resublimated on a cooled nanostructured gold substrate. The explosives trinitrotoluene (TNT) and triacetone triperoxide (TATP) are used. The SERS spectrum of the explosives is analyzed. Thus, TNT is deposited from an acetonitrile solution on the gold substrate. In the case of TATP, first the bulk TATP Raman spectrum was recorded and compared with the SERS spectrum, generated by deposition out of the gas phase. The frequencies of the SERS spectrum are hardly shifted compared to the spectrum of bulk TATP. The influence of the nanostructured gold substrate temperature on the signals of TATP was studied. A decrease in temperature up to 200 K increased the intensities of the TATP bands in the SERS spectrum; below 200 K, the TATP fingerprint disappeared.

Ionic liquid–graphene composite for ultratrace explosive trinitrotoluene detection

A new ionic liquid (IL)–graphene composite prepared by combining IL and a three-dimensional graphene material with large specific surface area and pronounced mesoporosity was used for ultratrace trinitrotoluene detection, showing low background current, high sensitivity of 1.65 μA cm − 2 per ppb, low detection limit of 0.5 ppb and good reproducibility, which is much superior to that demonstrated by the IL–CNT and IL–graphite composites. The preparation of IL–graphene composite expands the scope of IL-based electrochemical devices.

Deep Ultraviolet Resonance Raman Excitation Enables Explosives Detection

We measured the 229 nm absolute ultraviolet (UV) Raman cross-sections of the explosives trinitrotoluene (TNT), pentaerythritol tetranitrate (PETN), cyclotrimethylene-trinitramine (RDX), the chemically related nitroamine explosive HMX, and ammonium nitrate in solution. The 229 nm Raman cross-sections are 1000-fold greater than those excited in the near-infrared and visible spectral regions. Deep UV resonance Raman spectroscopy enables detection of explosives at parts-per-billion (ppb) concentrations and may prove useful for stand-off spectroscopic detection of explosives.

TNT detection with 14N NQR: Multipulse sequences and matched filter

Nuclear quadrupole resonance (NQR) has a distinct potential to verify the presence of nitrogen bearing substances based on the unequivocal signatures of their spectra. Therefore, this technique is especially suitable for remote detection of illicit substances and explosives. Unfortunately, the inherent signal-to-noise of the most abundant explosive trinitrotoluene (TNT) is very low. Here we present an NQR method with improved sensitivity for estimation of the probability of TNT presence in the investigated object. The method consists of a spin-lock spin-echo (SLSE) multipulse sequence for signal excitation and a time domain matched filter for signal detection. We find that the signal-to-noise increases by shortening the pulse spacings, even though this means a decrease in spectral resolution. In our case, the decrease of the pulse spacings from the typical 2 ms to 540 μ s resulted in an increase of the signal-to-noise by 14 dB . A theory describing this enhancement is presented and compared to experimental results on TNT. Issues related to temperature and polymorphism variations are also discussed.

Electron attachment to trinitrotoluene (TNT) embedded in He droplets: complete freezing of dissociation intermediates in an extended range of electron energies

Electron attachment to the explosive trinitrotoluene (TNT) embedded in Helium droplets (TNT@He) generates the non-decomposed complexes (TNT)(n)(-), but no fragment ions in the entire energy range 0-12 eV. This strongly contrasts the behavior of single TNT molecules in the gas phase at ambient temperatures, where electron capture leads to a variety of different fragmentation products via different dissociative electron attachment (DEA) reactions. Single TNT molecules decompose by attachment of an electron at virtually no extra energy reflecting the explosive nature of the compound. The complete freezing of dissociation intermediates in TNT embedded in the droplet is explained by the particular mechanisms of DEA in nitrobenzenes, which is characterized by complex rearrangement processes in the transient negative ion (TNI) prior to decomposition. These mechanisms provide the condition for effective energy withdrawal from the TNI into the dissipative environment thereby completely suppressing its decomposition.

Relaxation during spin-lock spin-echo pulse sequence in N14 nuclear quadrupole resonance

In this work, we investigate off-resonance effect on the (14)N nuclear quadrupole resonance magnetization decay during the spin-lock spin-echo pulse sequence (SLSE). The compound chosen for this study is paranitrotoluene with a single (14)N site, which represents a suitable simplified model for the explosive trinitrotoluene with six nonequivalent (14)N sites. We find that the quasi-steady state magnetization exhibits dips at particular frequency offsets and more interestingly that its decay rate T(2 eff) (-1) exhibits similar dips (slower decay) at the same frequency offsets. The coexistence of dips is very important for applications where the primary use of the SLSE sequence is to increase the signal-to-noise ratio, as longer sampling times compensate for small magnetization values. A theory explaining both observations is presented which includes homonuclear dipolar interactions and spin coupling to the lattice. We show that the homonuclear dipolar interaction contributes only 20% to the total magnetization decay rate, while spin-lattice coupling is the dominant mechanism.

Preparation of hollow carbon nanospheres via explosive detonation

Hollow carbon nanospheres were prepared via a rapid detonation technique, by using negative-oxygen balance explosive trinitrotoluene and nickel powder as starting materials and inorganic acid as solvent. The carbon/metal nanocomposite particles precursor with core–shell structure was engendered firstly during detonation, and then the metal nickel core was dissolved through inorganic acid to attain the hollow carbon nanospheres. High-Resolution Transmission Electron Microscope, X-ray diffraction and Raman spectrum were used to characterize the precursor and the as-synthesized samples respectively. The results show that the external diameter of the hollow carbon nanospheres is 25–150 nm and the thickness of the wall is about 2–10 nm. The surface of hollow carbon nanosphere displays multilayer wall in structure with 0.35 nm space between the layers. Based on the experimental results, possible formation mechanism was also proposed.