Selective fluorescence response and magnetic separation probe for 2,4,6-trinitrotoluene based on iron oxide magnetic nanoparticles

Despite the rapid development of nanomaterials and nanotechnology, it is still desirable to develop novel nanoparticle-based techniques which are cost-effective, timesaving, and environment-friendly, and with ease of operation and procedural simplicity, for assay of target analytes. In the work discussed in this paper, the dye fluorescein isothiocyanate (FITC) was conjugated to 1,6-hexanediamine (HDA)-capped iron oxide magnetic nanoparticles (FITC–HDA Fe₃O₄ MNPs), and the product was characterized. HDA ligands on the surface of Fe₃O₄ MNPs can bind 2,4,6-trinitrotoluene (TNT) to form TNT anions by acid–base pairing interaction. Formation of TNT anions, and captured TNT substantially affect the emission of FITC on the surface of the Fe₃O₄ MNPs, resulting in quenching of the fluorescence at 519 nm. A novel FITC–HDA Fe₃O₄ MNPs-based probe featuring chemosensing and magnetic separation has therefore been constructed. i.e. FITC–HDA Fe₃O₄ MNPs had a highly selective fluorescence response and enabled magnetic separation of TNT from other nitroaromatic compounds by quenching of the emission of FITC and capture of TNT in aqueous solution. Very good linearity was observed for TNT concentrations in the range 0.05–1.5 μmol?L^?1, with a detection limit of 37.2 nmol?L^?1 and RSD of 4.7 % (n?=?7). Approximately 12 % of the total amount of TNT was captured. The proposed methods are well-suited to trace detection and capture of TNT in aqueous solution.

Adsorption of 2,4,6-trinitrotoluene on Al(111) ultrathin film: periodic DFT calculations

The adsorption of 2,4,6-trinitrotoluene (TNT) molecule on the Al(111) ultrathin film were investigated by the generalized gradient approximation (GGA) of density functional theory (DFT). The calculations employ a supercell (4 × 4 × 2) model and three-dimensional periodic boundary conditions. The strong attractive forces between oxygen and aluminum atoms induce the N–O bond breaking of the TNT. Subsequently, the dissociated oxygen atoms and radical fragment of TNT oxidize the Al ultrathin film. The N–O bond of the o-NO₂ group is easier to rupture than that of the p-NO₂ group after the adsorption of the TNT molecule on the Al(111). Except for the breaking of the N–O bonds of the nitro group, other bonds of TNT molecule do not dissociate. The largest adsorption energy is −747.3 kJ/mol. The most of charge transfer is 3.42 e from the Al(111) to the fragment of TNT molecule. The aluminum ultrathin film is readily oxidized by the radical fragment of TNT, which is initiated by the dissociated O atoms from the nitro group.     

3-Aminopropyltriethoxysilane-functionalized manganese doped ZnS quantum dots for room-temperature phosphorescence sensing ultratrace 2,4,6-trinitrotoluene in aqueous solution

New strategies for silica coating of inorganic nanoparticles became a research hotspot for enhancing the mechanical stability of colloidal particles and protecting colloidal particles against oxidation and agglomeration, and so on. In this paper, 3-aminopropyltriethoxysilane (APTES)-functionalized Mn doped (AF MnD) ZnS QDs was prepared to be firsyly through the use of silane coupling agents to form an active layer of silica, then sol-gel reaction of TEOS co-deposited with APTES on the surface of resultant active layer of silica. The emitted long lifetime room-temperature phosphorescence (RTP) of the resultant nanomaterials allows an appropriate delay time so that any fluorescent emission and scattering light can be easily avoided. The APTES anchored on the layer of silica can bind 2,4,6-trinitrotoluene (TNT) species to form TNT anion through acid-base pairing interaction, the TNT anion species may increase the charge-transfer pathways from the nanocrystals to nitroaromatic analytes, therefore further enhance the quenching efficiency of RTP. Moreover, APTES as capped reagents can enlarge the spectral sensitivity and enhance RTP response of nanocrystals to the electron-deficient nitroaromatic and nitrophenol species. Meanwhile, AF MnD ZnS QDs also exhibited a highly selective response toward TNT analyte through significant color change and quenching of ⁴T₁ to ⁶A₁ transition emission. This AF MnD ZnS QDs based sensor showed a very good linearity in the range of 0.05-1.8 μM with detection limit down to 50 nM (quenching percentage of phosphorescence intensity of 8%) and RSD of 3.5% (n = 5). The reported QDs-based chemosensors here open up a promising prospect for the sensitive and convenient sensing of TNT explosive.     

Organoantimony Derivatives of 2,4,6-Tribromophenol

2,4,6-Tribromophenoxytetraphenylantimony was prepared in 93% yield by the reaction of pentaphenylantimony with bis(2,4,6-tribromophenoxy)triphenylantimony Ph₃Sb(OC₆H₂Br₃-2,4,6)₂ in toluene at 90°C (1 h). Bis(2,4,6-tribromophenoxy)triphenylantimony, in turn, was prepared by oxidation of triphenyl- stibine with hydrogen peroxide in the presence of 2,4,6-tribromophenol in ether at 20°C (12 h) in 47% yield, with the second reaction product being -oxobis[(2,4,6-tribromophenoxy)triphenylantimony] in which the antimony atom, according to single crystal X-ray diffraction, has a trigonal bipyramidal surrounding with the bridging oxygen atom and 2,4,6-tribromophenoxy substituents in the axial positions.     

Voltammetric platform for detection of 2,4,6-trinitrotoluene based on a molecularly imprinted polymer

New methods for determination of explosive substances as, for example, 2,4,6-trinitrotoluene (TNT), in a rapid way and at low cost are highly required. An electrochemical platform has been here developed with good characteristics of low dimension, fast response, low cost, and high selectivity. It is based on a commercially available screen printed cell with graphite ink working and auxiliary electrodes and a silver ink quasi-reference electrode. The whole cell is covered with a thick layer of cation exchanging acrylic polymer molecularly imprinted with 2,4,6-trinitrotoluene. The polymeric layer acts at the same time as electrolytic medium and selective receptor. It has been demonstrated that, in this medium, 2,4,6-trinitrotoluene is electroactive at graphite electrode, being reduced by a non-reversible reaction. The peak current (differential pulse voltammogram) is proportional to TNT concentration with limit of detection for TNT around 5?×?10^?7?M and linearity range up to 2?×?10^?5?M. The selectivity for TNT relative to other reducible compounds as, for example, nitroaromatic derivatives, and to other possible interfering substances, as negatively charged ions, is good. Measurements can be performed in not de-aerated solution and in small volumes (20 μl), so that the proposed platform is very promising for in situ determinations.

The Electrochemical Oxidation of 5‐Thio‐2‐nitrobenzoic acid (TNBA) at a Boron Doped Diamond Electrode: Demonstration of a CEC Reaction

The oxidation of 5‐thio‐2‐nitrobenzoic acid (TNBA) over a wide pH range has been investigated using cyclic voltammetry at a boron doped diamond electrode. The reaction has been shown to proceed via a CEC reaction process in which at lower pH the thiol moiety of the TNBA species has to undergo deprotonation before oxidation. DIGISIM modelling of the voltammetric profiles deduced a value of 5.2 for the pK_a of the thiol moiety which is in good agreement with that obtained from spectrophotometric data. Also reported are the rate constants for all the heterogeneous and homogeneous processes.     

Assessment of Thermal Stability and Detonation Performance of 4-Amino-1,2,4-triazolium Nitrate as compared to 2,4,6-Trinitrotoluene for Melt-cast Explosives

4-Amino-1,2,4-triazolium nitrate (4-ATN) is an energetic and non-sensitive ionic liquid, which was introduced as a good candidate in previous works for the replacement of 2,4,6-trinitrotoluene (TNT) in melt-cast explosives. Since previous studies used pure nitric acid for nitration of 4-ATN, the effect of the use of low price industrial nitric acids (50 %, 70 % and 98 %) is investigated on the percent yields of 4-ATN. The thermogravimetric and differential scanning calorimetry (TGA/DSC) are done on the synthesized 4-ATN with impure nitric acid at a heating rate of 10 K · min^–1 by the vacuum system. The obtained TGA/DSC curves confirm decomposition of 4-ATN involving melting and dissociation. Derivative thermogravimetric (DTG) curves of 4-ATN at various heating rates are applied to obtain activation energy of thermolysis by several model-free techniques. The calculated activation energies are in the range 78.7–87.7 kJ · mol^–1, which are about 10 kJ · mol^–1 more than the reported activation energy of industrial TNT (purity 98.2 %), i.e. 66–70 kJ · mol^–1. Assessments of detonation performance of 4-ATN are also compared with TNT, which show higher detonation performance of 4-ATN. Thus, 4-ATN can be used with nitramine compounds as melt-cast explosives with higher thermal stability and detonation performance than corresponding nitramine compound/TNT explosives.     

Electron impact,chemical ionization and negative chemical ionization mass spectra,and mass-analysed ion kinetic energy spectrometry–collision-induced dissociation fragmentation pathways of some deuterated 2,4,6-trinitrotoluene (TNT) derivatives

Mass-analysed ion kinetic energy spectrometry (MIKES) with collision-induced dissociation (CID) has been used to study the fragmentation processes of a series of deuterated 2,4,6-trinitrotoluene (TNT) and deuterated 2,4,6-trinitrobenzylchloride (TNTCI) derivatives. Typical fragment ions observed in both groups were due to loss of OR′ (R′ = H or D) and NO. In TNT, additional fragment ibns are due to the loss of R₂′O and 3NO₂, whilst in TNTCI fragment ions are formed by the loss of OCI and R₂′OCI. The TNTCI derivatives did not produce molecular ions. In chemical ionization (Cl) of both groups. MH⁺ ions were observed, with [M – OR′]⁺ fragments in TNT and [M – OCI]⁺ fragments in TNTCI. In negative chemical ionization (NCI) TNT derivatives produced M^?′, [M–R′]^?, [M–OR′]^? and [M–NO]^? ions, while TNTCI derivatives produced [M–R]^?, [M–Cl]^? and [M – NO₂]^? fragment ions without a molecular ion.     

Analysis of 2,4,6-trinitrotoluene, pentaerythritol tetranitrate and cyclo-1,3,5-trimethylene-2,4,6-trinitramine using negative corona discharge ion mobility spectrometry

In this study, the capability of negative corona discharge ion mobility spectrometry (IMS) for quantitative magnitude of several explosives including 2,4,6-trinitrotoluene (TNT), pentaerythritol tetranitrate (PETN) and cyclo-1,3,5-trimethylene-2,4,6-trinitramine (RDX) has been evaluated for the first time. The total current obtained with the negative corona discharge was about 100 times larger than that of IMS based on ⁶³Ni, which results in a lower detection limit and a wider linear dynamic range. The detection limits for PETN, TNT and RDX were 8×10⁻¹¹, 7×10⁻¹¹ and 3×10⁻¹⁰ g, respectively. The calibration plots for these explosives showed linear dynamic ranges of about four orders of magnitude.     

Spectroscopic and Thermal Studies on 2,4,6-trinitro Toluene (TNT)

The kinetics and mechanism of the initial stage of thermal decomposition of 2,4,6-trinitro toluene (TNT), a widely used high explosive, have been studied, together with its morphology and evolved gaseous products using thermogravimetry (TG), differential thermal analysis (DTA), infrared spectroscopy (IR) and hot-stage microscopy. The kinetics of the thermolysis has been followed by IR after suppressing volatilisation by matrixing and by isothermal TG without suppressing volatilisation to simulate actual user conditions. The best linearity was obtained for Avrami-Erofeev equation for n=1 in isothermal IR and also in isothermal TG. The activation energy was found to be 135 kJ mol⁻¹, with logA (in s⁻¹) 12.5 by IR. The effect of additives on the initial thermolysis of TNT has also been studied. Evolved gas analysis by IR showed that CO₂, NO₂, NO and H₂O are more dominant than N₂O, HCN and CO. The decomposition involves the initial rupture of the C-NO₂ bond, weakened by hydrogen bonding with the labile hydrogen atom of the adjacent CH₃ group, followed by the abstraction of the hydrogen atom of the methyl group by NO₂, generated in the initial step. This revised version was published online in August 2006 with corrections to the Cover Date.     

Synthesis of 5,6-Dihydrophenanthridine (DHPA) Sulfonamides and Subsequent Acid-Catalyzed Rearrangement to Diaryl Sulfones

Selective method of reduction of the ortho-nitro groups in 2,4,6-trinitrotoluene by hydrazine hydrate in the presence of FeCl₃ and charcoal has been elaborated. This method allows obtaining either 2-amino-4,6-dinitrotoluene or 2,6-diamino-4-nitrotoluene as well as 2,4,6-triaminotoluene from TNT.     

A clear,amine-containing poly(vinyl chloride) membrane for in situ optical detection of 2,4,6-trinitrotoluene

A membrane has been developed for the direct determination of 2,4,6-trinitrotoluene (TNT) in natural waters at levels as low as 10 ng ml^?1. A typical membrane is prepared by dissolving the following in tetrahydrofuran: 0.5 g of poly(vinyl chloride) (PVC), 0.2 ml of dioctyl phthalate to serve as a plasticizer and 0.12 ml of Jeffamine T403, a polyoxyethyleneamine which reacts with TNT to produce a colored product. The membrane is formed by casting the solution into a glass Petri dish with a diameter of 8 cm and allowing the solvent to evaporate slowly. Trace amounts of 1,3,5-trinitrobenzene (TNB), 2,4,5-trinitrotoluene (2,4,5-TNT) and N-picryl-N-methylnitramine (tetryl) also react with the membrane to produce a reddish brown color, but their visible absorption spectra differ from that of TNT. The membranes remain clear indefinitely in water. After storage for 80 days in air in a sealed container, over 80% of the amine remains in the membranes. After exposure to water for 10 days, over 40% of the amine remains in the membranes, which continue to respond to TNT. The membrane can be used to determine TNT in untreated water samples of pH 6–9. Recoveries of 0.1–4.0 mg l^?1 of TNT from spiked groundwater ranged from 95 to 105%. Results by direct analysis of turbid water samples agreed with those obtained by high-performance liquid chromatography.     

Polarographic reduction of 2,4,6-trinitrobenzene-1-sulphonic acid and some 2,4,6-trinitrophenyl-amino acid derivatives

The rapid d.c. polarography of 2,4,6-trinitrobenzene-1-sulphonic acid and its derivatives with serine (I), threonine (II), glycine (III) and histidine (IV) revealed a 3-wave reduction and a marked pH dependence of the reduction potential. The polarographic waves of the derivatives (2.5 × 10^?4 M) showed appreciable changes when sulphite ions were present, with the development of a new wave at more negative potential in ?0.01 M sulphite solutions at pH 7.0. The E_1/2 values of these waves in pH 7.0 supporting electrolyte were: (I) ?1000; (II) ?1007; (III) ?1021; (IV) ?949 mV (vs. Ag/AgCl, sat. KCl). These waves were used to determine the amino acids investigated (1–4 × 10^?4 M) in the presence of excess of 2,4,6-trinitrobenzene-1-sulphonic acid, with good precision (2%).     

Characterization of a monoclonal TNT-antibody by measurement of the cross-reactivities of nitroaromatic compounds

The characterization of a commercially available monoclonal antibody directed against the explosive 2,4,6-trinitrotoluene (TNT) is reported. The cross-reactivities of various nitroaromatic compounds have been determined by competitive enzyme-linked immunosorbent assay (ELISA). Byproducts and metabolites of TNT were examined as well as the azo dye Disperse Blue 79 and its major metabolites (2-bromo-4,6-dinitroaniline and 2-chloro-4,6-dinitroaniline, respectively). By investigation of the cross-reactivities of different spacer derivatives of TNT it could be demonstrated that the bridge-recognition of the antibody is not very pronounced. N-(2,4,6-Trinitrophenyl)-methylamine shows the highest cross-reactivity (240%) of the examined compounds. Additionally, affinity constants of several nitroaromatic compounds have been determined. The affinity constant of TNT has been calculated to 1.3 × 10⁹ L/mol from the minimal midpoint (IC50 value) of the standard curve. The detection limit achieved for TNT was 0.06 μg/L; the midpoint of the optimized assay was 0.34 μg/L. Received: 17 July 1998 / Revised: 28 December 1998 / Accepted: 1 January 1999     

Supramolecular interactions in some organic hydrated 2,4,6-triaminopyrimidinium carboxylate and sulfate salts

Four salts, namely, 2,4,6-triaminopyrimidinium 6-chloronicotinate dihydrate, C₄H₈N₅⁺·C₆H₃ClNO₂⁻·2H₂O, (I), 2,4,6-triaminopyrimidinediium pyridine-2,6-dicarboxylate dihydrate, C₄H₉N₅²⁺·C₇H₃NO₄²⁻·2H₂O, (II), 2,4,6-triaminopyrimidinediium sulfate monohydrate, C₄H₉N₅²⁺·SO₄²⁻·H₂O, (III), and 2,4,6-triaminopyrimidinium 3,5-dinitrobenzoate dihydrate, C₄H₈N₅⁺·C₇H₃N₂O₆⁻·2H₂O, (IV), were synthesized and characterized by X-ray diffraction techniques. Proton transfer from the corresponding acid to the pyrimidine base has occurred in all four crystal structures. Of the four salts, two [(I) and (IV)] exist as monoprotonated bases and two [(II) and (III)] exist as diprotonated bases. In all four crystal structures, the acid interacts with the pyrimidine base through N—H…O hydrogen bonds, generating an R₂²(8) ring motif. The sulfate group mimics the role of the carboxylate anions. The water molecules present in compounds (I)–(IV) form water-mediated large ring motifs. The formation of water-mediated interactions in these crystal structures can be used as a model in the study of the hydration of nucleobases. Water molecules play an important role in building supramolecular structures. In addition to these strong hydrogen-bonding interactions, some of the crystal structures are further enriched by aromatic π–π stacking interactions [(I) and (II)].     

The influence of steric hindrance on conformation properties and molecular structure of 2,4,6-trinitrobenzenesulfonic acid: gas electron diffraction and quantum chemical calculations

A combined gas-phase electron diffraction and quantum chemical (B3LYP/cc-pVTZ, MP2/cc-pVDZ) study of molecular structure of 2,4,6-trinitrobenzenesulfonic acid (2,4,6-tri-NBSA) was carried out. Quantum chemical calculations showed that 2,4,6-tri-NBSA possesses six conformers, which form three pairs of enantiomers with the relative energy of 0, 4.4/3.9, and 2.5/2.5 kcal/mol. It was experimentally established that at T = 444(5) K a saturated vapor over 2,4,6-tri-NBSA is, predominantly (up to 93 mol.%), represented by a low-energy enantiomers II and II′ characterized by intramolecular hydrogen bond between an H atom of the hydroxyl group and one of the O atoms of the NO₂ group. Experimental internuclear distances for the low-energy enantiomers are (?): r _h1(C–C)_av. = 1.387(4), r _h1(C–S) = 1.811(6), r _h1(S=O)_av. = 1.424(4), r _h1(S–O) = 1.579(4), r _h1(N–O)_av. = 1.214(3), r _h1(C–N)_av. = 1.491(5). Geometry of the conformer II points on existance of strong steric interactions between SO₂OH group and two ortho-nitro groups. Analysis of the orbital interactions between the substituents and benzene ring was carried out. Geometric parameters and energies of transition states between conformers were calculated (B3LYP).     

Gas phase detection of explosives such as 2,4,6-trinitrotoluene by molecularly imprinted polymers

Fast, reliable and inexpensive analytical techniques for trace detection of explosive components are in high demand. Our approach is to develop specific sensor coating materials based on molecularly imprinted polymers (MIPs). Despite the known inhibition of radical polymerisations by nitro groups and the known shrinkage of the polymer lattice during/after drying we were able to synthesize particulate MIPs by suspension polymerisation as well as thin MIP coatings by direct surface polymerisation on quartz crystal microbalances (QCM). The best method to purify the porous beads was Soxhlet extraction followed by supercritical carbon dioxide extraction (SFE with sc-CO₂) at mild conditions (150 bar, 50 °C). At least a removal of >99.7% of the template was achieved. Performance tests of TNT imprinted polymer beads showed that acrylamide (AA) and more pronounced also methacrylic acid (MAA) possessed an enhanced adsorption tendency for gaseous TNT. An adsorption of 2,4-DNT, dinitrotoluene, by these MIPs was not detected. Using 2,4-DNT as template and methacrylamide, MAAM, a positive imprint effect for gaseous 2,4-DNT was achieved with no measurable cross-sensitivity for 2,4,6-TNT.The thin MIP coatings directly synthesized on the QCMs showed thicknesses of 20 to up to 500 nm. Preliminary screening experiments were performed for five different monomers and three different solvents (acetonitrile, chloroform and dimethylformamide). Best adsorption properties for TNT vapour until now showed a PAA-MIP synthesized with chloroform. Direct measurements of the mass attachment, respectively frequency decrease of the coated QCMs during vapour treatment showed a TNT-uptake of about 150 pg per μg MIP per hour. Results look worthy for further studies.     

核黄素荧光猝灭法测定2,4,6-三硝基苯酚

基于核黄素与2,4,6-三硝基苯酚混合后产生荧光猝灭现象,建立了核黄素作为荧光探针测定2,4,6-三硝基苯酚的新方法。 在0.2 mol/L磷酸盐(NaH₂PO₄-Na₂HPO₄)缓冲溶液(pH=6.2)中,响应时间为1 min时,检测2,4,6-三硝基苯酚的线性范围为2.5~1000 μmol/L,相关系数为0.9938,检测限为0.55 μmol/L。 当加入5.00和20.00 μmol/L 2,4,6-三硝基苯酚到水样后,回收率在98.2%~103.5%之间。 方法简便,选择性好,线性范围宽,可用于实际水样中2,4,6-三硝基苯酚的定性定量分析。     

Liquid chromatographic separation of 2,4,6-trinitrotoluene and its principal reduction products

A liquid chromatographic method is described for the baseline separation of 2,4,6-trinitrotoluene (TNT) and its main reduction products. Two analytical columns (LC-18 and LC-CN) are connected in series and eluted isocratically at 1.5 ml min^?1 with water-methanol-tetrahydrofuran (60.5 + 25 + 14.5). The capacity factors (k′) are 1.4, 1.6, 5.1, 6.4 and 7.0 for 2,6-diamino-4-nitroluene, 2,4-diamino-6-nitrotoluene, TNT, 4-amino-2,6-dinitrotoluene and 2-amino-4,6-dinitrotoluene, respectively.     

Quantum chemical study on the mechanisms of nucleophilic substitution of a nitro group in 2,4,6-trinitrotoluene and 1,3,5-trinitrobenzene

The semiempirical MNDO-PM3 method is employed for calculations of the enthalpies of formation of Meisenheimerortho- andipso--complexes of 1,3,5-trinitrobenzene (TNB) and 2,4,6-trinitrotoluene (TNT) with the methoxide ion in the gas phase and in water (using the pseudocontinual point-dipole solvation model). The calculated reaction enthalpies for the replacement of a TNB and TNT nitro group with a methoxy group reveal in principle the possibility for TNB to react with the methoxide ion in water by theS _NAr mechanism through an intermediateipso--complex. In the gas phase this reaction can not follow theS _NAr mechanism due to its strong endothermicity (20 kcal/mol). The analogous nucleophilic substitution of a TNT nitro group by a methoxy group may be suppressed by the faster formation of the stable trinitrobenzene anion.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 1892–1897, November, 1993.