Electrochemical Detection of 2,4,6-Trinitrotoluene Using Interdigitated Array Electrodes

Abstract

We describe the use of interdigitated array gold electrodes (IDAs) for the electrochemical detection of 2,4,6-trinitrotoluene (TNT). Our protocol generates a reversible redox couple (hydroxylamine/nitroso) from the initial reduction of TNT, which can be amplified using redox cycling at IDA electrodes. The IDA electrodes give a limit of detection for TNT at ～6 ng/mL with a linear response (r² = 0.998) between 10 and 10,000 ng/mL for static conditions and between 5 and 200 ng/mL for flow conditions (r² = 0.999).     

基于银胶纳米颗粒的痕量三硝基甲苯的表面增强拉曼光谱的实验研究

近年来对作为典型的硝基苯环类炸药的三硝基甲苯(TNT)的痕量检测受到越来越多的关注。将银胶纳米颗粒作为表面增强拉曼散射(SERS)基底,研究了10-6 mol.L-1的TNT的表面增强拉曼光谱的优化实验条件,重点研究了氯化钠溶液(NaCl)的含量以及碱性水解对TNT的表面增强拉曼光谱的影响。实验发现SERS样品中如果没有加入NaCl溶液,将观察不到TNT的SERS谱。加入的NaCl的含量必须在某一个范围之内才能观察到TNT的SERS谱,而且在这个范围之内,随着NaCl含量的增加,TNT的1 392cm-1处的拉曼峰出现先增大后减小的现象。对NaCl在TNT的SERS中的作用给予了理论解释。研究还发现TNT分子经过碱性水解后,与银纳米颗粒之间的吸附作用增强,其SERS谱的强度明显优于未经碱性水解的SERS结果。     

HMX/TNT炸药爆速与曲率及组分关系实验研究

为了确定爆轰波法向速度Dn与当地曲率κ的定量关系,用光电联合测试法研究质量配比分别为60/40、50/50及40/60时HMX/TNT炸药的Dn-κ关系.结果表明,爆轰波延滞距离z随TNT含量的增加而增大;爆轰波延滞距离z随著炸药密度P的增大而减小;随着TNT的含量增加,Dn-κ曲线的斜率逐渐增大,且斜率增大的速率为正...     

Ultrasensitive SERS Detection of TNT by Imprinting Molecular Recognition Using a New Type of Stable Substrate

We report herein a method for the ultra‐trace detection of TNT on p‐aminothiophenol‐functionalized silver nanoparticles coated on silver molybdate nanowires based on surface‐enhanced Raman scattering (SERS). The method relies on π‐donor–acceptor interactions between the π‐acceptor TNT and the π‐donor p,p′‐dimercaptoazobenzene (DMAB), with the latter serving to cross‐link the silver nanoparticles deposited on the silver molybdate nanowires. This system presents optimal imprint molecule contours, with the DMAB forming imprint molecule sites that constitute SERS “hot spots”. Anchoring of the TNT analyte at these sites leads to a pronounced intensification of its Raman emission. We demonstrate that TNT concentrations as low as 10^?12 M can be accurately detected using the described SERS assay. Most impressively, acting as a new type of SERS substrate, the silver/silver molybdate nanowires complex can yield new silver nanoparticles during the detection process, which makes the Raman signals very stable. A detailed mechanism for the observed SERS intensity change is discussed. Our experiments show that TNT can be detected quickly and accurately with ultra‐high sensitivity, selectivity, reusability, and stability. The results reported herein may not only lead to many applications in SERS techniques, but might also form the basis of a new concept for a molecular imprinting strategy.     

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.     

Highly Stable Voltammetric Detection of Nitroaromatic Explosives in the Presence of Organic Surfactants at a Polyphenol‐Coated Carbon Electrode

A polyphenol‐coated screen‐printed carbon electrode is used for highly sensitive voltammetric measurements of the 2,4,6‐trinitrotoluene (TNT) explosive in the presence of surface‐active substances. The permselective/protective polyphenol coating offers excellent resistance to surfactant fouling, while allowing facile transport of the target TNT. High levels of gelatin, humic acid and sodium dodecyl sulfate (SDS) (up to 50 mg/L) have negligible effects upon the square‐wave voltammetric TNT response. The TNT peak current and potential remain nearly the same in the presence of these organic macromolecules, as compared to substantial peak suppressions and shifts at the bare electrode. Control of the electropolymerization time was used for achieving the desired exclusion of interfering surface‐active macromolecules while allowing transport of the target TNT. The response for ppm levels of TNT is highly linear and stable for prolonged operations in the presence of surface‐active substances. By meeting the high sensitivity, selectivity, stability, portability and low‐cost demands, such voltammetric sensing holds great promise for field‐based voltammetric monitoring of nitroaromatic explosive compounds.     

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

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

Plane‐wave density functional theory investigation of adsorption of 2,4,6‐trinitrotoluene on al‐hydroxylated (0001) surface of (4 × 4) α‐alumina

This article reports the results of the theoretical investigation of adsorption of 2,4,6‐trinitrotoluene (TNT) on Al‐hydroxylated (0001) surface of (4 × 4) α‐alumina (α‐Al₂O₃) using plane‐wave Density Functional Theory. Sixteen water molecules were used to hydroxylate the alumina surface. The Perdew–Burke–Ernzerhof functional and the recently developed van der Waals functional (vdW‐DF2) were used. The interaction of electron with core was accounted using the Vanderbilt ultrasoft pseudopotentials. It was found that hydroxylation has significant influence on the geometry of alumina and such changes are prominent up to few layers from the surface. Particularly, due to the Al‐hydroxylation the oxygen layers are decomposed into sublayers and such partitioning becomes progressively weaker for interior layers. Moreover, the nature of TNT adsorption interaction is changed from covalent type on the pristine alumina surface to hydrogen‐bonding interaction on the Al‐hydroxylated alumina surface. TNT in parallel orientation forms several hydrogen bonds compared to that in the perpendicular orientation with hydroxyl groups of the Al‐hydroxylated alumina surface. Therefore, the parallel orientation will be present in the adsorption of TNT on Al‐hydroxylated (0001) surface of α‐alumina. Further, the vdW‐DF2 van der Waals functional was found to be most suitable and should be used for such surface adsorption investigation. © 2014 Wiley Periodicals, Inc.     

Improving N nuclear quadrupole resonance detection of trinitrotoluene using off-resonance effects

The off-resonance dependence of the amplitudes of the six dominant ¹⁴N nuclear quadrupole resonance (NQR) lines in commercial polymorphic trinitrotoluene (TNT) sample were experimentally determined for a wide range of experimental parameters when irradiated with the spin-lock spin-echo (SLSE) pulse sequence. We find that the amplitudes off-resonance dependence follows a sinc-like function with an additional modulation due to the spacing between the RF pulses. This dependence can be very well modeled with expressions we have derived for a single site ¹⁴N NQR in paranitrotoluene (PNT). The results can be immediately used for the reduction of the number of free parameters used in the robust signal processing models for the TNT NQR detectors.     

用酶联免疫－化学发光法测定ANT的实验研究

本文报道了酶联免疫-化学发光法测定ANT的实验研究。兔抗ANT抗血清滴度1/500～1/104,ANT检测范围0～10μg/ml.