Colorimetric Sensing of Nitroaromatic Energetic Materials Using Surfactant-Stabilized and Dithiocarbamate-Functionalized Gold Nanoparticles

Abstract

There is an increasing need for sensitive/selective determination of explosive traces in soil and post-blast debris for environmental and criminal investigations. A colorimetric sensor was developed to detect and quantify trinitrotoluene (TNT) and tetryl by the use of surfactant-stabilized and dithiocarbamate-functionalized gold nanoparticles (AuNPs). The sensor was manufactured by modifying the nanoparticles with the cationic surfactant cetyl trimethyl ammonium bromide and incorporating diethyldithiocarbamate (DDTC) in the AuNPs synthesis. DDTC firmly bound to AuNPs may show charge-transfer interactions with the —NO₂ groups of the analytes, and a color change proportional to analyte concentration accompanied the agglomeration of nanoparticles, at which the absorbances were recorded at 534?nm and 458?nm for TNT and tetryl, respectively. Although the limit of detection was 8?mgL^?1 (3.52?×?10^?5?molL^?1) for TNT and 0.8?mgL^?1 (2.78?×?10^?6?molL^?1) for tetryl, providing moderate sensitivity, the cost was greatly reduced compared to those of other thiol-functionalized AuNPs sensors. Possible interferences of other energetic substances in synthetic mixtures, of camouflage materials used in passenger belongings (e.g., detergent, sugar, caffeine, and paracetamol) and common soil ions were also examined. The method was statistically validated against a reference gas chromatography/mass spectrometry method. This sensor may pave the way for the manufacture of novel low-cost nitroaromatic explosive sensors made of DDTC-based pesticides.     

Photocatalytic degradation of 2,4,6-trinitrotoluene

A Pt/TiO2 photocatalyst was used in the photocatalytic degradation of 2,4,6-trinitrotoluene (TNT) under the irradiation of the simulated sunlight. The results show that the destruction of TNT is faster and more complete with the photocatalyst. The photocatalytic degradation of TNT follows first order kinet-ics. The transformation of nitryl groups of TNT molecules into nitrite and nitrate ions may be acceler-ated in the presence of the Pt/TiO2 photocatalyst. Compared with that without the catalyst, the concentration of nitrate ions was improved 32.3 times within 2.5 h.     

Intermolecular Vibration Energy Transfer Process in Two CL-20-Based Cocrystals Theoretically Revealed by Two-Dimensional Infrared Spectra

Inspired by the recent cocrystallization and theory of energetic materials, we theoretically investigated the intermolecular vibrational energy transfer process and the non-covalent intermolecular interactions between explosive compounds. The intermolecular interactions between 2,4,6-trinitrotoluene (TNT) and 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) and between 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX) and CL-20 were studied using calculated two-dimensional infrared (2D IR) spectra and the independent gradient model based on the Hirshfeld partition (IGMH) method, respectively. Based on the comparison of the theoretical infrared spectra and optimized geometries with experimental results, the theoretical models can effectively reproduce the experimental geometries. By analyzing cross-peaks in the 2D IR spectra of TNT/CL-20, the intermolecular vibrational energy transfer process between TNT and CL-20 was calculated, and the conclusion was made that the vibrational energy transfer process between CL-20 and TNTII (TNTIII) is relatively slower than between CL-20 and TNTI. As the vibration energy transfer is the bridge of the intermolecular interactions, the weak intermolecular interactions were visualized using the IGMH method, and the results demonstrate that the intermolecular non-covalent interactions of TNT/CL-20 include van der Waals (vdW) interactions and hydrogen bonds, while the intermolecular non-covalent interactions of HMX/CL-20 are mainly comprised of vdW interactions. Further, we determined that the intermolecular interaction can stabilize the trigger bond in TNT/CL-20 and HMX/CL-20 based on Mayer bond order density, and stronger intermolecular interactions generally indicate lower impact sensitivity of energetic materials. We believe that the results obtained in this work are important for a better understanding of the cocrystal mechanism and its application in the field of energetic materials.     

RDX/TNT、HMX/TNT炸药Dn(κ)关系研究

研究了不同配比HMX/TNT炸药的Dn()关系,并与不同配比RDX/TNT 炸药的Dn()关系进 行了对比。结果表明,配比相同时HMX/TNT炸药Dn()关系曲线总是在RDX/TNT炸药Dn()关系曲线 上方;RDX/TNT和HMX/TNT炸药的Dn()关系曲线随着炸药中TNT含量增加而下移。引入变量Rt 分 别将两种混合炸药的Dn()关系推广为Dn(,Rt)关系,给定变量Rt 就可以通过Dn(,Rt)关系得出相应未标 定的Dn()关系,Dn(,Rt)关系不仅可以减少实验标定次数,并且能满足DSD方法计算精度要求。     

Biosensor-based on-site explosives detection using aptamers as recognition elements

Reliable observation, detection and characterisation of polluted soil are of major concern in regions with military activities in order to prepare efficient decontamination. Flexible on-site analysis may be facilitated by biosensor devices. With use of fibre-optic evanescent field techniques, it has been shown that immunoaffinity reactions can be used to determine explosives sensitively. Besides antibodies as molecular recognition elements, high-affinity nucleic acids (aptamers) can be employed. Aptamers are synthetically generated and highly efficient binding molecules that can be derived for any ligand, including small organic molecules like drugs, explosives or derivatives thereof. In this paper we describe the development of specific aptamers detecting the explosives molecule TNT. The aptamers are used as a sensitive capture molecule in a fibre-optic biosensor. In addition, through the biosensor measurements the aptamers could be characterised. The advantages of the aptamer biosensor include its robustness, its ability to discriminate between different explosives molecules while being insensitive to other chemical entities in natural soil and its potential to be incorporated into a portable device. Results can be obtained within minutes. The measurement is equally useful for soil that has been contaminated for a long time and for urgent hazardous spills.     

Synthesis of solid state fluorescent quino[2,3-b]carbazoles via copper(II) triflate-catalyzed heteroannulation: application to detection of TNT

New analogues of solid state fluorescent quino[2,3-b]carbazoles have been synthesized from heteroannulation of quinoline alkynylaldehyde and indole. Their preliminary photophysical properties are studied and application as chemosensory material for detection of trinitrotoluene is explored.     

沉淀聚合法制备TNT分子印迹聚合物微球

以TNT为模板分子,丙烯酰胺为功能单体,二甲基丙烯酸乙二醇酯为交联剂,乙腈为溶剂,用沉淀聚合法制备了TNT分子印迹微球.紫外吸收光谱证实TNT与丙烯酰胺之间存在相互作用;平衡吸附实验结果表明,制备的分子印迹聚合物微球对TNT分子有较好的特异性吸附能力,能够选择性识别TNT分子.     

Passive standoff detection of RDX residues on metal surfaces via infrared hyperspectral imaging

Hyperspectral images of galvanized steel plates, each containing a stain of cyclotrimethylenetrinitramine (RDX), were recorded using a commercial long-wave infrared imaging spectrometer. Demonstrations of passive RDX chemical detection at areal dosages between 16 and 90 μg/cm² were carried out over practical standoff ranges between 14 and 50 m. Anomaly and target detection algorithms were applied to the images to determine the effect of areal dosage and sensing distance on detection performance for target RDX. The anomaly detection algorithms included principal component analysis, maximum autocorrelation factors, and principal autocorrelation factors. Maximum difference factors and principal difference factors are novel multivariate edge detection techniques that were examined for their utility in detection of the RDX stains in the images. A target detection algorithm based on generalized least squares was applied to the images, as well, to see if the algorithm can identify the compound in the stains on the plates using laboratory reflection spectra of RDX, cyclotetramethylenetetranitramine (HMX), and 2,4,6-trinitrotoluene (TNT) as the target spectra. The algorithm could easily distinguish between the nitroaromatic (TNT) compound and the nitramine (RDX, HMX) compounds, and, though the distinction between RDX and HMX was less clear, the mean weighted residuals identified RDX as the stain on the plate. Improvements that can be made in this detection technique are discussed in detail. As expected, it was found that detection was best for short distances and higher areal dosages. However, the target was easily detected at all distances and areal dosages used in this study. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

3,4-二硝基吡唑的合成

吡唑经硝化、重排、硝化三步反应合成了潜在的TNT替代物——3,4-二硝基吡唑,其结构经1H NMR和IR确证。并对第三步硝化反应条件进行了优化,单步收率41%。