Comprehensive Infrared Study of Tetryl, Dinitrotoluene, and Trinitrotoluene Compounds

Identification of Absorption Spectrum for IED Precursors Using Laser Photoacoustic Spectroscopy

Among the many commonly encountered hazards, improvised explosive devices (IEDs) remain the primary threat to military and civilian personnel due to the ease of their production and the widespread availability of their raw materials and precursors. Identifying traces of potential precursors is the first step in developing appropriate control measures. An interesting approach is to identify the precursors that are released around the site as they are handled and transformed into the final IEDs. CO2 laser photoacoustic spectroscopy can offer the spectral characterization of a number of explosives-related compounds without sample preparation. Benzene, toluene, acetone, and ethylene glycol absorption spectra were determined in the IR region between 9.2 and 10.8 µm. Each substance emitted a unique photoacoustic response corresponding to its chemical composition that could be further used to identify the explosive material.

Dual spectroscopic detection of THz energy modes of critical chemical compounds

Precise identification and sensing of organic and inorganic molecular systems are key factors in several applications in present industrial and scientific domains. While high energy modes, due to electronic interactions, are mostly impervious to the initial thermodynamic or chemical conditions, the low energy modes are sensitive to such alterations which makes them suitable for quality control purpose with sensitive spectral identification methods. Here we report for the first time, several low frequency peaks of specific nitrogen-based compounds and their derivatives, using the dual spectroscopic approach of Terahertz Time-Domain Spectroscopy (THz-TDS) and THz Raman Spectroscopy (THz-RS). Two different isomeric molecular systems have also been investigated to assess both the selectivity and specificity of low energy modes in their identification and spectral correlation in terms of molecular interactions. This information of low frequency modes can be utilized readily by pharmaceutical and agri-food industries, chemical engineering and crystal growth communities in identification, detection, quality control and industrial waste management.

Identification and analysis of organic explosives from post-blast debris by nuclear magnetic resonance

The growing threat of terrorism has triggered an urgent need to find effective ways to improve the analysis of explosives. This will aid forensic scientists in analysing the post-blast debris, which in turn helps the law enforcement agencies to frame suitable regulations. Analysis of post-blast debris is challenging as it hosts a massive amount of complexity. There are various techniques reported till date such as mass spectrometry, gas chromatography, high-performance liquid chromatography, Fourier transform infrared spectroscopy, and Raman spectroscopy for the analysis of post-blast residues. However, none of them has been able to identify the structural composition of the explosives. The current research study focuses on identifying the structural composition of the explosives from the post-blast debris using the nuclear magnetic resonance (NMR) technology. The post-blast analytes were extracted from soil samples, cleaned by the solid phase extraction (SPE) method and were rapidly analysed by the nuclear magnetic resonance spectrometer. This paper reports the identification of nitro organic explosives such as pentaerythritol tetranitrate (PETN), trinitrotoluene (TNT) and 2,4,6-trinitrophenylmethylnitramine (tetryl) in post-blast debris by 400 MHz nuclear magnetic resonance spectrometer.

Dispersion-based intertwined SEIRA and SPR effect detection of 2,4-dinitrotoluene using a plasmonic metasurface

Surface enhanced infrared absorption (SEIRA) spectroscopy and surface plasmon resonance (SPR) make possible, thanks to plasmonics nanoantennas, the detection of low quantities of biological and chemical materials. Here, we investigate the infrared response of 2,4-dinitrotoluene deposited on various arrays of closely arranged metal-insulator-metal (MIM) resonators and experimentally show how the natural dispersion of the complex refractive index leads to an intertwined combination of SEIRA and SPR effect that can be leveraged to identify molecules. They are shown to be efficient for SEIRA spectroscopy and allows detecting of the dispersive explosive material, 2,4-dinitrotoluene. By changing the in-plane parameters, a whole spectral range of absorptions of 2,4-DNT is scanned. These results open the way to the design of sensors based on SEIRA and SPR combined effects, without including a spectrometer.