Evaluation of a dispersive Raman spectrometer with a Ge array detector and a 1064nm laser for the study of explosives

Lewis, Mary L.; Lewis, Ian R.; Griffiths, Peter R.

doi:10.1016/j.vibspec.2005.04.002

Cited by 12 publications

(4 citation statements)

References 22 publications

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“…The wavenumbers and relative intensities of peaks observed in the acquired Raman spectrum, represented in red, match well with those of the reference Raman spectrum of trinitrotoluene (TNT) from the Renishaw library (overlaid in blue). The observed peaks can be attributed to the vibrational modes of TNT [ 4 , 5 , 7 , 13 , 14 ], including characteristic symmetric NO 2 stretching vibrations at approximately 1360 cm −1 and the asymmetric NO 2 stretching vibrations at 1534 and 1618 cm −1 . The shoulder at 1380 cm −1 may be assigned to the –CH 3 symmetric bend, and its presence sets TNT apart from most of the explosives belonging to the nitro aromatic group.…”

Section: Resultsmentioning

confidence: 99%

Combined use of direct analysis in real-time/Orbitrap mass spectrometry and micro-Raman spectroscopy for the comprehensive characterization of real explosive samples

et al. 2016

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Direct Analysis in Real Time (DART™) high-resolution Orbitrap™ mass spectrometry (HRMS) in combination with Raman microscopy was used for the detailed molecular level characterization of explosives including not only the charge but also the complex matrix of binders, plasticizers, polymers, and other possible organic additives. A total of 15 defused military weapons including grenades, mines, rockets, submunitions, and mortars were examined. Swabs and wipes were used to collect trace (residual) amounts of explosives and their organic constituents from the defused military weapons and micrometer-size explosive particles were transferred using a vacuum suction-impact collection device (vacuum impactor) from wipe and swap samples to an impaction plate made of carbon. The particles deposited on the carbon plate were then characterized using micro-Raman spectroscopy followed by DART-HRMS providing fingerprint signatures of orthogonal nature. The optical microscope of the micro-Raman spectrometer was first used to localize and characterize the explosive charge on the impaction plate which was then targeted for identification by DART-HRMS analysis in both the negative and positive modes. Raman spectra of the explosives TNT, RDX and PETN were acquired from micrometer size particles and characterized by the presence of their characteristic Raman bands obtained directly at the surface of the impaction plate nondestructively without further sample preparation. Negative mode DART-HRMS confirmed the types of charges contained in the weapons (mainly TNT, RDX, HMX, and PETN; either as individual components or as mixtures). These energetic compounds were mainly detected as deprotonated species [M–H]−, or as adduct [M + 35Cl]−, [M + 37Cl]−, or [M + NO3]− anions. Chloride adducts were promoted in the heated DART reagent gas by adding chloroform vapors to the helium stream using an “in-house” delivery method. When the polarity was switched to positive mode, DART-HRMS revealed a very complex distribution of polymeric binders (mainly polyethylene glycols and polypropylene glycols), plasticizers (e.g., dioctyl sebacate, tributyl phosphate), as well as wax-like compounds whose structural features could not be precisely assigned. In positive mode, compounds were identified either as protonated molecules or ammonium adduct species. These results clearly demonstrate the complementarity of micro-Raman microscopy combined with DART-MS. The former technique provides structural information on the type of explosives present at the surface of the sample, whereas the latter provides not only a confirmation of the nature of the explosive charge but also useful additional information regarding the nature of the complex organic matrix of binders, plasticizers, polymers, oils, and potentially other organic additives and contaminants present in the sample. Combining these two techniques provides a powerful tool for the screening, comprehensive characterization, and differentiation of particulate explosive samples for forensic sciences and homeland se...

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Section: Resultsmentioning

confidence: 99%

Combined use of direct analysis in real-time/Orbitrap mass spectrometry and micro-Raman spectroscopy for the comprehensive characterization of real explosive samples

et al. 2016

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“…, the spectra acquired from 20 pg (curve a), 200 pg (curve b) and 0.8 µg (curve c) of TNT are shown. The dominant feature of TNT molecule is the symmetric NO 2 stretching vibrations, observed at 1360 cm −1 . Because this mode, in combination with the bands at 790 cm −1 and 820 cm −1 (NO 2 scissoring modes), is also present in the SERS spectrum of 20 pg of TNT, this molecule can be clearly identified.…”

Section: Resultsmentioning

confidence: 99%

Trace level detection and identification of nitro‐based explosives by surface‐enhanced Raman spectroscopy

Botti

Almaviva

Cantarini

et al. 2013

J Raman Spectroscopy

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Methods for rapid identification of explosives and their associated compounds at trace level quantities are needed for security screening applications. In this paper, we apply the surface‐enhanced Raman spectroscopy (SERS) to detect and identify traces (as low as tens of pg) of pentaerythritol tetranitrate (PETN), ethylene glycol dinitrate (EGDN), cyclotrimethylene‐trinitramine (RDX) and trinitrotoluene (TNT) using commercially available substrates (Klarite®, Renishaw diagnostics). High quality spectra were achieved within 10 s with a compact Raman spectrometer. Principal component analysis (PCA) of the data was performed to understand what factors affected the spectral variation across the samples. It was found that 76% of the spectral variation was explained by the first three PCs. Score plots for these components showed that the energetic materials can be clearly classified on the basis of SERS spectra also at trace level quantity. Our measurements further demonstrate the potential for using SERS as fast, in situ analytical tool for safety devices, with a sensitivity which competes and, in some cases, overcomes other techniques. Copyright © 2013 John Wiley & Sons, Ltd.

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“…Later work with multichannel dispersive spectrographs has shown similar benefits of using longer excitation wavelengths to help interrogate and assess Semtex [4]. The most involved studies of the tradeoffs of excitation wavelength and resolution carried out to understand issues of spectral interference in Semtex formulations were performed by the group of Lewis et al [18][19][20][21][22]. Lewis et al were the first to suggest that for certain Semtex species intermediate NIR wavelengths shorter than 1064 nm may be useful for interrogation with lowered fluorescence [18,22].…”

Section: Preliminary Considerations: Excitation Wavelength Andmentioning

confidence: 99%

“…The first notable dispersive Raman imager that had low smile and keystone distortion properties for making clean Raman line images was the Kaiser Optical Systems, Inc., (KOSI) holographically corrected transmissive spectrograph [23,24]. This system has been thoroughly evaluated at Griffiths' lab in the 1990s [18][19][20][21][22] and found to be effective at studying mixed explosives with low overall response to fluorescence from fuel oils, binders, stabilizers, and taggants added to compounds such as Semtex [22]. The work by Lewis et al utilized a variant of the KOSI spectrograph to assess the ability to suppress fluorescence from nonexplosive additives while providing high resolution Raman spectra of the energetic constituents of Semtex and other mixed compounds.…”

Section: Design Considerations For a Line-imaging Spectrometermentioning

confidence: 99%

Design Considerations for a Portable Raman Probe Spectrometer for Field Forensics

Kelly

Blake

Bernacki

et al. 2012

International Journal of Spectroscopy

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Raman spectroscopy has been shown to be a viable method for explosives detection. Currently most forensic Raman systems are either large, powerful instruments for laboratory experiments or handheld instruments for in situ point detection. We have chosen to examine the performance of certain benchtop Raman probe systems with the goal of developing an inexpensive, portable system that could be used to operate in a field forensics laboratory to examine explosives-related residues or samples. To this end, a rugged, low distortion line imaging dispersive Raman spectrograph was configured to work at 830 nm laser excitation and was used to determine whether the composition of thin films of plastic explosives or small (e.g., ≤10 μm) particles of RDX or other explosives or oxidizers can be detected, identified, and quantified in the field. With 300 mW excitation energy, concentrations of RDX and PETN can be detected and reconstructed in the case of thin Semtex smears, but further work is needed to push detection limits of areal dosages to the ~1 μg/cm2 level. We describe the performance of several probe/spectrograph combinations and show preliminary data for particle detection, calibration and detection linearity for mixed compounds, and so forth.

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Evaluation of a dispersive Raman spectrometer with a Ge array detector and a 1064nm laser for the study of explosives

Cited by 12 publications

References 22 publications

Combined use of direct analysis in real-time/Orbitrap mass spectrometry and micro-Raman spectroscopy for the comprehensive characterization of real explosive samples

Combined use of direct analysis in real-time/Orbitrap mass spectrometry and micro-Raman spectroscopy for the comprehensive characterization of real explosive samples

Trace level detection and identification of nitro‐based explosives by surface‐enhanced Raman spectroscopy

Design Considerations for a Portable Raman Probe Spectrometer for Field Forensics

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