LIBS Detection of Explosives in Traces

Abstract

Laser-induced breakdown spectroscopy is one of the most exciting topics in the whole field of analytical science. Among the several expanding applications of LIBS, the analysis of explosives is gaining acceptance due to the unique capabilities of LIBS for inspection of distant samples, for recognition of materials behind a barrier or for identification of objects in motion, to name just a few examples. Although LIBS is a technique for elemental analysis, recent insights in the understanding of the chemistry of plasma plumes have boosted the use of LIBS for identification of organic compounds. In this chapter, the uses of LIBS for the detection, sorting and identity assignment of explosives is reviewed. The first section of this contribution is devoted to the fundamentals of explosive responses, with a discussion of the strong and weak points of LIBS for this application. The next section deals with the specific instrumentation used for laboratory and field work, from man-portable units to stand-off systems. A discussion on the several chemometric tools used for identification and sorting of explosives follows. Data fusion strategies for improving the distinction between harmless and explosive compounds are presented. Finally, a conclusions section outlines the current achievements and the future needs in this application.

Sensing Signatures Mediated by Chemical Structure of Molecular Solids in Laser-Induced Plasmas

“…14 Progress in laser ablation together with monitoring of optical emissions has emerged as a valuable method for characterization of laser-induced organic plasmas. [15][16] Most work has been focused on exploration of the spectrally resolved signatures from emission decay of gas-phase ions and fragments.…”

“…14 Progress in laser ablation together with monitoring of optical emissions has emerged as a valuable method for characterization of laser-induced organic plasmas. 15,16 Most work has been focused on exploration of the spectrally resolved signatures from emission decay of gas-phase ions and fragments. Apart from the well-known atomic and ionic emissions of carbon, hydrogen, nitrogen, and oxygen, several molecular bands mainly due to CN radicals and C 2 dimers and weaker emissions corresponding to CH, NH, and OH fragments 17 have been observed.…”

Unveiling the identity of distant targets through advanced Raman-laser-induced breakdown spectroscopy data fusion strategies

“…At these circumstances, that is, when findings are judged on the basis of particular spectral information, the decision about target's identity might be limited. For instance, LIBS has a restricted ability on identify those inspected targets that share elemental composition, as organics [20]. Similarly, although interaction between excitation light and the target might lead to a unique spectral fingerprinting of the material, selectivity of Raman suffers when the same functional group is involved in the composition of the interrogated targets [21].…”

Improving the signal-to-noise ratio of atomic transitions in LIBS using two-dimensional correlation analysis

“…Furthermore, the information in the varying intensities with different composition of elements coupled with machine learning techniques can be used for classification and identification of samples. Because of its versatile nature, being quick and minimal sample preparation requirements, LIBS found fantastic applications in diverse fields such as bacteria classification [3][4][5] , to geological materials 6 in planetary exploration, minerals, 7 archelogy, 8,9 explosive detection, 10,11 , trace element detection, 12,13 in the study of historic paintings, 14 and in the study of fundamental plasma properties. 15 This technique also found diverse applications because of its suitability to combine with Raman spectroscopy 16,17 to be able to operate easily in double-pulse and/or stand-off mode 18 .…”