Military grade explosives such as pentaerythritol tetranitrate (PETN) remain both security and environmental threats. One common method of detecting explosives involves colourimetric testing which is rapid and portable, however, this method lacks specificity as it reacts to specific functional groups in a molecule, therefore resulting in false positives for non-explosive molecules containing the same functional group. Bulk samples of explosives can also be detected using X-ray diffraction and ion-mobility spectroscopy, however, these techniques require large, expensive instrumentation and highly trained staff to operate them. The techniques commonly used today for explosive detection work best on nitro-aromatic explosives. The aim of this research was to develop a method of detecting PETN in a quick and sensitive assay format, which could be used for in field analysis. Initially, this research focused on the detection of PETN using a previously commercially available substrate called KlariteTM. The enhancement observed was investigated to find out if the PETN molecule concentrated into the structural pits of the substrate, or the roughened gold top layer was responsible for the enhancement. However, evidence was found to support both theories and no conclusions could be drawn. As it was difficult to detect low levels of PETN using surface enhanced Raman scattering (SERS), it was decided to fragment the analyte and use the product in an azo reaction. This resulted in the development of four assays which could detect PETN using absorption and/or resonance Raman spectroscopy. However, the assays required a lengthy reaction process (75 minutes), making the assays unlikely to be useful for in field detection. Finally, the resonance Raman assays were further developed into a single SERS assay, which resulted in more sensitive detection of PETN. The timings of the reaction were optimised and reduced so completion was reached within 10 minutes.The assay was found to be translatable for use in field detection as the Raman instrumentation used was portable, and the reaction was fast. Overall, SERS substrates and Raman spectroscopic techniques (resonance Raman and SERS) can be applied to detect PETN to 1 mg L-1 (3.2 μM), leading to comparable limits of detection and quicker reaction times than those found in recent literature regarding the detection of PETN with similar methods.
|Date of Award||18 Dec 2020|
- University Of Strathclyde
|Sponsors||University of Strathclyde|
|Supervisor||Duncan Graham (Supervisor) & Karen Faulds (Supervisor)|