In-situ detection of single particles of explosive on clothing with confocal Raman microscopy

Confocal Raman microscopy is shown to detect picogram quantities of explosives in-situ on undyed natural and synthetic fibres, and coloured textile specimens leaving potentially evidential materials unaltered. Raman spectra were obtained from pentaerythritol tetranitrate (PETN), trinitrotoluene (TNT), and ammonium nitrate particles trapped between the fibres of the specimens. Despite the presence of spectral bands arising from the natural and synthetic polymers and dyed textiles, the explosive substances could be identified by their characteristic Raman bands. Furthermore, Raman spectra were obtained from explosives particles trapped between highly fluorescent clothing fibres. Raman spectra were collected from explosives particles with maximum dimensions in the range 5-10 microm. Spectra of the explosives on dyed and undyed clothing substrates were readily obtained in-situ within 90 s and without sample preparation.