In recent years, Raman spectroscopy has become popular in forensic science. However, most of the work in this area has used laboratory-based, research grade instruments. The aim of this thesis was to establish new methods for forensic Raman analysis which would be suitable for use in laboratories and at crime scenes using commercial portable Raman instruments. Although these systems could potentially enable forensic field analysis, they have been designed with very limited sampling options, typically with very short focal length excitation/collection optics. This makes it difficult to actually use them as intended at crime scenes due to problems locating and focusing on the samples. Here, a new sampling arrangement which involved changing the optical assemblies for excitation/collection and incorporation of a webcam for sample viewing was designed was constructed and tested. This gave a modified system that was actually usable as a handheld device. A new method for analysis of propellant and organic gunshot residue based on a combination of macroscopic observation of particle morphology and Raman spectroscopy for composition analysis was developed. The main obstacle in this work was fluorescence. However, washing with a 95:5 methanol:ethanol mixture removed the fluorescent interference from most propellants so Raman spectroscopy could be used to identify the chemical components of propellants/organic GSR particles and distinguish them from background particles. Raman spectroscopy has also been successfully employed to identify the main pigments/dyes in pen inks and to discriminate between them. Blue gel and liquid ink pens were examined using 633 and 785 nm excitation, it was found that the discrimination given by either of these excitation wavelengths was similar to the combination of both. In addition, the best way to discriminate between the pens was to combine normal Raman measurements on the pigment based inks with SERS on the dye-based systems.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:676519 |
| Date | January 2014 |
| Creators | Ho, Yen-Cheng |
| Publisher | Queen's University Belfast |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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