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Abstract(s)
The importance of human fingermark identification and individualization for forensic purposes cannot be overemphasized. Consequently, the need for robust and effective techniques explains the continued and intensified research in this field of forensics despite the fact that there are already numerous operational techniques available to forensic identification experts. Novel approaches have recently been adopted to understand the chemistry of latent fingermarks and produce reagents targeting some of these constituents of latent fingermarks. Nanotechnology and surface-enhanced Raman spectroscopy (SERS) are gaining more attention in this area of endeavor, where nanoparticle-based reagents are increasingly being developed and optimized for application in latent fingermark enhancement and chemical imaging of such latent fingermarks. In this study, surface-enhanced Raman spectroscopy has been used to investigate the applicability of Raman reporter-labeled metallic nanoparticles to the enhancement of latent fingermarks. Rhodamine 6G and 4-mercaptobenzoic acid have been investigated as Raman reporters adsorbed on either gold or silver nanoparticles. The functionalized nanoparticles were deposited onto latent fingermark samples and characteristic Raman vibrational bands of the reporter molecules when adsorbed on nanoparticles (1076 cm-1 and 1583 cm-1 for 4-mercptobenzoic acid; 610 cm-1, 1360 cm-1 1505 cm-1 and 1648 cm-1 for rhodamine 6G) were monitored and showed very low variability of peak position between samples (coefficient of variation generally < 0.5%). Adsorption of reporter molecules on nanoparticles was characterized using UV-vis absorption spectroscopy as well as the behaviour of characteristic Raman shifts of the molecules which gave an indication of successful adsorption. Rhodamine 6G in this study however had a weak adsorption onto silver nanoparticles as a result of suboptimal amounts of the dye molecule used. Preferential deposition of the Raman reporter-labeled nanoparticles on fingermark ridges was also observed with fingermarks deposited on non-porous surface (glass slide). This study demonstrates the potential for SERS chemical imaging of latent fingermarks based on characteristic SERS vibrational bands from reporter molecules adsorbed on metallic nanoparticles and deposited onto latent fingermarks.
Description
Dissertação de Erasmus Mundus para obtenção do grau de mestre em Técnicas Laboratoriais Forenses
Keywords
Human fingermark identification Nanotechnology Raman spectroscopy Raman reporters