Fabrication of plasmonic probes and composites for surface enhanced Raman scattering (SERS) investigation of commercial inks and food contaminants

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Alyami, Abeer
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University College Cork
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This thesis investigates the use of different Surface Enhanced Raman Scattering (SERS)substrates for commercial inks analysis and food contaminants detection. Metal nanostructures with different plasmon frequencies have been used as SERS nanoinks for identification of dye content in blue ball-point pens. Excitation wavelengths 514 nm and 785 nm were applied with Ag nanosphere inks and Au nanorods, respectively, providing complementary information and showing significantly enhanced SERS signals compared to Raman analysis. Dense plasmonic Ag nanopastes are another kind of SERS probe that was fabricated in this thesis and used in the SERS investigation of different color ball-point pen inks. Colored ballpoint pens were analyzed using Raman bench instrumentation with 514 nm laser illumination and handheld Raman instrumentation with 785 nm laser illumination in order to elucidate the dye content in the pen ink mixtures. Other complementary analytical techniques such as UV-Vis spectroscopy and thin layer chromatography (TLC) were used for the dyes identification and to confirm results of SERS investigation. Finally, immobilized Ag particles on rigid and flexible substrates (glass and PDMS) were used as minimally invasive SERS composites, and model molecule 4-aminobenzenethiol (4-ABT) was used to test their SERS enhancement. The Ag NPs/PDMS flexible composites were applied to the in-situ SERS analysis of food contaminants and as micro-extraction films to extract pollutants from fish and fruit surfaces for ex-situ analysis. The SERS results reveal great potential for easy sampling of objects with irregular surfaces or samples with matrix that shows strong background signal. While the non-invasiveness of such probes for heritage conservation applications was not extensively tested, preliminary promising non-destructive results on mock up paper drawings were achieved, showing great potential for in situ SERS analysis of arbitrary analytical surfaces.
Raman , SERS
Alyami, A. 2019. Fabrication of plasmonic probes and composites for surface enhanced Raman scattering (SERS) investigation of commercial inks and food contaminants. PhD Thesis, University College Cork.