Modification of Gold Nanoparticles for SERS Application in Emulsion and Lipid Systems

iv ACKNOWLEDGMENTS I would like to thank my advisor Dr. Lili He for her full support and encouragement throughout my research. The experience I gained and opportunities I had in this lab greatly exceeded my expectations, for which I am grateful. I would also like to thank Dr. Decker and Dr. Zhang for being members on my committee and for their input on my thesis. I would finally like to thank Dr. McClements for his input and assistance throughout my project. Aside from the professors, I would like to acknowledge and thank my lab mates, for their help and support over the years as well as lab members from throughout the department where their expertise was greatly appreciated. Gold nanoparticles produced using the Turkevich method were able to have their hydrophobicity modified using octanethiol in a novel method for SERS application. Both amphiliphic GNPs and hydrophobic GNPs were produced and differentiated by Raman signals. The amphiliphic GNPs were able to enhance the SERS signals of the protein emulsifier in the emulsion in situ and the hydrophobic GNPs were able to enhance the SERS signals from canola oil. Further purification of the hydrophobic GNPs proved to have higher enhancement and sensitivity, but still poor consistency which is typical of SERS. Monitoring lipid oxidation using Raman and SERS using alternative approaches was the primary objective of the thesis. The purified GNPs were capable of enhancing the canola oil over two weeks, but the poor consistency led to no major trends. Using normal Raman, a triphenylphosphine oxidation reaction was capable of producing a peroxide value correlation in a very simple and rapid manor. Using a gold nanoparticle modified stainless steel wire, the headspace volatiles from canola oil oxidation were able to be enhanced, but with poor consistency. Silver dendrites were used to enhance the canola oil signal but with poor resolution. A combination of silver dendrites and GNPs were used to slightly improve enhancement, but not as strong as GNPs alone.