Developing a Method for Enhanced Explosive Detection by Surface Enhanced Raman Scattering (SERS) and Metal Enhanced Fluorescence (MEF)

Abstract

The first manuscript, "Fabrication of SERS Substrates for Explosive Detection," focuses on the development of a Surface Enhanced Raman Scattering (SERS) substrate for use in the area of explosive detection. The substrate was created by immersion plating of silver onto porous silicon, resulting in a Ag roughened surface with an average roughness of 135 nm as determined by AFM. When explosive solutions, such as trinitrotoluene (TNT) and dinitrotoluene (DNT) in ethanol, were applied directly to the substrate, detection of unique Raman bands was possible down to the 10-9-10-10 mol/cm 2 range. These results prove the technique is selective and shows promise for future work when vapor phase explosives will be investigated. The second manuscript entitled "Light Trapping to Amplify Metal Enhanced Fluorescence with Application for Sensing TNT" focuses on the use of the previously mentioned substrate for Metal Enhanced Fluorescence (MEF). By using a polymer layer as a dielectric spacer in between the Ag layer and the fluorophore, enhancement of fluorescent emission was possible even though the spacer thicknesses was 10-20 times larger than typically reported. In experiments with rhodamine 6G, the fully assembled substrate resulted in a 1600-fold enhancement of emission. Compared to the usually reported 10 1-10 2 times enhancement, the large enhancement is suspected to occur due to numerous effects. As enhancements were observed with and without the roughened Ag layer, light trapping is suggested as a contributing factor in addition to MEF. While less effective in enhancing the emission of the conjugated polymer methoxy-ethylhexloxypolyphenylene-vinylene (MEH-PPV) that is known to interact with TNT vapor, the quench in fluorescent emission of MEH-PPV occurred more rapidly when the light trapping polymer was incorporated. Rapid detection and increased sensitivity are important features to the detection of trace explosives. iv ACKNOWLEDGMENTS I would first like to acknowledge everyone in the Euler research group, specifically my research advisor, Dr. William Euler. When Dr. Euler suggested I fulfill my undergraduate research requirements in his group, I had no idea my interest in the area would lead to graduate school. Thank you for providing me with the opportunity and guidance. Also, thank you to Dr. Christopher Latendresse for dealing with me on a daily basis, ensuring a good experience in this stressful setting, and providing a wealth of knowledge. To Emily Hall, Richard Sweetman, Courtney McGowan, Hui Qi Zhang, and Shayna Albanese: I appreciate all the hard work! Your assistance in this project was vital. I am also grateful for the guidance and education provided to me by the past members of the Euler research group, specifically Dr. Drew Broduer. I could not have done this without each and every one of you. Finally, I would like to thank my family for all of their love and support. Without the encouragement of my parents, Mark and Jayne Matoian, my sister, Hillary Lesperance, and brother-in-law, Dana Lesperance, this go...