Photothermal Energy Conversion by Plasmonic Nanoparticles by Joseph Raymond Cole A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE Doctor of Philosophy

Photothermal Energy Conversion by Plasmonic Nanoparticles By Joseph Raymond Cole Photothermal energy conversion is important when designing optically active devices based on plasmonic nanoparticles. Many early applications of these nanoparticles, like photothermal tumor ablation, drug delivery, and microfiuidic devices, depend on the conversion of light to heat. In this dissertation, we compare three nanoparticle species' theoretical absorption efficiency from electromagnetic calculations with their photothermal transduction efficiency from measurements of temperature in an illuminated system. Several mechanisms that may account for differences between the two efficiencies are suggested. With a view specifically toward clinical applications, our analysis assumes a random orientation of nanorods, as would occur naturally in the tumor vasculature. For the samples studied here, photothermal transduction efficiencies differed only by a factor of two or three, regardless of particle type and concentration. Both experiment and theory show that particle size plays a dominant role in determining transduction efficiency, with smaller particles more efficient for heating and larger particles for combined heating and imaging. Additionally, we evaluate the potential of mixtures of plasmonic nanoparticles for CO2 scrubbing substrates that could be used in space applications. These measurements indicate possible dynamic nanoscale effects that need to be accounted for when modeling photothermal transduction. Acknowledgements Writing a Ph.D. dissertation is by far the most difficult thing I have ever attempted. If my previous life was like a baby gaining enough endurance hold its head up and see the world, for me writing this relatively short and unremarkable document was like Atlas bearing the heavens on his shoulders. So, even though I am quite cognizant of the most probable fate of this document (that it will collect dust, lost among thousands of identically covered documents until some distant calamity befalls the world), I am now quite happily munching an apple while I collect a few extra for Heracles. Unlike the Titan however, I would have been crushed by the weight many years ago without the support, friendship, and love of a very large number of people. I very much want my committee, and especially my advisor, Naomi Halas, to know how thankful I am for their firm and consistent prodding to become a better scientist. I hope all of the students and staff of the Halas research group that I worked, ate, drank, debated, and suffered with over the years already know how much their friendship means to me. Most of all, I want to record here that none of this would have been possible without the loving support of my family and my wife, Elizabeth. They are the people who saw quality in me even when I was an eighteen year old, minimum wage cashier working in a dingy pizza parlor. To all of the above, I may be eating apples today, but just know that I know that I would not be without you. I hope that the future holds more challenges greater than this one, but only if these and others I have not yet met will be around to help me.