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Fabrication, Design, and Analytical Applications of Nanostructured Plasmonic Crystals

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Fabrication, Design, and Analytical Applications of Nanostructured Plasmonic Crystals FABRICATION, DESIGN, AND ANALYTICAL APPLICATIONS OF NANOSTRUCTURED PLASMONIC CRYSTALS BY SOMI KANG DISSERTATION Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Materials Science and Engineering in the Graduate College of the University of Illinois at Urbana-Champaign, 2014 Urbana, Illinois Doctoral Committee: Professor Ralph G. Nuzzo, Chair Professor Paul V. Braun Professor John A. Rogers Professor Nancy R. Sottos ABSTRACT Surface plasmon resonances (SPRs) are coherent oscillations of electron density occurring at the interface of a metal and a dielectric, which generate an evanescent electric field that decays exponentially within ~100-200 nm from the surface of the metal. Because this enhanced electromagnetic field is highly sensitive to local optical property changes, SPRs have been exploited for real-time, fully label-free form of chemical/biological sensing and imaging or for field-enhanced applications of electronics and photovoltaics. Soft nanoimprint lithography provides inexpensive and versatile replication method to generate uniformly ordered and defined nanostructures over large areas. Plasmonic crystals consisting of squared arrays of nanoholes with high fidelity are fabricated using soft nanoimprint lithography, which exhibit the great potential for analytical applications. The work presented in this dissertation focused on the enhancement of analytical sensitivity of a new class of bimetallic plasmonic crystal and the development of plasmonic imaging technique for complex biomolecular system using nanostructured plasmonic crystal platform. Bimetallic plasmonic crystals were demonstrated as a more sensitive substrate for quantitative bulk-refractive-index (Bulk IR) sensing and surface-enhanced Raman spectroscopy (SERS) compared to mono-metallic plasmonic crystals with the same design rule. The best performances for each application of multispectral and SERS-based sensing were obtained by manipulating the composition of thin metal film, their spatial distribution, and the design rules of the plasmonic crystals. Finite-Difference Time-Domain (FDTD) simulations were used to verify the optical behavior of bimetallic plasmonic crystals and to understand the optimized device form factor. ii A label-free optical imaging technique using plasmonic crystal was developed to quantitatively investigate the morphology and dynamic vital activities of cell. Polyelectrolyte layer-by-layer assemblies with well-defined thicknesses were used to calibrate the reflection contrast response as a function of thickness of biomolecular thin film on plasmonic crystal, which was theoretically verified through FDTD calculations. As a model system, Aplysia California pedal neurons were cultured on plasmonic crystals and quantified in both dry and liquid conditions. The capability of this plasmonic imaging technique that investigates interaction between cell and substrate in real time was verified by cell detachment using trypsin treatment. iii To my family iv ACKNOWLEDGMENTS I believe that no significant achievements are accomplished entirely on one’s own. This has been the case in my own life as well. I would like to thank all the people who have helped and supported me to complete this dissertation. I would like to begin by expressing my deepest gratitude and appreciation to my thesis advisor Prof. Ralph Nuzzo for his guidance, patience, and encouragement. His technical and editorial support has taught me innumerable lessons and insights on the workings of academic research. Ralph has granted me the freedom to design my thesis project and made me seek answers to scientific problems, which stretched my ability to look at the bigger picture. I gratefully acknowledge Prof. Paul Braun, Prof. John Rogers, and Prof. Nancy Sottos for being in my thesis committee and for encouraging and guiding me during my graduate career. I am particularly grateful for the assistance given by Prof. Jonathan Sweedler whose expertise in neurobiology helped me achieve success in my cell imaging project. I would also like to thank all the members of Nuzzo group - Sergio Sanchez, Audrey Bowen, Matthew Smalls, Evan Erickson, Eric Brueckner, Enes Oruc, Lanfang Li, Jason Goldman, Peixi Yuan, Michael Cason, Yuan Yao, Chris Corcoran, Junwen He, Mikayla Anderson, Lu Xu, Chris Daily, Joselle McCraken, Marvin Malone, David Wetzel, Brittany Rauzan, Adina Badea, Brian Lampert and Jinho Chang. I have been truly blessed to have worked with such an enthusiastic, talented, and invaluable group of people. I look forward to maintaining close contact with this network of colleagues. I would also like to appreciate those who have collaborated with me during my graduate career. I am specifically thankful for the mentorship from Jimin Yao and An-Phong Le, who helped me start my own research. I am most grateful to Stanislav Rubakhin for sharing his v knowledge of neuroscience. I would also like to extend my thanks to the staff members of Center for Microanalysis of Materials (CMM), Laser and Spectroscopy Facility (LSF), and Micro/Nanofabrication Facility (Microfab), especially Julio Soares, Scott MacLaren, and Tao Shang for their technical expertise and assistance. Finally, I wish to thank my family and my friends for their love and support throughout my study. I deeply thank my parents and grandmother for encouraging me to choose what I desired and supporting me with their unconditional love. I also want to thank my lovely sister, Soji Kang, who has been my best friend for my whole life. And special thanks to my 86 friends: Iris Choi, Hajin Im, Jennifer Kim, Soyoung Kim, and Yoojin Kim. I thank all of you for your friendship and emotional support that enabled me to survive the harsh and lonely life in Champaign. vi TABLE OF CONTENTS Chapter 1: Theory and Applications of Plasmonic Crystals ............................................................1 1.1 Introduction .............................................................................................................................1 1.2 Surface Plasmon Resonance Theory ...................................................................................... 1 1.3 Soft Nanoimprint Lithography for Plasmonic Crystal Fabrication ........................................ 5 1.4 Finite-Difference Time-Domain Computational Modeling of Surface Plasmon Resonance .................................................................................................... 8 1.5 Applications of Plasmonic Crystals ..................................................................................... 11 1.5.1 Bulk Refractive Index Sensing Using Plasmonic Crystals ......................................... 12 1.5.2 Biological/Chemical Detecting Using Plasmonic Crystals ......................................... 13 1.5.3 Two-Dimensional Imaging Using Plasmonic Crystals ............................................... 15 1.5.4 Surface-Enhanced Raman Scattering Using Plasmonic Crystals ............................... 16 1.5.5 Light Trapping for Photovoltaic Devices ................................................................... 18 1.6 Overview of Dissertation ..................................................................................................... 19 1.7 References ............................................................................................................................ 23 1.8 Figures.................................................................................................................................. 30 Chapter 2: Refractive Index Sensing and Surface-Enhanced Raman Spectroscopy Using Silver- Gold Bimetallic Plasmonic Crystals ..............................................................................................44 2.1 Abstract .................................................................................................................................44 2.2 Introduction .......................................................................................................................... 44 2.3 Experimental Materials and Methods .................................................................................. 47 2.3.1 Materials ..................................................................................................................... 47 2.3.2 Plasmonic Crystal Fabrication via Soft Nanoimprint Lithography ............................ 47 2.3.3 Bulk Refractive Index Sensing via Transmission-mode Spectroscopy ...................... 48 2.3.4 Integrated Multispectral Response Calculation .......................................................... 49 2.3.5 Surface-Enhanced Raman Spectroscopy (SERS) Measurements ............................... 50 2.3.6 Finite-Difference Time-Domain (FDTD) Simulation of Plasmonic Nanostructures ..................................................................................................................... 50 2.4 Results and Discussion ........................................................................................................ 51 vii 2.4.1 Structure and Properties of Bimetallic Plasmonic Crystals ........................................ 51 2.4.2 FDTD Modeling.......................................................................................................... 54 2.4.3 Bulk Refractive Sensitivity of Bimetallic Plasmonic Crystals ................................... 57 2.4.4 SERS Enhancement of Bimetallic Plasmonic Crystals .............................................. 60 2.5 Conclusions .........................................................................................................................
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