Gap Dependence of Localized Surface Plasmon Coupling in Gold Nanoring Dimer for Sensing Application

• Main Authors: Lin, Jyun-Wei, 林雋崴
• Other Authors: Lee, Po-Tsung
• Format: Others
• Language: en_US
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/85770404077177997272

碩士 === 國立交通大學 === 光電工程學系 === 99 === Localized surface plasmon mode could be induced by electromagnetic wave in metal nanostructures. When these nanostructures come in close, LSPR modes are strong coupling, leading to the electric field concentrated and enhanced in the gap of the nanostructures. In this thesis, we demonstrate a gold nanoring dimer structure design and well investigated the corresponding optical properties with varying gap sizes. Compare to typical nanoparticle dimer, nanoring dimer with more and stronger electric field distributions of LSPR bonding mode leads to better sensing applications. At first, the extinction spectra and related LSPR mode profiles of nanodisk and nanoring dimers with varying gap size are simulated and characterized by finite element method. And real devices with different gap sizes are fabricated by series of nano-fabrication process. We observed a red shift of LSPR modes and the enhanced electric field in the gap with decreasing gap size in longitudinal polarization for both nanodisk and nanoring dimers due to LSPR mode coupling. Moreover, the electric field intensity is stronger in nanoring dimer of which the sensitivity reaches to 1076 nm/RIU with gap size of 10 nm in simulation, while the sensitivity is only 901 nm/RIU for nanodisk dimer. In our experiment, high sensitivity of 663 nm/RIU for nanodisk dimer with gap size of 47 nm is obtained, which is better than the sensitivity of 531 nm/RIU for nanodisk dimer with gap size of 28 nm. We promise that it has more potential in nanosening such as protein, DNA, or toxic chemical molecule detections.