Plasmonic cavities via silver nanocubes self-assembled on massed silver surface for surface enhanced Raman scattering

• Main Authors: Shu-ChunCheng, 鄭淑君
• Other Authors: Ten-Chin Wen
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/46221377908312170862

博士 === 國立成功大學 === 化學工程學系 === 104 === This study investigates the electromagnetic(EM) field behaviors on the plasmonic cavities (PC) formation and the corresponding SERS responses. Various PC on a large scale from massive nanogaps are formed by self-assembling silver nanocubes or nanospheres atop the massed silver surface via 1, 2-ethanedithiol monolayer as an ultrathin spacer. The simulation results by finite-difference time-domain method demonstrate that the EM field strength and frequency of plasmon resonance are strongly affected by the shape of nanoparticles, the gap width between Ag nanocubes and the massed Ag surface, and the configuration of substrates. The stronger PCs are induced from nanocubes than nanospheres owing to the strong plasmonic interaction between the parallel silver surfaces of Ag nanocubes and the massed Ag surface. Besides, the electromagnetic field is especially concentrated at the sharp corners. A red-shift in wavelength of surface plasmon resonance increases with the decrease in gap width. Nanocube-insulator-metal geometry with 2 nm gap width (2-NcIM) possesses the strongest EM field distribution and its PC forms near 633 nm radiation, being magnificently useful for surface enhancement Raman scattering (SERS) application. The enhancement factor (EF) calculated by integrating the ratio of EM field intensity of substrate to background to the power of four, is 1.16×109. The homogeneous distribution of Ag nanocubes on 2-NcIM via self-assembled monolayer of 1, 2-ethanedithiol renders supreme performance in SERS analysis with enhancement factor 2.8×108 by detecting 10－9 M rhodamine 6G solution, confirming the validity of the simulation results. Otherwise, high reliability and high precision is shown via 6.6％ relative standard deviation from 20-sites measurements and calibration line with 99.9％correlation coefficient from 10－6 M to 10－9 M R6G solution. It also successes in quantitative analysis by detecting 10－6 M to 10－8 M adenine solution with high reliability (5.2 ％ standard deviation). These result pumps us to believe that the 2-NcIM substrate is suitable used for ultra-sensitive detection for trace biochemicals in extremely low concentration.