奈米尺度光與物質作用之增益和控制Part 1: 自組裝金奈米粒子表面增益拉曼效應之比較研究Part 2: 電漿奈米電路中模態之轉換

表面增益拉曼光譜(SERS)是以粗糙的金屬表面或是金屬奈米粒子來增強待測物的拉曼散射，此技術具有相當高的靈敏度且已被廣泛應用，然而真正的SERS機制卻仍有待商榷。因此本論文的第一部分主要研究與比較具有不同的形貌、尺寸和晶面的自組裝金奈米粒子，在作為表面增益拉曼光譜的基材時，其拉曼訊號的相對強弱，並且提出理論假設，從金奈米粒子的近場強度、接觸面積以及不同晶面與苯硫酚分子的鍵結能來解釋實驗上所得到的拉曼散射強度增益值。實驗上發現菱形20面體的金奈米粒子具有最強的SERS訊號，而理論上推演出不同晶面之奈米金粒子的SERS增益值也與實驗數據部分吻合，此研究亦提供了日後選用SERS基材的準則。另外，為了能夠調控光場與物質之作用，本論文亦研究於電漿奈米電路中設計模態轉換器，利用控制電漿奈米雙線傳輸線上電漿子的相位，來達到被動式或主動式的調控波導模態，進而控制光場之阻抗，未來可用於調控奈米尺度下光和物質間的作用。藉由調控雙線傳輸線之長度或寬度以及環境折射率，其模態轉換器成功地於橫向電波模態(TE mode)或橫向磁波模態(TM mode)之間自由轉換。為了能夠實現模態轉換器以及觀察種種光學現象，本論文中亦建立了自組裝的共軛焦雷射掃描顯微鏡以及近場光學掃描顯微鏡。

關鍵字

電漿子；表面增益拉曼光譜；光與物質之作用；電漿奈米電路；電漿模態轉換器；金奈米粒子

並列摘要

Surface enhanced Raman spectroscopy (SERS) has ultrahigh sensitivity and is now wide used. SERS makes use of rough metal surfaces or metallic nanoparticles to enhance the Raman scattering of a specimen. However, the mechanism of the enhancement effect is still open to question. Thus, in the first part of the thesis, we try to study and compare the SERS signals from thiophenol molecules attached to self-assembled gold nanoparticles with distinct shape, size and facet. We also make an assumption to explain the experimental data from the aspect of electromagnetic theory by analyzing the near-field intensity of gold nanoparticles and chemical effect by calculating the surface area of gold nanoaprticles and binding energies of thiophenol molecules adsorbed on different crystal facets. We discovered that rhombic dodecahedron gold nanoparticles with facet have the largest Raman scattering intensity and the comparative SERS intensities predicted by theoretical calculations also consist with the experimental data. This research provides a criterion of choosing SERS-active substrates hereafter. Besides, for the sake of controlling the interaction between light with matter, we propose and design mode converters in a plasmonic nanocircuit by manipulating the phase of surface plasmon on TWTL to achieve passive or active control of the guided modes and then it is capable of controlling the impedance of the optical field. Hence, it offers the possibility to handle nanoscale light-matter interaction. The mode conversion transforms successfully at will between transverse magnetic (TM) mode and transverse electric (TE) mode by means of differing in the path length or cross section between two wires as well as the surrounding refractive index. To realize the mode converters and monitor the optical phenomena, I build up an optical system containing a home-made confocal laser scanning microscope and a near-field scanning microscope.

並列關鍵字

Plasmonic ； SERS ； light-matter interaction ； plasmonic nanocircuit ； plasmonic mode converter ； gold nanoparticle

參考文獻

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3 Pandian Senthil, K.; Isabel, P.-S.; Benito, R.-G.; Abajo, F. J. G. d. & Luis, M. L.-M. “High-yield synthesis and optical response of gold nanostars,” Nanotechnology 19, 015606, (2008).

5 Hofmann, A.; Schmiel, P.; Stein, B. & Graf, C. “Controlled formation of gold nanoparticle dimers using multivalent thiol ligands,” Langmuir 27, 15165-15175, (2011).

6 Edgar, J. A.; McDonagh, A. M. & Cortie, M. B. “Formation of gold nanorods by a stochastic “popcorn” mechanism,” ACS Nano 6, 1116-1125, (2012).

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國際替代計量

奈米尺度光與物質作用之增益和控制Part 1: 自組裝金奈米粒子表面增益拉曼效應之比較研究Part 2: 電漿奈米電路中模態之轉換

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