金奈米粒子非線性散射之研究與超解析顯微術應用

Investigation of Nonlinear Scattering in a Single Gold Nanoparticle and Its Application to Superresolution Microscopy

李炫(Hsuan Lee) ； 黃彥達(Yen-Ta Huang) ； 朱士維(Shi-Wei Chu)

《科儀新知》 199期 (2014/06) Pp. 66-73

摘要

光學顯微鏡的解析度受繞射所限，一般只能達到約波長的一半。過去二十年中，發展了許多新穎的超解析顯微技術，主要利用螢光的開關或是飽和等非線性光學特性來達到超高解析度，然而螢光具有光漂白的問題，無法做長時間的觀察。在此研究中，我們首次發現電漿奈米粒子散射具有可飽和的非線性現象。在不同的激發波長下，達到飽和散射所需的強度也不同，可推論出此飽和特性跟表面電漿共振有直接的關係。我們並利用此可飽和的散射作為顯微鏡對比機制，結合飽和激發顯微術，實現空間解析度小於80 nm的超解析顯微術。以散射為對比的顯微技術，不論觀察多久，信號都不會變弱，因此實現了一種可以長時間觀察的超解析顯微技術。此外，新發現的非線性散射現象，將在奈米電漿子以及超解析顯微術的領域開拓新的研究方向。

並列摘要

Conventionally, the resolution of optical microscopy is limited to about half of wavelength, due to diffraction barrier. During the past two decades, super-resolution imaging was realized by several innovative approaches, which were based on manipulating the on/off switching of fluorophores, or by saturation of fluorescence emission. However, fluorescence exhibits a severe issue of bleaching, significantly preventing long-term observation. To prevent the photobleaching of fluorophores, we demonstrate novel super-resolution imaging based on saturation of scattering from plasmonic particles, for the first time. From spectral studies, we have confirmed the saturation is directly linked to surface plasmon resonance effect. With the aid of saturation excitation microscopy, we have achieved optical resolution below 80-nm based on scattering, which is continuously observable without bleaching. Our study will open up a completely new paradigm for not only nano-plasmonics but also super-resolution microscopy.