局域表面等离激元纳米光学传感器的原理与进展

Principles and Processes of Nanometric Localized-Surface-Plasmonic Optical Sensors

局域表面等离激元(LSP)纳米结构可将自由空间传播的光场高效地收集并会聚在其近场区域的纳米“热点”内,实现分子的高效激发,反之也可将热点内分子的光谱信息“广播”到远场。这一过程伴随着光吸收、辐射、散射及光力、共振偏移、光热等效应的极大增强,这些丰富的现象一方面为LSP纳米结构在传感领域带来了一系列应用,包括表面增强红外吸收光谱、表面拉曼光谱、表面荧光光谱、LSP折射率传感器、纳米光镊与LSP基质辅助激光解吸/电离等;但同时其行为的复杂性也给研究者理解该领域的机理与应用带来困难。针对这一状况,本文从理论与应用两方面对各类LSP传感器进行回顾和梳理,一方面利用基于准静态近似下的本征模式理论为各类LSP相关的现象提供一个统一的解析理论框架,同时对各类相关的应用,包括拉曼散射、红外吸收、荧光、折射率传感与激光解吸/离子化等领域的进展与挑战进行简要的回顾,为该领域的研究者提供一个清晰简洁的入门综述。

Localized-surface-plasmonic(LSP)nanostructures can efficiently collect light propagating in free space and converge it onto nanoscale "hot spots "in the near-field region,enabling efficient excitation of molecules.Conversely,spectral information about molecules in the hot spots can be "broadcast" to the far field.This process is accompanied by the enhancement of light absorption,radiation,scattering,light force,resonance migration,and photothermal effects.The rich phenomena associated with LSP nanostructures have resulted in a series of applications in the field of sensing,including surface-enhanced infrared-absorption spectroscopy,surface Raman spectroscopy,surface fluorescence spectroscopy,LSP refractive-index sensors,nano-optical tweezers,and LSP matrix-assisted laser desorption/ionization.However,the complexity of LSP behavior also makes it difficult for researchers to understand the mechanisms and applications of this field.For this reason,we review and sort out all types of LSP sensors from the perspectives of both theory and applications.For example,the eigenmode theory based on the quasi-static approximation provides a unified analytical theoretical framework for all kinds of LSPrelated phenomena.We provide a brief review of the progress and challenges of various related applications,including Raman scattering,infrared absorption,fluorescence,refractive-index sensing,and laser desorption/ionization,to provide a clear and concise overview for researchers in this field.