Single molecule Raman spectroscopy at the junctions of large Ag nanocrystals
Single molecule Raman spectroscopy at the junctions of large Ag nanocrystals
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DOI：
10.1021/jp034632u
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发表时间：
2003-09-18
影响因子：
3.3
通讯作者：
Brus, L
中科院分区：
文献类型：
--
作者：
Jiang, J;Bosnick, K;Brus, L
分子表面增强拉曼散射（Sers）在30-70 nm银纳米晶体的紧凑簇中显示出比自由空间单分子发光截面大几个数量级的单分子拉曼散射截面。我们分析了这一现象的某些方面与新的数值电磁计算，我们也提出了新的光谱退偏数据单分子罗丹明6 G散射。我们强调的中心作用的银飞秒辐射寿命，和激发银电子的空间分布，在近场和远场光学性能。Ag等离子体激元激发电子态的基本性质从体积激发变为表面结激发，因为两个粒子在1 nm内彼此接近。结中的吸附分子直接与金属激发态波函数相互作用，显示出电子转移引发的光化学以及增强的拉曼散射。退极化研究表明，单轴局部电磁对称的交界处网站。同时在R6 G分子线和伴随的银电子拉曼连续的强度波动出现，反映R6 G吸附-脱附动力学。我们概述了作为拉曼共振态的混合分子-金属波函数的波长依赖性质。
Molecular surface enhanced Raman scattering (SERS) in compact clusters of 30-70 nm Ag nanocrystals has shown single molecule Raman scattering cross sections that are orders of magnitude larger than free space single molecule luminescence cross sections. We analyze certain aspects of this phenomenon with new numerical electromagnetic calculations, and we also present new spectral depolarization data for single molecule rhodamine 6G scattering. We stress the central role of the Ag femtosecond radiative lifetime, and the spatial distribution of the excited Ag electrons, in the near field and far field optical properties. The fundamental nature of the Ag plasmon excited-electronic-state changes from a volume excitation to a surface junction excitation as two particles approach each other within 1 nm. Adsorbed molecules in the junction interact directly with the metallic excited-state wave function, showing electron-transfer-initiated photochemistry as well as enhanced Raman scattering. Depolarization studies show an uniaxial local electromagnetic symmetry at the junction site. Simultaneous intensity fluctuations in both the R6G molecular lines and the accompanying Ag electronic Raman continuum appear to reflect R6G adsorption-desorption kinetics. We outline the wavelength-dependent properties of a hybrid molecular-metallic wave function as the Raman resonant state.