Surface enhanced Raman spectroscopy of individual rhodamine 6G molecules on large Ag nanocrystals
Surface enhanced Raman spectroscopy of individual rhodamine 6G molecules on large Ag nanocrystals
复制标题
DOI：
10.1021/ja992128q
复制
发表时间：
1999-11-03
影响因子：
15
通讯作者：
Brus, LE
中科院分区：
文献类型：
--
作者：
Michaels, AM;Nirmal, M;Brus, LE
为了探索局部电磁场增强与能够观察单分子拉曼光谱的大 SERS（表面增强拉曼散射）增强之间的关系，我们测量了单个银颗粒的共振瑞利散射光谱和罗丹明 6G 拉曼光谱。我们的设备结合了用于共振瑞利测量的暗场光学显微镜技术和掠入射拉曼光谱技术。瑞利光谱表明柠檬酸盐还原的 AE 胶体极其不均匀。只有部分由盐诱导聚集产生的较大颗粒才会表现出较大的 SERS 效应。与 Nie 和 Emery 的工作一致，我们发现一些纳米晶体表现出巨大的单分子 R6G SERS 强度。虽然所有 SERS 活性粒子在 514.5 nm 激光波长处都有一些共振瑞利散射，但共振瑞利光谱与 SERS 强度之间没有相关性。我们讨论了一个模型，其中巨大的 SERS 强度是由单个化学吸附分子与光激发大银粒子中的弹道电子相互作用产生的。该模型是 SERS 标准局域电磁场模型和贵金属中等离激元相移的高表面灵敏度的自然结果。
To explore the relationship between local electromagnetic field enhancement and the large SERS (surface enhanced Raman scattering) enhancement that enables the observation of single molecule Raman spectra, we measure both resonant Rayleigh scattering spectra and rhodamine 6G Raman spectra from single Ag particles. Our apparatus combines the techniques of dark-field optical microscopy for resonant Rayleigh measurements, and grazing incidence Raman spectroscopy. The Rayleigh spectra show that the citrate-reduced AE colloid is extremely heterogeneous. Only the larger particles, in part created by salt induced aggregation, show a large SERS effect. In agreement with the work of Nie and Emery, we find that a few nanocrystals show huge single molecule R6G SERS intensities. While all SERS active particles have some resonant Rayleigh scattering at the 514.5 nm laser wavelength, there is no correlation between the resonant Rayleigh spectra and the SERS intensity. We discuss a model in which huge SERS intensities result from single chemisorbed molecules interacting with ballistic electrons in optically excited large Ag particles. This model is a natural consequence of the standard local electromagnetic field model for SERS and the high surface sensitivity of plasmon dephasing in the noble metals.