Ag nanocrystal junctions as the site for surface-enhanced Raman scattering of single Rhodamine 6G molecules
Ag nanocrystal junctions as the site for surface-enhanced Raman scattering of single Rhodamine 6G molecules
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DOI：
10.1021/jp0025476
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发表时间：
2000-12-21
影响因子：
3.3
通讯作者：
Brus, L
中科院分区：
文献类型：
--
作者：
Michaels, AM;Jiang, J;Brus, L
原子力显微镜（AFM）的测量结果表明，银纳米粒子，产生表面增强拉曼散射（Sers）的单分子的罗丹明（R6 G）都是紧凑的聚集体组成的最小的两个单独的颗粒。514.5和632.8 nm激发的比较表明，当激发波长与R6 G的吸收带共振时，单分子R6 G信号显著更高，并表明拉曼激发光谱遵循R6 G的吸收曲线。我们还观察到一个有趣的超线性功率依赖的Sers信号。平均而言，通过将入射功率增加2个数量级并将积分时间减少相同的因子以保持恒定的通量，观察到Sers强度增加了4至6倍。我们讨论了这些结果的模型，其中产生单分子Sers信号的R6G分子位于两个Ag纳米颗粒的交界处。我们还利用分子共振拉曼理论对系统进行了建模，以进一步了解增强机制。
Atomic force microscopy (AFM) measurements show that the Ag nanoparticles that yield surface-enhanced Raman scattering (SERS) of single molecules of Rhodamine (R6G) are all compact aggregates consisting of a minimum of two individual particles. Comparison of 514.5 and 632.8 nm excitation shows that the single molecule R6G signal is significantly higher when the excitation wavelength is resonant with the absorption band of R6G and suggests that the Raman excitation spectrum follows the absorption profile for R6G. We have also observed an interesting superlinear power dependence of the SERS signal. On average, by increasing the incident power by 2 orders of magnitude and decreasing the integration time by the same factor to maintain constant fluence, increases of 4 to 6 times were observed in the SERS intensity. We discuss these results in terms of model where the R6G molecule that yields single molecule SERS signals is located at the junction of two Ag nanoparticles. We have also modeled the system using molecular resonance Raman theory to provide further insight into the enhancement mechanism.