Marr James M, Schultz Zachary D
University of Notre Dame, Department of Chemistry and Biochemistry, Notre Dame, IN 46556.
J Phys Chem Lett. 2013 Oct 3;4(19). doi: 10.1021/jz401551u.
Electric fields associated with Raman enhancements are typically inferred from changes in the observed scattering intensity. Here we use the vibrational Stark effect from a nitrile reporter to determine the electric field dependent frequency shift of cyanide (CN) on a gold (Au) surface. Electroplated Au surfaces with surface enhanced Raman (SERS) activity exhibit larger Stark shifts near the edge and in areas with large roughness. The Stark shift is observed to correlate with intensity of a co-adsorbed thiophenol molecule. Gap-mode Tip enhanced Raman scattering (TERS), using a Au nanoparticle tip, show dramatic shifts in the CN stretch that correlate to enhancement factors of 10 in the gap region. The observed peak widths indicate the largest fields are highly localized. Changes in the nitrile stretch frequency provide a direct measurement of the electric fields in SERS and TERS experiments.
与拉曼增强相关的电场通常是从观察到的散射强度变化中推断出来的。在这里，我们利用腈类报告分子的振动斯塔克效应来确定金（Au）表面上氰化物（CN）的电场依赖性频移。具有表面增强拉曼（SERS）活性的电镀金表面在边缘附近和粗糙度较大的区域表现出更大的斯塔克频移。观察到斯塔克频移与共吸附的硫酚分子的强度相关。使用金纳米颗粒尖端的间隙模式尖端增强拉曼散射（TERS）显示出CN伸缩振动的显著频移，这与间隙区域中10的增强因子相关。观察到的峰宽表明最大的电场是高度局域化的。腈伸缩振动频率的变化为SERS和TERS实验中的电场提供了直接测量。
