Investigation of the Importance of the Electronic Enhancement Mechanism for Surface-Enhanced Raman Scattering (SERS)
Investigation of the Importance of the Electronic Enhancement Mechanism for Surface-Enhanced Raman Scattering (SERS)
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DOI：
10.1021/acs.jpcc.0c10128
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发表时间：
2021-02-24
影响因子：
3.7
通讯作者：
Materny, Arnulf
中科院分区：
文献类型：
--
作者：
Mohaghegh, Faezeh;Tehrani, Alireza Mazaheri;Materny, Arnulf
不同的机制有助于在表面增强拉曼光谱（Sers）中观察到的非弹性散射信号的增加。所谓的电子（化学）增强机制已经研究了使用Kretschmann配置通过切换电子贡献的开和关。为此，借助于分子和金属之间的不同中间层（由自组装单层或金属氧化物层组成）防止分析物分子与金属表面的直接偶联。已经观察到，对于与金属的分离，尽管由夹层引入的与金属表面的距离仅非常小（几纳米），但是与分子可以化学吸附在金属表面上的情况相比，对于共振和预共振条件确定的增强之间的比率急剧降低。还观察到，虽然在直接接触金属表面的情况下，共振/预共振增强比是强烈的模式依赖性，这种依赖性不会发生时，分析物分子保持远离直接访问的表面。这证实了当分子从金属表面分离时过渡到纯电磁增强，并允许表征两种机制。
Different mechanisms contribute to the increase of the inelastically scattered signal observed in surface-enhanced Raman spectroscopy (SERS). The so-called electronic (chemical) enhancement mechanism has been studied using a Kretschmann configuration by switching the electronic contribution on and off. For this, the direct coupling of the analyte molecules to the metal surface was prevented with the help of different intermediate layers between molecules and metal consisting of self-assembled monolayers or a metallic oxide layer. It has been observed that for a separation from the metal, despite the only very small (a few nanometers) distance from the metal surface introduced by the interlayers, the ratio between the enhancements determined for in-resonance and preresonance conditions is drastically reduced compared to the situation where the molecules can chemisorb on the metal surface. It was also observed that while in the case of direct contact to the metal surface, the resonance/preresonance enhancement ratio was strongly mode-dependent, such dependence did not occur when the analyte molecule was kept away from direct access to the surface. This confirms the transition to a pure electromagnetic enhancement when the molecules are separated from the metal surface and allows for the characterization of the two mechanisms.