A Look at the Origin and Magnitude of the Chemical Contribution to the Enhancement Mechanism of Surface-Enhanced Raman Spectroscopy (SERS): Theory and Experiment
A Look at the Origin and Magnitude of the Chemical Contribution to the Enhancement Mechanism of Surface-Enhanced Raman Spectroscopy (SERS): Theory and Experiment
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DOI：
10.1021/jz4012383
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发表时间：
2013-08-15
影响因子：
5.7
通讯作者：
Schatz, George C.
中科院分区：
文献类型：
--
作者：
Valley, Nicholas;Greeneltch, Nathan;Schatz, George C.
通过实验测量一组取代苯硫醇的法向拉曼光谱和表面增强拉曼光谱，并根据时间相关密度泛函理论 (TDDFT) 确定的静态极化导数进行计算。研究了银和金簇硫醇络合物，以研究化学增强作用如何随取代基变化。实验相对峰强度和位置与理论对应物非常匹配。通过实验和计算确定了每种衍生物在1600 cm(-1)附近的环拉伸模式的静态化学增强，发现由于化学取代，实验增强变化了10倍，苯单元上较强的给电子基团导致更高的增强。计算出的趋势与替代实验很好地匹配，这表明 TDDFT 在静态（低频）极限内定性（即使不是定量）描述了化学效应。开发了一种二态模型，提供了对配体到金属电荷转移激发能随取代的变化的结果的定性洞察。
Normal and surface-enhanced Raman spectra for a set of substituted benzenethiols were measured experimentally and calculated from static polarizability derivatives determined with time-dependent density functional theory (TDDFT). Both silver and gold cluster-thiolate complexes were studied to investigate how the chemical enhancement varies with substituent. The experimental relative peak intensities and positions are well-matched by their theoretical counterparts. The static chemical enhancement of the ring stretching modes near 1600 cm(-1) is determined experimentally and computationally for each derivative, and it is found that the experimental enhancement varies by a factor of 10 as a result of chemical substitution, with stronger electron donating groups on the benzene unit leading to higher enhancements. The calculated trends with substitution match experiment well, suggesting that TDDFT is describing the chemical effect qualitatively, if not quantitatively, in the static (low-frequency) limit. A two-state model is developed, providing qualitative insight into the results in terms of the variation of ligand-to-metal charge-transfer excitation energy with substitution.