Gao Shu-Ting, Xiang Shi-Qin, Jiang Yimin, Zhao Liu-Bin
School of Chemistry and Chemical Engineering, Southwest University, Chongqing, 400715, China.
Chemphyschem. 2018 Dec 19;19(24):3401-3409. doi: 10.1002/cphc.201800812. Epub 2018 Nov 20.
The chemical enhancement due to ground-state charge transfer (GSCT) and photon-driven charge transfer (PDCT) in surface-enhanced Raman scattering (SERS) has been investigated by density functional theory. Para-substituted thiophenol derivatives adsorbed on silver and gold surfaces are selected as model systems to evaluate the chemical enhancement factor. By changing the functional groups on thiophenol, we are allowed to modulate the chemical interactions between the thiophenol and the metal cluster in both ground state and charge transfer excited state. Both off-resonance and pre-resonance SERS spectra are simulated to calculate the chemical enhancement factors. The GSCT enhancement factor, EF , shows a roughly linear relationship to (ω /ω ) , where ω denotes the HOMO-LUMO gap of free molecule, and ω denotes the energy difference between the HOMO of the molecule and the LUMO of the metal. The PDCT enhancement factor, EF , is governed by the energy difference between the incident light energy and the excitation energy to the CT excited state. EF first increases and then decreases with the increase of incident light energy.
通过密度泛函理论研究了表面增强拉曼散射（SERS）中基态电荷转移（GSCT）和光子驱动电荷转移（PDCT）引起的化学增强。选择吸附在银和金表面的对取代硫酚衍生物作为模型体系来评估化学增强因子。通过改变硫酚上的官能团，我们能够调节硫酚与金属簇在基态和电荷转移激发态下的化学相互作用。模拟了非共振和预共振SERS光谱以计算化学增强因子。GSCT增强因子EF与(ω /ω )大致呈线性关系，其中ω表示自由分子的HOMO-LUMO能隙，ω表示分子的HOMO与金属的LUMO之间的能量差。PDCT增强因子EF由入射光能量与CT激发态的激发能量之间的能量差决定。EF随入射光能量的增加先增大后减小。
