期刊
JOURNAL OF RAMAN SPECTROSCOPY
卷 45, 期 1, 页码 62-67出版社
WILEY-BLACKWELL
DOI: 10.1002/jrs.4422
关键词
electric field; charge transfer; SERS; DFT
类别
资金
- National Natural Science Foundation of China [61137005, 11374353, 10974023]
- Program for Liaoning Excellent Talents in University [LJQ2012002]
- Program for New Century Excellent Talents in University [NCET-12-0077]
The influence of a static external electric field on surface-enhanced Raman scattering is investigated by calculating the Raman spectra and excited state properties of pyridine-Au-20 complex with the density functional theory and time-dependent density functional theory method. The external electric field with orientation parallel (positive) or antiparallel (negative) to the permanent dipole moment is respectively applied on the complex. This field slightly changes the equilibrium geometry and polarizabilities, which results in shifted vibration frequencies and selectively enhanced Raman intensities. The changes of charge transfer (CT) excited states in response to the electric field are visualized by employing the charge difference densities. Further, the energy of charge transfer transition is tuned by electric field to be resonant or not with the incident light, leading to the Raman intensities are enhanced or not enhanced. At the same time, the intensities of vibration modes are sensitive to the orientation of the field. The positive electric field enhances the totally symmetric ring breathing mode (similar to 1009cm(-1)) but suppresses the trigonal ring breathing mode (similar to 1051cm(-1)). On the contrary, the mode at 1051cm(-1) is more enhanced than the mode at 1009cm(-1) when the negative electric field is applied on the complex. The Raman spectra could be modulated by tuning the strength and direction of the electric field. Copyright (c) 2013 John Wiley & Sons, Ltd.
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