Theoretical study on contribution of charge transfer effect to surface-enhanced Raman scattering spectra of pyridine adsorbed on Ag(n) (n = 2-8) clusters |
| |
Authors: | Liu Shasha Li Yuanzuo Zhao Xiuming Liu Xiaoxia Chen Maodu |
| |
Institution: | aSchool of Physics & Optoelectronic Technology, Dalian University of Technology, Dalian 116024, PR China;bDepartment of Chemistry, Northeastern University, Shenyang 110004, PR China;cBeijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100080, PR China |
| |
Abstract: | We investigate surface-enhanced Raman scattering (SERS) spectra of pyridine–Agn (n = 2–8) complexes by density functional theory (DFT) and time-dependent DFT (TDDFT) methods. In simulated normal Raman scattering (NRS) spectra, profiles of pyridine–Agn (n = 2–8) complexes are analogical with that of isolated pyridine. Nevertheless, calculated pre-SERS spectra are strongly dependent on electronic transition states of new complexes. Wavelengths at 335 nm, 394.8 nm, 316.9 nm and 342.6 nm, which are nearly resonant with pure charge transfer excitation states, are adopted as incident light when simulating pre-SERS spectra for pyridine–Agn (n = 2–8) complexes, respectively. We obtain enhancement factors from 103 to 105 in pre-SERS spectra compared with corresponding NRS spectra. The obvious increase in Raman intensities mainly result from charge transfer resonance Raman enhancement. A charge difference densities (CDDs) methodology is adopted in describing chemical enhancement mechanism. This methodology aims at visualizing charge transfer from Agn (n = 2–8) clusters to pyridine on resonant electronic transition, which is one of the most direct evidences for chemical enhancement mechanism. |
| |
Keywords: | Chemical mechanism via charge transfer Theoretical study Pre-SERS Pyridine Pyridine&ndash Agn (n = 2&ndash 8) complexes |
本文献已被 ScienceDirect PubMed 等数据库收录! |
|