Surface-enhanced Raman scattering of uracil and uracil dimer on silver by density functional method

The adsorbed structures, Surface-enhanced Raman scattering (SERS) and pre-resonance Raman spectra of the UAg and U〈 〉UAg complexes are calculated using density-functional theory (DFT) method with B3LYP/6-311g (d, p) (C, H, O)/Lanl2dz (Ag) basis set. The uracil and uracil dimer prefer to a perpendicular orientation adsorbed on the Ag surface via atom O8 site. The SERS of the UAg and U〈 〉UAg complexes are similar with the normal Raman spectra of the isolated uracil and uracil dimer but with an enhancement factor less than 10. The enhancement mechanism is ascribed to the ground state static chemical enhancement from the static polarizability changes. The pre-resonance Raman spectra of the complexes are obtained at 316 nm and 315 nm, in which the enhancement factors are up to 103–104. The greatest enhancement factor is observed for the C2O8 stretching vibration, caused by the electron transfer from the molecules to Ag atom. The charge transfer resonant enhancement plays the major role in the molecule–metal system.

Graphical abstractUnder the action of the incident light resonance excitation, the enhancement factors of the pre-resonance Raman spectra of the UAg and U〈 〉UAg complexes are up to 103∼104, which are caused by the charge transfer from uracil molecule or uracil dimer to Ag atom. However, their enhancement factors of the surface-enhanced Raman scattering without excitation light are less than 10, resulting from the static polarizability changes of the ground state. Surface enhanced Raman scattering (SERS) technique can be used in the early diagnosis of base pairs lesion to prevent genetic damage.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Surface enhanced Raman scattering can be used in early diagnosis of base pairs lesion to prevent genetic damage. ► The enhancement factor of SERS of uracil dimer is ascribed to static chemical enhancement from polarizability changes. ► The pre-resonance Raman spectrum of the U〈 〉UAg complexes at 315 nm, which are CT excitation resonance enhancement. ►The charge transfer resonant enhancement plays the major role in the molecule–metal system.