Tautomerism of thymine on gold and silver nanoparticle surfaces: surface-enhanced Raman scattering and density functional theory calculation study

Tautomerism of thymine on gold and silver nanoparticle surfaces has been comparatively analyzed by means of surface-enhanced Raman scattering (SERS). The intensities of the ring breathing mode of thymine indicated that the N3-deprotonated tautomer should be about 10 times more abundant than the N1-deprotonated tautomer on Ag surfaces whereas almost no N1-deprotonated tautomer was observed for Au under our experimental condition. The density functional theory (DFT) calculation was performed at the levels of B3LYP and MP2 to estimate the energetic stability of the N3 and N1-deprotonated tautomers on the surfaces. The N3-deprotonated tautomer was predicted to be more favorable on Au than on Ag from the DFT calculation as consistent with our SERS spectra.