SERS study and DFT simulation of the interaction of cytosine with copper electrode

In order to obtain a deeper insight into the interaction between cytosine and copper electrode, a surface-enhanced Raman scattering (SERS) study and density functional theory (DFT) simulation have been used. The experimental result shows that a decrease of relative intensity of the band at around 1315 cm(-1) is accompanied by a considerable increase of relative intensity of the bands in the 1490 similar to 1600 cm(-1) region when the potential is below -0.7 V, and it is explained by the chemical effect (CE). Simultaneously, the geometry and Raman spectra of neutral and cationic Cu-cytosine complexes are calculated and simulated using the B3LYP/lan12dz basis. The simulation shows that the relative intensities of Raman spectra depend strongly on the molecular active sites involved in the interaction between the copper electrode and the cytosine molecule. Combining the experimental results with theoretical calculations, we conclude that the adsorptive orientation of cytosine on the copper electrode occurs on the N(3) site and the carbonyl site when the potential is above and below -0.7 V, respectively. This study also indicates that a combination of SERS and DFT simulations is a valuable tool for studying interactions of biomolecules with metal.