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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∼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/lanl2dz 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 N3 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.

The structural and electronic properties of InN on Ce-stabilized zirconia (CeSZ) (111) substrates are investigated using firstprinciples calculations based on density functional theory with GGA + method. Surface energy calculations indicate that the structure of Ce-segregated surface is more energetically stable than that of Ce-segregation-free surface. Adsorption energies of indium and nitrogen atoms on both Ce-segregated and Ce-segregation-free CeSZ (111) surfaces at the initial growth stage have been studied. The results suggest that the first layer of InN films consists of a nitrogen layer, which leads to epitaxial relationships between InN (0001) // CeSZ (111) and InN [1120] // CeSZ [110]. In addition, density of states (DOS) analysis revealed that the hybridization effect plays a crucial role in determining the interface structure for the growth of InN on CeSZ (111) surfaces. Furthermore, adsorption energies of indium atoms on the nitrogen layer have also been evaluated in order to investigate the lattice polarity determination for InN films. It was found that an indium atom preferentially adsorbs at the center of three nitrogen atoms stacked on the CeSZ substrate, which results in the formation of In-polarity InN.