Over the last decades, research on the interaction of DNA with nanosurfaces has become one of the most interesting case studies among all types of adsorbent/adsorbate systems due to its many applications in industrial and biological sciences. In this context, study of the adsorption of DNA bases on metal surfaces is a fundamental step towards understanding the interaction of the entire DNA molecule with these surfaces. Among the different bimetallic nanosurfaces, Au/Ag and Ag/Au nanosurfaces have important applications in the fields of catalysis, optics, biosensing and drug delivery. In the first part of this thesis, the adsorption of cytosine on the Au/Ag and Ag/Au bimetallic nanosurfaces has been investigated using density functional theory (DFT) in the scheme of the ONIOM and compared with its adsorption on pure Au and Ag nanosurfaces. The results show that the presence of Ag as sublayer in the Au/Ag nanosurface decreases the adsorption energy of the cytosine on the nanosurfaces and increases the vertical distance of the molecule from the surface compared to the pure Au surface, while the opposite trend is observed for the Au sublayer. It can also be deduced from quantum theory of atoms in molecules (QTAIM) and electron density difference analyses of the cytosine/nanosurfaces complexes that the Ag (Au) sublayer in the Au/Ag (Ag/Au) nanosurfaces increase (decrease) the charge transfer from the cytosine to the nanosurfaces compared to the corresponding pure nanosurfaces. In the second part of this thesis, absorption spectra of Au, Ag, Au/Ag, and Ag/Au nanosurfaces and cytosine/ nanosurfaces complexes has been calculated and compared to explore the effect of metallic structure of the sublayer and adsorbate on the intensity and position of the spectra maximum. In addition, the absorption lines responsible for the charge transfer from the cytosine to nanosurfaces due to the electronic excitation for each cytosine/nanosurface complex have been determined and the effect of sublayer on these electronic transitions has also been studied. Moreover, we have computed the IR spectra and surface-enhanced Raman spectroscopy (SERS) of cytosine on the nanosurfaces. The vibrational bands of the cytosine which in turn are sensitive to the metallic structure of sublayer are determined from the former, while the latter is used to specify the vibrational bands of the cytosine showing the intensity enhancement due to the charge transfer in the Raman spectrum for each nanosurface. The theoretical spectroscopic results presented in our research are very useful for the interpretation of experimental results, especially when the cytosine is adsorbed on nanosurfaces such as Ag, Au, and their bimetallic nanosurfaces. Finally, in the last part of this thesis, the effects of Au, Au/Ag, Ag, and Ag/Au nanosurfaces on the strength of interaction and hydrogen bonds between two adenine molecules have been studied. Our results show that the presence of sublayer in the Au/Ag and Ag/Au nanosurfaces decreases the interaction and adsorption energies of the dimer on these nanosurfaces compared to the pure counterparts. Also, in order to explore the net effects of nanosurfaces on the strength of the hydrogen bonds between two adenines, the topological parameters changes at the critical points of the two hydrogen bonds in the adenine dimer are used for the desired cytosine/nanosurfaces complexes. The presence of the Ag sublayer decreases the hydrogen bond strength in the dimer compared to the pure Au surface, while the opposite trend is seen for the Au sublayer. Overall, the results reveal that the Au/Ag and Ag/Au bimetallic nanosurfaces are more suitable substrates for the adenine self-assembly than the pure nanosurfaces.