Abstract

Density functional theory (DFT) is employed to examine the adsorption mechanism of DNA bases (adenine, guanine, cytosine, and thymine) on the gold surface using Au₆ cluster as model reactant. Geometries of resulting complexes are optimized using the PBE functional in conjunction with the cc-pVTZ-PP consistent-correlation pseudopotential basis set for gold and the cc-pVTZ basis set for the non-metals. The binding sites and energies, along with several quantum chemical indicators are also investigated at the same level of theory. The binding energies between Au₆ cluster and DNA bases are computed to be around 14–25 kcal/mol in gas-phase and slightly reduced to 10 – 20 kcal/mol in the water environment. Cytosine has the highest affinity with gold cluster, decreasing as follows cytosine > adenine  guanine > thymine. If a visible light with a frequency of Hz (500 nm) is applied, the time for the recovery of Au₆ from the complexes will be in the range of   (for thymine) to 10 (for cytosine) seconds at 298 K in water. In addition, the geometric structures of both the gold cluster and DNA bases are almost unchanged during the complexation. The gold cluster is found to benefit from a larger change of energy gap that could be converted to an electrical signal for the detection of these molecules. Current results could provide us with fundamentals for understanding the DNA bases absorption on gold nanoparticle surfaces at the atomic and molecular levels.