The Effect of Surface Electronic Structure on the Bioactivity of Neutral Dopant Si, Ge, and Sn on TiO₂ (110): A DFT Study

In this paper, first principles calculations based on density functional theory were used to study the electronic properties and adsorption behavior of modified rutile surfaces with neutral element dopants (Si, Ge, Sn). The results showed that Sn doped surface has the smallest work function (7.07 eV) and Ge doped surface has the lowest conduction band edge (1.28 eV). Furthermore, the adsorption behavior of H₂O and Arg-Gly-Asp (RGD) molecules on modified rutile surfaces was calculated to estimate the biocompatibility of modified dental implant surfaces. For the purpose of simulating the real solution environment, the free energy of solvation for adsorbates, calculated by Gaussian 09 program code, was taken into account. The results of the adsorption calculations of H₂O indicate that Sn doped surface has a more negative adsorption energy (−3.15 eV) and a higher charge transfer (−0.1) than any other modified surface, which is consistent with its low work function. The results of the adsorption calculations of Arg-Gly-Asp demonstrate that Ge doped surface also has a shorter distance (1.95 Å) between Ti atom and O atom in RGD, which is similar with the partial density of states results. All of the results show that the electronic structure of an implant surface has a significant influence on its bioactivity and is also useful for the design of modification methods on dental implant surfaces.