Formation of the OOH(·) radical at steps of the boehmite surface and its inhibition by gallic acid: A theoretical study including DFT-based dynamics.

The ability of boehmite surface to stabilize reactive oxygen species (ROS) was investigated with density functional theory (DFT) calculations. We provide evidence that the O2(·-)radical is stabilized at the AlOOH boehmite terrace defect-free surface, and that step favors the formation of the OOH(·) radical without activation energy required. These tendencies are confirmed when considering the explicit presence of water solvent. We propose that gallic acid (GA), a non-expensive, non-toxic, natural product and radical scavenger, may form a full layer on the (101) stepped boehmite surface. The quenching of O2- to OOH(·) reaction on the GA-functionalized boehmite surface is investigated. It is shown that gallic acid passivates the surface and that the formation of the OOH(·) radical is consequently inhibited. The interaction of the GA-functionalized boehmite surface with water mimicking the body fluid is also investigated by means of DFT-based molecular dynamics simulations at room temperature. Hydrogen bonds between the functionalized GA layer and the immediate interfacial water are characterized.