Biomaterial−Biomolecule Interaction: DFT-D Study of Glycine Adsorption on Cr₂O₃

The adsorption of glycine, the smallest amino acid and building block of proteins, on a Cr 2 O 3 surface, taken as a model of stainless steel surfaces, was studied by means of GGA + U (on site Coulomb repulsion). The role of coverage on the adsorption mode and the self-assembly properties were explored. The dispersion contribution to the adsorption energies was also calculated. Glycine adsorbs at low and high coverage in the anionic form. The adsorption is driven by the formation of iono-covalent bonds with the Cr surface atoms. The most stable configurations correspond to maximization of the bonds (Cr−O and Cr−N), where the O or N atoms replace O atoms from the missing anionic plane above the terminal Cr plane. To maximize the bonds formation and minimize lateral repulsion, glycine lies parallel to the surface at low coverage and has a bent orientation at high coverage. The inclusion of dispersion forces strengthens this trend. At mean coverage under the ML, clusterization of high density domains may coexist with domains of lower coverage at the surface. At saturation, a glycinate monolayer with a 1:1 Gly:Cr ratio is formed.