Interaction between polysaccharide monomer and SiO2/Al2O3/CaCO3 surfaces: A DFT theoretical study

In the present study, the interaction between a model polysaccharides monomer beta-D-glucopyranose with different mineral solid surfaces, including hydroxylated (0 0 1) surface of SiO2, (0 0 0 1) surface of Al2O3 and (1 0 4) surface of CaCO3, were explored by theoretical calculations based on Density Functional Theory (DFT) under periodic boundary conditions. The adsorption geometry of the beta-D-glucopyranose monomer (GM) at different solid surface and the interaction energies were analyzed in detail, and the interaction mechanism was determined via electron density differences iso-surface, Mulliken charge, as well as projected density states (PDOS) analysis. Very strong interaction was found between GM and Al2O3 (0 0 0 1) surface, which was mainly attributed to the formation of bridging Al-O bonds and H-bonds. There was the bonding between H-1s and O-2p orbitals for the formed hydrogen bonds and hybridization between O-p states and Al-d states for the bridging Al-O bonds. The interaction between GM and CaCO3 (1 0 4) surface was mainly attributed to the electrostatic interaction and hydrogen bonded interaction, and was fairly strong, too. But there was only hydrogen bonds between GM and SiO2 surface, which was relative weak. In all the three adsorbed systems, significant charge redistribution was observed which contributed to the interaction between them, though little electron transferred between them. The finding is very meaningful for providing theoretical direction in proceeding sufficient application of diverse kind of natural sugar-based functional substances in many fields.