Surface force analysis of glycine adsorption on different crystal surfaces of titanium dioxide (TiO 2 ).

Surface force analysis with atomic force microscope (AFM) in which a single amino acid residue was mounted on the tip apex of AFM probe was carried out for the first time at the molecular level on titanium dioxide (TiO2 ) as a representative mineral surface for prebiotic chemical evolution reactions. The force analyses on surfaces with three different crystal orientations revealed that the TiO2 (110) surface has unique characteristics for adsorbing glycine molecules showing different features compared to those on TiO2 (001) and (100). To examine this difference, we investigated thermal desorption spectroscopy (TDS) and the interaction between the PEG cross-linker and the three TiO2 surfaces. Our data suggest that the different single crystal surfaces would provide different chemical evolution field for amino acid molecules.