This paper is an extension of previous work devoted to the characterization of platelet-like hydroxyapatite (HA) nanoparticles constituted by a crystalline core coated by an amorphous surface layer 1-2 nm thick (Bertinetti et al. J. Phys. Chem. C. 2007, 111, 4027-4035). By increasing the preparation temperature, the platelet morphology was retained but HA nanoparticles exhibited a higher degree of crystallinity (evaluated by X-ray diffractometry). High-resolution transmission electron microscopy revealed that, in this case, the crystalline order was extended up to the particles' surfaces, which were of the ( 010), (100), and (001) types. IR spectroscopy was used to investigate the surface hydration of both materials, in terms of adsorbed H 2 O molecules and surface hydroxy groups, as well as the Lewis acidity of surface cations, by removing water and adsorbing CO. For both features, strong similarities between amorphous and crystalline surfaces were found.

In situ IR and mass spectrometry evidence for the catalytic formation on SiO2 and TiO2 surfaces of glycine oligomers (poly‐Gly) up to 16 units long by successive feeding with monomers from the vapor phase is presented. Parallel experiments carried out on hydroxyapatite resulted in the unreactive adsorption of Gly, thus indicating that the oligomerization was specifically catalyzed by the surfaces of SiO2 and TiO2. Furthermore, the poly‐Gly moved on the surface when contacted with H2O vapor and formed self‐assembled aggregates containing both helical and β‐sheet‐like structural motifs. These results indicate that polypeptides formed by the condensation of amino acids adsorbed on a mineral surface can evolve into structured supramolecular assemblies.

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