Surface hydroxy groups are known to play a significant role in the photocatalytic behavior of TiO2. The molecular or dissociative character of H2O adsorption on titania is strongly affected by the local surface structure, but dissociation, producing −OH, should prevail on surface sites with a high degree of coordinative unsaturation. Here we report an IR investigation of hydroxy groups on low coordination sites of TiO2 P25 (Degussa), a commercial titania powder considered a staple in the field of heterogeneous photocatalysis. The presence of coordinatively defective surface terminations well agrees with the roughness of the border of TiO2 particles observed by high resolution transmission electron microscopy. Furthermore, IR spectra of adsorbed CO were used to probe the Lewis acidity of surface Ti4+ ions exposed after the removal of water molecules and hydroxy groups. Evidence for two additional types of surface cationic sites with respect those reported in the literature was 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.

Integrated studies of CO on truncated bipyramidal TiO 2 anatase nanoparticles mainly exposing smooth (101) surfaces provide the missing link between TiO 2 single crystals and commercial TiO 2 nanopowders with complex morphology. The synergy among high resolution transmission electron microscopy, IR spectroscopy and modeling correlates adsorbed CO stretching frequency to anatase surface type, and reveals how disorder of the adsorbed CO layer affects CO/TiO 2 IR bands.