title: Surface features of TiO2 nanoparticles: combination modes of adsorbed CO probe the stepping of (101) facets.
abstract: Integrated studies of CO adsorption on TiO2 materials of different morphology and surface complexity identify, for the first time, frustrated translational CO modes by detecting their combination with the CO stretching mode (νCO). All the considered materials exhibit IR spectra with low-intensity bands in the 2235-2205 cm(-1) range, a region where components due to strong Lewis acid Ti(4+) sites may be present as well. These observations lead to a powerful method for associating high-wavenumber bands to TiO2 surface features and interpreting IR spectra of drastically complex/defective TiO2 materials. The proposed band assignment is based on vibrational analyses of CO-TiO2 theoretical models, indicating that the frustrated translational mode with frequency in the 30-50 cm(-1) range involved in the observed combination bands is perpendicular to the Ti(4+) rows. Our results reveal that this low-energy CO mode is much more sensitive than νCO in probing the TiO2 surface topography, and that its higher-energy components can be specifically associated with the presence of steps on the (101) faces. In a broader perspective, the frustrated translational CO mode surface sensitivity could become a key tool for detecting specific defective sites on TiO2 surfaces.
authors.affiliation: Department of Chemistry and Interdepartmental Centre of Excellence Nanostructured Interfaces and Surfaces-NIS, University of Torino, via P. Giuria 7, 10125 Torino, Italy.
authors.forename: Chiara
authors.initials: C
authors.lastname: Deiana
authors.forename: Gloria
authors.initials: G
authors.lastname: Tabacchi
authors.forename: Valter
authors.initials: V
authors.lastname: Maurino
authors.forename: Salvatore
authors.initials: S
authors.lastname: Coluccia
authors.forename: Gianmario
authors.initials: G
authors.lastname: Martra
authors.forename: Ettore
authors.initials: E
authors.lastname: Fois
mesh_terms: D000327:Adsorption; D002248:Carbon Monoxide / Q000737:chemistry*; D053758:Nanoparticles / Q000737:chemistry*; D010316:Particle Size; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*
chemical_list: C009495:titanium dioxide; D002248:Carbon Monoxide; D014025:Titanium