[Back]

L. Liu, S. Li, H. Cheng, U. Diebold, A. Selloni:
"Growth and Organization of an Organic Molecular Monolayer on TiO_{2}: Catechol on Anatase (101)";
Journal of the American Chemical Society, 133 (2011), 7816 - 7823.

Anatase TiO2 is a widely used photocatalytic material,
and catechol (1,2-benzendiol) is a model organic sensitizer for dyesensitized
solar cells. The growth and the organization of a catecholate
monolayer on the anatase (101) surface were investigated with scanning
tunneling microscopy and density functional theory calculations.
Isolated molecules adsorb preferentially at steps. On anatase terraces,
monodentate (`D1´) and bidentate (`D2´) conformations are both
present in the dilute limit, and frequent interconversions can take place between these two species. A D1 catechol is mobile at room
temperature and can explore the most favorable surface adsorption sites, whereas D2 is essentially immobile. When a D1 molecule
arrives in proximity of another adsorbed catechol in an adjacent row, it is energetically convenient for them to pair up in nearestneighbor
positions taking a D2!D2 or D2!D1 con!guration. This intermolecular interaction, which is largely substrate mediated,
causes the formation of one-dimensional catecholate islands that can change in shape but are stable to break-up. The change
between D1 and D2 conformations drives both the dynamics and the energetics of this model system and is possibly of importance
in the functionalization of dye-sensitized solar cells.