UV induced hydrophilicity
Un article de Surface du verre et interfaces.
Ramzi Jribi(PhD 2005-2008) - Etienne Barthel, Muriel Beauvais, Davy Dalmas & Elin Sondergard
Environmental concerns have recently spurred a quest for materials that stay clean, such as TiO2, when subjected to the combined action of sunlight irradiation and exposure to rain. However, the fundamental mechanism that governs the self-cleaning properties of TiO2 still needs to be elucidated. TiO2 is known to be photo-catalytic as well as to decompose organic adsorbents, but these properties do not explain its capacity to eliminate mineral contaminants. We have demonstrated that UV irradiated (hydrophilic) TiO2 layers are non-adhesive in the presence of water, thus preventing adhesion of mineral particles. Surface forces measurements by Atomic Force Microscopy reveal the presence of an additional short range repulsive force, which screens the van der Waals attraction forces, while long range interactions are preserved. This additional short range force does not originate from UV induced trapping of surface charges or OH group creation, as we demonstrate by second harmonic generation and ambient pressure X-ray photo-electron spectroscopy investigations. This short range repulsive force, which appears to be intrinsic to the clean TiO2 surface, is certainly a key phenomenon for a strong self-cleaning capacity.
Collaborations
- Hendrik Bluhm, In situ high pressure X-ray Photoemission Spectroscopy, Advanced Light Source, Berkeley, California, USA
- Patrick Kölsch, Non-linear Optics: Second Harmonic Generation, Institute of applied physical chemistry, Ruprecht-Karls-University, Heidelberg, Germany
- Frédéric Ott, Alain Menelle, Fabrice Cousin, Adsorption isotherm measurements with grazing incidence neutron scattering, Léon Brillouin Laboratery, Saclay, France
Recent Publications
- UV-irradiation suppresses adhesion on TiO2, R. Jribi, E. Barthel, H. Bluhm, M. Grunze, P. Koelsch, D. Verreault, E. Søndergård, J. Phys. Chem. C 113 (2009) 8273-8277