UPS and UV spectroscopies combined to position the energy levels of TiO2 anatase and rutile nanopowdersElectronic supplementary information (ESI) available: XRD patterns of TiO2 powders. Methodology of UPS calibration, background subtraction and absolute UPS measurement. UPS spectra of conducting substrates and the different TiO2 layers (rutile and anatase with various preparation methods). UV-Vis diffuse reflectance spectra. See DOI: 10.1039/c8cp04614j

• Main Authors: Maheu, Clément, Cardenas, Luis, Puzenat, Eric, Afanasiev, Pavel, Geantet, Christophe
• Format: Journal Article
• Published: 17.10.2018
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c8cp04614j

An accurate experimental determination of electronic structures in semi-conductor nanopowders is a challenging task. We propose here to combine UPS and UV-Vis spectroscopies in order to get the full description of the electronic band alignment of powder samples, TiO 2 rutile and anatase. For UPS measurements, two preparation methods, namely the dropping method and electrophoretic deposition, were used to prepare layers of titania powders on a conducting substrate, ITO or Ag. Both methods lead to comparable results, with a quantitative description of the energy levels from the valence band. Combining these results with the UV-Vis spectra of the same powders enables the determination of the absolute position of the valence band maximum and the conduction band minimum. Combined UPS-UV-Vis spectroscopy provides a better insight into the properties of a powdered material which can differ from single crystal model systems. It can also be used to predict the electronic transfer in mixed phase systems during photocatalytic processes. Positioning of absolute energy levels and the quantitative description of occupied levels obtained for TiO 2 nanopowders, combining UPS and UV-Vis spectroscopies.