Probing the Electronic Structure and Band Gap Evolution of Titanium Oxide Clusters (TiO2)n- (n=1-10) Using Photoelectron Spectroscopy

Journal Article · Wed Mar 14 04:00:00 EDT 2007 · Journal of the American Chemical Society, 129(10):3022-3026

DOI:https://doi.org/10.1021/ja068601z· OSTI ID:918463

Zhai, Hua-jin; Wang, Lai S

TiO2 is a wide-band gap semiconductor and it is an important material for photocatalysis. Here we report an experimental investigation of the electronic structure of (TiO2)n clusters and how their band gap evolves as a function of size using anion photoelectron spectroscopy (PES). PES spectra of (TiO2)n– clusters for n = 1–10 have been obtained at 193 (6.424 eV) and 157 nm (7.866 eV). The high photon energy at 157 nm allows the band gap of the TiO2 clusters to be clearly revealed up to n = 10. The band gap is observed to be strongly size-dependent for n < 7, but it rapidly approaches the bulk limit at n = 7 and remains constant up to n = 10. All PES features are observed to be very broad, suggesting large geometry changes between the anions and the neutral clusters due to the localized nature of the extra electron in the anions. The measured electron affinities and the energy gaps are compared with available theoretical calculations. The extra electron in the (TiO2)n– clusters for n > 1 appears to be localized in a tricoodinated Ti atom, creating a single Ti3+ site and making these clusters ideal molecular models for mechanistic understanding of TiO2 surface defects and photocatalytic properties.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 918463
• Report Number(s): PNNL-SA-53623; 20901; KC0301020
• Journal Information: Journal of the American Chemical Society, 129(10):3022-3026, Journal Name: Journal of the American Chemical Society, 129(10):3022-3026 Journal Issue: 10 Vol. 129; ISSN JACSAT; ISSN 0002-7863
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
ANIONS
DEFECTS
ELECTRONIC STRUCTURE
ELECTRONS
Environmental Molecular Sciences Laboratory
GEOMETRY
MOLECULAR MODELS
PHOTOCATALYSIS
PHOTOELECTRON SPECTROSCOPY
PHOTONS
SPECTRA
TITANIUM OXIDES