Location Of Hole And Electron Traps On Nanocrystalline Anatase TiO2

Journal Article · Thu May 17 04:00:00 EDT 2012 · Journal of Physical Chemistry C

DOI:https://doi.org/10.1021/jp301680d· OSTI ID:1043107

Mercado, Candy C; Knorr, Fritz J; McHale, Jeanne L; Usmani, Shirin M; Ichimura, Andrew S; Saraf, Laxmikant V

The defect photoluminescence from TiO2 nanoparticles in the anatase phase is reported for nanosheets which expose predominantly (001) surfaces, and compared to that from conventional anatase nanoparticles which expose mostly (101) surfaces. Also reported is the weak defect photoluminescence of TiO2 nanotubes, which we find using electron back-scattered diffraction to consist of walls which expose (110) and (100) facets. The nanotubes exhibit photoluminescence that is blue-shifted and much weaker than that from conventional TiO2 nanoparticles. Despite the preponderance of (001) surfaces in the nanosheet samples, they exhibit photoluminescence similar to that of conventional nanoparticles. We assign the broad visible photoluminescence of anatase nanoparticles to two overlapping distributions: hole trap emission associated with oxygen vacancies on (101) exposed surfaces, which peaks in the green, and a broader emission extending into the red which results from electron traps on under-coordinated titanium atoms, which are prevalent on (001) facets. The results of this study suggest how morphology of TiO2 nanoparticles could be optimized to control the distribution and activity of surface traps. Our results also shed light on the mechanism by which the TiCl4 surface treatment heals traps on anatase and mixed-phase TiO2 films, and reveals distinct differences in the trap-state distributions of TiO2 nanoparticles and nanotubes. The molecular basis for electron and hole traps and their spatial separation on different facets is discussed.

• 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: 1043107
• Report Number(s): PNNL-SA-88153; 44706; KP1704020
• Journal Information: Journal of Physical Chemistry C, Journal Name: Journal of Physical Chemistry C Journal Issue: 19 Vol. 116; ISSN 1932-7447
• Country of Publication: United States
• Language: English

Related Subjects

77 NANOSCIENCE AND NANOTECHNOLOGY
ATOMS
DEFECTS
DIFFRACTION
DISTRIBUTION
ELECTRONS
Environmental Molecular Sciences Laboratory
MORPHOLOGY
NANOTUBES
OXYGEN
PHOTOLUMINESCENCE
SURFACE TREATMENTS
TITANIUM OXIDES
VACANCIES