Journal
PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE
Volume 209, Issue 3, Pages 537-544Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/pssa.201127456
Keywords
hydrothermal synthesis; nanocrystals; photoluminescence; tungsten oxides
Funding
- Fundamental Research Funds for the Central Universities [ZYGX2009J046, ZYGX2009X007]
- Sichuan Young Scientists Foundation [2010JQ0006]
- NSAF Joint Foundation of China [11076008]
- Royal Society of Edinburgh
- Carnegie Trust Founding
- Royal Academy of Engineering-Research Exchanges with China and India in UK
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Crystals of hexagonal tungsten oxides (hex-WO3) have been synthesized using hydrothermal method at 150 degrees C, assisted by the capping reagent of ammonium tartrate (AT). The XRD and EDX results reveal that the lattice distortion exists in all the samples, possibly due to the defects and the intercalation of the residual sodium ions. Different crystal shapes including plate-like, urchin-like, and particle structures were obtained by varying concentration of AT and pH values in the precursor solution. Beside the absorption action of the NH4+ and Na+ ions, the capping effect can be reinforced by the hydrogen bonding from the tartrate groups in the crystallization process. The bandgap energies were modulated by the size of the nanostructured hex-WO3 crystals due to quantum confinement effect, which increases from 2.74 to 3.04 eV. Based on the analysis of the photoluminescence and X-ray photoelectron spectroscopy, the enhancement of the blue emission of the nanocrystals is assigned as a result of a complex of the local intercalation of the residual sodium ions and the oxygen vacancies or defects. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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