Journal
JOURNAL OF SOLID STATE CHEMISTRY
Volume 183, Issue 10, Pages 2451-2455Publisher
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.jssc.2010.08.018
Keywords
Micro-Raman spectroscopy; Anatase; Carbon nanotube composites; Hydrogen sensors
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Titanium oxide/carbon nanotubes-based nanocomposites (TiO2/CNTs, prepared by sal-gel method, and 2%Pt/TiO2/CNTs, obtained by wetness impregnation of the TiO2/CNTs base material with a solution of platinum acetylacetonate) have been recently used as active layer in hydrogen sensing devices at near room temperature, obtaining quite different responsiveness. The microstructure of these hybrid materials is here systematically investigated by micro-Raman spectroscopy at 2.41 eV. The results show that regardless of the nominal C/Ti molar ratio (3.6 or 17.0) only the anatase phase of titania is formed. Theoretical calculations demonstrate that phonon confinement is fully responsible for the large blue-shift (similar to 10 cm(-1)) and broadening (similar to 20 cm(-1)) of the lowest-frequency Raman mode with respect to bulk anatase. The average size (4.3-5.0 nm) of TiO2 crystallites, resulting from Raman spectra fitting, is in excellent agreement with those inferred from transmission electron microscopy and X-ray diffraction measurements. (C) 2010 Elsevier Inc. All rights reserved.
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