Structural and electronic properties of sol-gel titanium oxides studied by X-ray absorption spectroscopy

V Luca, S Djajanti, Russell Francis Howe

Research output: Contribution to journalArticle

192 Citations (Scopus)

Abstract

X-ray absorption spectroscopy (XAS) has been used to study the local Ti environment in titania xerogel samples containing nanoparticles of different sizes. The xerogels were prepared by hydrolysis of titanium isopropoxide followed by peptization with HNO3 and size control was achieved through calcination in air at different temperatures. An amorphous precipitate obtained by hydrolysis of titanium isopropoxide prior to peptization with HNO3 has also been studied. The X-ray absorption near edge structure (XANES) of the precipitate possesses a characteristic preedge that is dominated by a transition designated as A2 at 4970.7 eV, and assigned to five coordinate Ti. This A2 component is detected in all of the studied xerogels. Its intensity decreases as the surface-to-volume ratio of the titania particles decreases, suggesting that it is associated with surface layers of the anatase particles. Other changes observed in the XANES of the xerogels as a function of particle size include broadening of 1s --> np transitions in the postedge region. EXAFS shows that the smallest particles contain Ti in distorted coordination with contracted Ti-O bonds and probably reduced coordination number.

Original languageEnglish
Pages (from-to)10650-10657
Number of pages8
JournalThe Journal of Physical Chemistry B
Volume102
Issue number52
Early online date8 Dec 1998
DOIs
Publication statusPublished - 24 Dec 1998

Keywords

  • conduction-band electrons
  • optical electrochemistry
  • coordination chemistry
  • semiconductor-films
  • size quantization
  • silicate-glasses
  • TIO2 electrodes
  • colloidal TIO2
  • K edges
  • anatase

Cite this

Structural and electronic properties of sol-gel titanium oxides studied by X-ray absorption spectroscopy. / Luca, V ; Djajanti, S ; Howe, Russell Francis.

In: The Journal of Physical Chemistry B, Vol. 102, No. 52, 24.12.1998, p. 10650-10657.

Research output: Contribution to journalArticle

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abstract = "X-ray absorption spectroscopy (XAS) has been used to study the local Ti environment in titania xerogel samples containing nanoparticles of different sizes. The xerogels were prepared by hydrolysis of titanium isopropoxide followed by peptization with HNO3 and size control was achieved through calcination in air at different temperatures. An amorphous precipitate obtained by hydrolysis of titanium isopropoxide prior to peptization with HNO3 has also been studied. The X-ray absorption near edge structure (XANES) of the precipitate possesses a characteristic preedge that is dominated by a transition designated as A2 at 4970.7 eV, and assigned to five coordinate Ti. This A2 component is detected in all of the studied xerogels. Its intensity decreases as the surface-to-volume ratio of the titania particles decreases, suggesting that it is associated with surface layers of the anatase particles. Other changes observed in the XANES of the xerogels as a function of particle size include broadening of 1s --> np transitions in the postedge region. EXAFS shows that the smallest particles contain Ti in distorted coordination with contracted Ti-O bonds and probably reduced coordination number.",
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N2 - X-ray absorption spectroscopy (XAS) has been used to study the local Ti environment in titania xerogel samples containing nanoparticles of different sizes. The xerogels were prepared by hydrolysis of titanium isopropoxide followed by peptization with HNO3 and size control was achieved through calcination in air at different temperatures. An amorphous precipitate obtained by hydrolysis of titanium isopropoxide prior to peptization with HNO3 has also been studied. The X-ray absorption near edge structure (XANES) of the precipitate possesses a characteristic preedge that is dominated by a transition designated as A2 at 4970.7 eV, and assigned to five coordinate Ti. This A2 component is detected in all of the studied xerogels. Its intensity decreases as the surface-to-volume ratio of the titania particles decreases, suggesting that it is associated with surface layers of the anatase particles. Other changes observed in the XANES of the xerogels as a function of particle size include broadening of 1s --> np transitions in the postedge region. EXAFS shows that the smallest particles contain Ti in distorted coordination with contracted Ti-O bonds and probably reduced coordination number.

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KW - conduction-band electrons

KW - optical electrochemistry

KW - coordination chemistry

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KW - size quantization

KW - silicate-glasses

KW - TIO2 electrodes

KW - colloidal TIO2

KW - K edges

KW - anatase

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