Spectroscopical characterization of TiO2 powders prepared from stable colloidal solutions

Monticone, S.; Tufeu, R.; Kanaev, Andreï

doi:10.1016/s0009-2614(98)00953-1

Cited by 12 publications

(12 citation statements)

References 18 publications

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“…This procedure is presented in Figure . The obtained value of E g is in agreement with the earlier published value in ref . AO of this solid phase is situated 0.42 and 0.62 eV higher than that of the anatase and rutile phases of TiO 2 .…”

Section: Resultssupporting

confidence: 92%

“…Moreover, the spectrum exhibits a long exponential tail below 3.6 eV indicating intense subband transitions. We assign the nuclei and precipitated powders to the solid in the polymer or “oxo” phase, which serves as a precursor of the anatase crystalline phase of TiO 2 and which can be transformed to the last by thermal treatment at 400 °C 6 Determination of the AO value of the solid in the “oxo” or polymer phase. …”

Section: Resultsmentioning

confidence: 99%

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Nucleation Stage in the Ti(OPrⁱ)₄ Sol−Gel Process

et al. 2001

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A spectroscopic study of the initial stage of the Ti(OPr i )4 sol−gel process has been carried out. We have observed that the primary hydrolysis/condensation reaction is complete at low water concentration. At times shorter that the induction time, the reaction results in creation of nanosize nuclei. The most important finding is that the total nuclei mass, which appears almost instantaneously during the stage of mixing, is conserved throughout the process: the particles grow by nucleus agglomeration. The hydrolysis ratio H ≤ 1 is sufficient for nucleus creation; H > 1 is needed for particle growth. The initial reagent mixing seems to be the key stage of the process.

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Section: Resultssupporting

confidence: 92%

Section: Resultsmentioning

confidence: 99%

Nucleation Stage in the Ti(OPrⁱ)₄ Sol−Gel Process

et al. 2001

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“…Thus, TiO 2 "particles" in the sub-nm size range are better described as titanium ox-oorganocomplexes. Measurements of dynamic light scattering of TiO 2 dispersions prepared with a similar protocol to that used in this work showed that the particles diameter is 4 nm [14]. Therefore, the radius of the particles prepared in this work is expected to be approximately 2 nm.…”

Section: Resultsmentioning

confidence: 73%

“…The band gap, E g , of TiO 2 is 3.19 eV in the anatase form and 3.0 eV for the rutile polymorph. As anatase is the most usual TiO 2 form obtained from the sol-gel process [14,15], the transition 3 →X 1b [7] that occurs at 3.26 eV corresponds to the E g value of the particles prepared in this work.…”

Section: Resultsmentioning

confidence: 92%

Characterization of TiO2 Nanoparticles in Langmuir-Blodgett Films

Coutinho

Barbosa

2006

J Fluoresc

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In this work we have synthesized TiO2 nanoparticles, using either a sol-gel base catalysed process in the interior of CTAB reversed micelles (TiO2 CTAB sol), or the neutralization of a TiO2/H2SO4 solution in the interior of AOT reversed micelles. From the absorption and emission data of the TiO2 nanoparticles it is possible to conclude that in the sol-gel route there remains alkoxide groups in the structure, originating transitions lower than the energy gap of TiO2 semiconductor. These transitions disappear in the neutralization procedure, where the alkoxide groups are absent in the structure. We have assigned the observed indirect and direct optical transitions according to the anatase band structure. TiO2 Langmuir-Blodgett (LB) films were prepared either by direct deposition of titanium isopropoxide or by deposition of the TiO2 CTAB sol. These films showed photoluminescence, which was attributed to band-gap emission and to surface recombination of defect states.

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“…Actually ZnO follows a general behavior common for semiconducting metal oxides and particularly TiO 2 . 44,45 Indeed, TiO 2 does not emit photoluminescence except for very small nanoparticles of size smaller than a few nanometres.…”

Section: Photoluminescence Of Mof-5mentioning

confidence: 99%