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Vapor-Phase Photo-Oxidation of Methanol Over Nanosize Titanium Dioxide Clusters Dispersed in MCM-41 Host Material Part 1: Synthesis and Characterization

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Abstract:

Nanosize clusters of titania were dispersed in mesoporous MCM-41 silica matrix with the help of the incipient wet-impregnation route, using an isopropanol solution of titanium isopropoxide as precursor. The clusters thus formed were of pure anatase phase and their size depended upon the titania loading. In the case of low (<15wt %) loadings, the TiO2 particles were X-ray and laser-Raman amorphous, confirming very high dispersion. These particles were mostly of ≤2 nm size. On the other hand, larger size clusters (2–15 nm) were present in a sample with a higher loading of ∼21 wt %. These particles of titania, irrespective of their size, exhibited an absorbance behavior similar to that of bulk TiO2. Powder X-ray diffraction, N2-adsorption and transmission electron microscopy results showed that while smaller size particles were confined mostly inside the pore system, the larger size particles occupied the external surface of the host matrix. At the same time, the structural integrity of the host was maintained even though some deformation in the pore system was noticed in the case of the sample having highest loading. The core level X-ray photoelectron spectroscopy results revealed a +4 valence state of Ti in all the samples. A positive binding energy shift and the increase of the width of Ti 2p peaks were observed, however, with the decrease in the particle size of supported titania crystallites, indicative of a microenvironment for surface sites that is different from that of the bulk.

Keywords: MCM-41; METHANOL OXIDATION; NANO-SIZE TITANIA; PHOTO-CATALYTIC OXIDATION

Document Type: Research Article

DOI: https://doi.org/10.1166/jnn.2005.113

Publication date: 2005-05-01

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  • Journal for Nanoscience and Nanotechnology (JNN) is an international and multidisciplinary peer-reviewed journal with a wide-ranging coverage, consolidating research activities in all areas of nanoscience and nanotechnology into a single and unique reference source. JNN is the first cross-disciplinary journal to publish original full research articles, rapid communications of important new scientific and technological findings, timely state-of-the-art reviews with author's photo and short biography, and current research news encompassing the fundamental and applied research in all disciplines of science, engineering and medicine.
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