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Nat Nanotechnol. 2008 Feb;3(2):106-11. doi: 10.1038/nnano.2008.2. Epub 2008 Feb 3.

Quantum size effect in TiO2 nanoparticles prepared by finely controlled metal assembly on dendrimer templates.

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Department of Chemistry, Faculty of Science and Technology, Keio University, Yokohama 223-8522, Japan.


The use of dendrimer templates to make metal-based nanoparticles of controlled size has attracted much interest. These highly branched macromolecules have well-defined structures that enable them to bind metal ions to generate precursors that can be converted into nanoparticles. We describe the sub-nanometre size control of both anatase and rutile forms of TiO2 particles with phenylazomethine dendrimers, leading to samples with very narrow size distributions. Such fine tuning is possible because both the number and location of metal ions can be precisely controlled in these templates. Quantum size effects are observed in the particles, and the energy gap between the conduction and valence bands exhibits a blueshift with decreasing particle size and is dependent on the crystal form of the material. The dependency of the bandgap energy on these factors is explained using a semi-empirical effective mass approximation.

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