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

Nature Nanotechnology volume 3, pages 106–111 (2008)Cite this article

Abstract

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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Figure 1: Sub-nanometre size control and synthetic strategy for Q-size TiO2 using the DPA G4 template.
Figure 2: Changes in UV-vis spectra of DPA G4 during the addition of Ti(acac)Cl3.
Figure 3: Stepwise radial complexation of Ti(acac)Cl3 into DPA G4.
Figure 4: Size measurements for TiO2 obtained using the DPA G4 template.
Figure 5: Bandgap measurements for 6TiO2 (green), 14TiO2 (red) and 30TiO2 (blue).

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Acknowledgements

We thank Y. Einaga, N. Yoshioka and H. Imai for useful discussions. This work was partially supported by CREST from the Japan Science and Technology Agency, Grants-in-Aid for Scientific Research (No. 19205020) and the 21st Center of Excellence (COE) Program (Keio-LCC) from Ministry of Education, Culture, Sports, Science and Technology (MEXT).

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

    Norifusa Satoh, Toshio Nakashima, Kenta Kamikura & Kimihisa Yamamoto

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  1. Norifusa Satoh
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All authors conceived and designed the experiments. N.S. and K.Y. co-wrote the paper.

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Correspondence to Kimihisa Yamamoto.

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Satoh, N., Nakashima, T., Kamikura, K. et al. Quantum size effect in TiO2 nanoparticles prepared by finely controlled metal assembly on dendrimer templates. Nature Nanotech 3, 106–111 (2008). https://doi.org/10.1038/nnano.2008.2

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