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Multicolour photochromism of TiO2 films loaded with silver nanoparticles

Nature Materials volume 2, pages 2931 (2003) | Download Citation



Photochromic materials, which change their colours reversibly in response to light, can be applied to smart windows, displays and memories1,2,3. Conventional photochromic materials respond in a monochromatic way, so that multicolour photochromism has required several different materials or filters combined appropriately. If multicolour photochromism could be achieved with a simple material, photochromic devices would be find a greater number of applications, including a rewritable colour copy paper or electronic paper4 and a high-density multi-wavelength optical memory. Here we report multicolour photochromism of TiO2 films loaded with silver nanoparticles by photocatalytic means. Its colour, initially brownish-grey, changes under monochromatic visible light to almost the same colour as that of the light; the apparently uniform Ag–TiO2 film can be almost any colour. Behaviour similar to persistent hole-burning effects5,6 is also observed. The colour reverts to brownish-grey under ultraviolet light, and these processes are repeatable.

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We thank O. Sato, H. Tsunakawa, T. Itoh and Y. Kakegawa for help with experiments. This work was supported in part by a Grant-in-Aid for Scientific Research on Priority Areas (Area No. 417 for T.T., Y.K. and A.F.) from the Ministry of Education, Science, Sports and Culture of Japan.

Author information


  1. Department of Applied Chemistry, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan

    • Yoshihisa Ohko
    • , Tsuyoshi Fujii
    • , Kenji Naoi
    •  & Akira Fujishima
  2. PRESTO, Japan Science and Technology Corporation (JST), 4-1-8 Honcho, Kawaguchi-shi, Saitama 332-0012, Japan

    • Yoshihisa Ohko
  3. Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan

    • Tetsu Tatsuma
  4. Kanagawa Academy of Science and Technology, KSP Bldg. East 412, 3-2-1 Sakado, Takatsu-ku, Kawasaki-shi, Kanagawa 213-0012, Japan

    • Chisa Niwa
  5. Department of Urology, School of Medicine, University of Yokohama City, 3-9 Fukuura, Kanazawa-ku, Yokohama-shi, Kanagawa 236-0004, Japan

    • Yoshinobu Kubota


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The authors declare no competing financial interests.

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Correspondence to Akira Fujishima.

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