Multicolour photochromism of TiO2 films loaded with silver nanoparticles



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.

  • Subscribe to Nature Materials for full access:



Additional access options:

Already a subscriber?  Log in  now or  Register  for online access.


  1. 1.

    & Photochromic silicate glasses sensitized by silver halides. Science 144, 150–154 (1964).

  2. 2.

    , & Photochromism induced in an electrolytically pretreated MoO3 thin film by visible light. Nature 355, 624–626 (1992).

  3. 3.

    Diarylethenes for memories and switches. Chem. Rev. 100, 1685–1716 (2000).

  4. 4.

    The electronic paper chase. Sci. Am. 285, 38–43 (2001).

  5. 5.

    (ed.) Persistent Spectral Hole-Burning: Science and Applications (Springer, Berlin, 1988).

  6. 6.

    & Room-temperature hole-burning and sublinear hole-growth dynamics in an Sm2+-doped aluminosilicate glass. J. Non-Cryst. Solids 297, 113–119 (2002).

  7. 7.

    & Photocatalytically deposited silver nanoparticles on mesoporous TiO2 films. Langmuir 16, 2398–2400 (2000).

  8. 8.

    , , , , & Characterization and photocatalytic activity in aqueous medium of TiO2 and Ag–TiO2 coatings on quartz. Appl. Catal. B 13, 219–228 (1997).

  9. 9.

    , & Intensity-dependent photobleaching through bulk oxide glass containing silver particles. J. Appl. Phys. 84, 6457–6459 (1998).

  10. 10.

    Absorption of colloidal silver in KCl. Z. Phys. 215, 113–120 (1968).

  11. 11.

    , , , & Experimental test of the Mie theory for microlithographically produced silver spheres. Phys. Rev. B 35, 2151–2154 (1987).

  12. 12.

    Optical properties of small silver particles. J. Chem. Phys. 42, 414–417 (1965).

  13. 13.

    et al. Photoinduced conversion of silver nanospheres to nanoprisms. Science 294, 1901–1903 (2001).

  14. 14.

    , , , & Shape effects in plasmon resonance of individual colloidal silver nanoparticles. J. Chem. Phys. 116, 6755–6759 (2002).

  15. 15.

    & Effect of particle shape on the spectral absorption of colloidal silver in gelatin. J. Chem. Phys. 48, 3297–3304 (1968).

Download references


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


  1. Search for Yoshihisa Ohko in:

  2. Search for Tetsu Tatsuma in:

  3. Search for Tsuyoshi Fujii in:

  4. Search for Kenji Naoi in:

  5. Search for Chisa Niwa in:

  6. Search for Yoshinobu Kubota in:

  7. Search for Akira Fujishima in:

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Akira Fujishima.