Research ArticleChemistry

TiO2 metasurfaces: From visible planar photonics to photochemistry

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Science Advances  01 Nov 2019:
Vol. 5, no. 11, eaax0939
DOI: 10.1126/sciadv.aax0939
  • Fig. 1 The properties of the black TiO2 film.

    (A) Schematic picture for the transition process between conventional TiO2 and black TiO2. The insets show the corresponding microscope images of TiO2 films. (B) Dashed, solid, and dash-dotted lines are the absorption spectra of TiO2 film before and after 4-min H+ ion implantation and the recovered TiO2 film. (C) and (D) show the refractive index n and light extinction coefficient k as a function of ion implantation time.

  • Fig. 2 The conventional TiO2 metasurfaces.

    (A) Top-view SEM images of TiO2 metasurfaces. Scale bars, 200 nm. The insets show the corresponding structural colors under a bright-field microscope. (B) Measured (solid lines) and numerically calculated (dashed lines) reflection spectra. From bottom to top, the lattice size decreases from 400 to 380, 370, 350, 330, 320, and 300 nm. The gap is kept at w = 70 nm. The insets are the recorded (left) and calculated (right) structural colors. (C) Corresponding structural colors of 15 metasurfaces in the CIE 1931 map.

  • Fig. 3 The erased structural colors of TiO2 metasurfaces and optical encryption.

    (A) Reflection spectra of three TiO2 metasurfaces with l = 330 nm, l = 280 nm, and l = 230 nm before implantation (dashed lines), after 1-min ion implantation (dotted lines), after 4-min ion implantation (dash-dotted lines), and lastly recovered with O implantation (solid lines). The insets were the corresponding structural colors under a bright-field microscope. (B) Reversible transition of the TiO2 metasurfaces as a function of transition rounds. No obvious degradation can be observed. (C) Color transitions of total 15 TiO2 metasurfaces with different lattice sizes. (D) Corresponding transitions in the International Commission on Illumination (CIE) 1931 map. (E) Top-view SEM image of the encoded information and the background. The information “COLOR” is guided with dashed lines. Scale bar, 10 μm. (F) Displayed color image under a bright-field microscope. (G) Reversible color switch before and after H+ ion implantation and O implantation for several rounds. a.u., arbitrary units.

  • Fig. 4 The black TiO2 metasurface–based photochemistry.

    (A) Schematic picture of the photoreduction of Ag nanoparticles in solutions. (B) Reflection spectrum of the TiO2 metasurface. The inset is the top-view SEM image. Scale bar, 400 nm. (C) Absorption spectrum of the black TiO2 metasurface. Here, the black TiO2 was implanted with H+ ions for 4 min. (D) Top row SEM images of the black TiO2 metasurface after immersing it in AgNO3 solutions for (i) 0 s, (ii) 20 s, (iii) 40 s, and (iv) 60 s. Scale bars, 3 μm (i) and 5 μm (ii, iii, and iv). (E) Function of mean particle sizes with different illuminating times of the black TiO2 metasurface (red square line), the black TiO2 film (blue triangle line), and the conventional TiO2 metasurface (green dot line).

  • Fig. 5 TiO2 metasurface–based narrow-band absorber.

    (A) Reflection spectra of the TiO2 metasurface with l = 400 nm before (solid line) and after (dashed line) 1-min H+ ion implantation. The inset shows the top-view SEM image. Scale bar, 200 nm. (B) Enhancement factor (solid line) of light and the sizes (dots) of Ag nanoparticles as a function of wavelength.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/11/eaax0939/DC1

    Supplementary Text

    Section S1. The deposition and transition of TiO2 film

    Section S2. Fabrication process and characterization of the nanostructures

    Section S3. Numerical calculation and the Mie resonances in TiO2 metasurfaces

    Section S4. Characterization of TiO2 metasurfaces

    Section S5. Dynamic image in TiO2 metasurfaces

    Section S6. The photoreduction with TiO2 metasurfaces

    Fig. S1. The deposition and transition of TiO2 film.

    Fig. S2. Fabrication process and characterization of the nanostructures.

    Fig. S3. Numerical calculation and the Mie resonances in TiO2 metasurfaces.

    Fig. S4. The numerical simulation of Mie resonance.

    Fig. S5. The numerical simulation of the TiO2 metasurface before and after H+ implantation.

    Fig. S6. Optical measurement of TiO2 metasurfaces.

    Fig. S7. The color and reflection spectrum of TiO2 metasurfaces.

    Fig. S8. The SEM image of “COLOR” pattern without guide lines.

    Fig. S9. Setup for photoreduction and the characterization of the TiO2 metasurface in AgNO3 solution.

    Fig. S10. The contrast experiment of Ag photoreduction and characterization of the generated Ag nanoparticle.

    Fig. S11. Characterization of particle sizes of Ag photoreduction on TiO2 metasurfaces.

  • Supplementary Materials

    This PDF file includes:

    • Supplementary Text
    • Section S1. The deposition and transition of TiO2 film
    • Section S2. Fabrication process and characterization of the nanostructures
    • Section S3. Numerical calculation and the Mie resonances in TiO2 metasurfaces
    • Section S4. Characterization of TiO2 metasurfaces
    • Section S5. Dynamic image in TiO2 metasurfaces
    • Section S6. The photoreduction with TiO2 metasurfaces
    • Fig. S1. The deposition and transition of TiO2 film.
    • Fig. S2. Fabrication process and characterization of the nanostructures.
    • Fig. S3. Numerical calculation and the Mie resonances in TiO2 metasurfaces.
    • Fig. S4. The numerical simulation of Mie resonance.
    • Fig. S5. The numerical simulation of the TiO2 metasurface before and after H+ implantation.
    • Fig. S6. Optical measurement of TiO2 metasurfaces.
    • Fig. S7. The color and reflection spectrum of TiO2 metasurfaces.
    • Fig. S8. The SEM image of “COLOR” pattern without guide lines.
    • Fig. S9. Setup for photoreduction and the characterization of the TiO2 metasurface in AgNO3 solution.
    • Fig. S10. The contrast experiment of Ag photoreduction and characterization of the generated Ag nanoparticle.
    • Fig. S11. Characterization of particle sizes of Ag photoreduction on TiO2 metasurfaces.

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