Research ArticleOPTICS

Scalable electrochromic nanopixels using plasmonics

See allHide authors and affiliations

Science Advances  10 May 2019:
Vol. 5, no. 5, eaaw2205
DOI: 10.1126/sciadv.aaw2205
  • Fig. 1 eNPoM nanopixel.

    (A) Schematic of an eNPoM, which changes color as a function of redox state of the thin (0 to 20 nm) PANI shell surrounding each Au NP on Au mirror substrate. Right: Redox reaction of PANI in the gap (PANI0, fully reduced; PANI1+, half oxidized; PANI2+, fully oxidized). (B) Optical near-field enhancement of the eNPoM for reduced state of PANI shell (PANI0) showing hot spot in gap and (C) its corresponding optical scattering (solid lines) and absorption spectra (dashed lines) for different redox states of the PANI shell (red to green: PANI0 to PANI2+), from numerical simulations (see Materials and Methods). (D) Experimental dark-field (DF) scattering images of a single eNPoM nanopixel for different redox states of the PANI shell (left to right: PANI0 to PANI2+).

  • Fig. 2 Electrically driven optical switching of single eNPoMs.

    (A) Cyclic voltammetry (CV) of eNPoMs, with current calibrated per eNPoM (0, PANI0; 1+, PANI1+; 2+, PANI2+; dashed background curve highlights redox peaks). (B) DF scattering spectra of single eNPoM versus voltage applied as in (A) (c0, PANI0; c2+, PANI2+). Inset shows SEM image of a representative eNPoM (80-nm Au NP coated with 20-nm PANI shell on Au substrate). (C) Time scan of normalized DF scattering spectra from a single eNPoM for five cycles of ramped voltage −0.2 ↔0.6 V with a scan rate of 50 mV/s. (D) Reversible switching of coupled plasmon mode versus applied voltage.

  • Fig. 3 eNPoMs with varying gaps.

    (A) Top: SEM images of Au NPs coated with different thicknesses of surrounding PANI shell layer (11, 13, 18, and 20 nm from left to right). Bottom: Corresponding DF images (top, PANI0; bottom, PANI2+). (B) CV curves of four different eNPoMs composed of 11-nm (red), 13-nm (orange), 18-nm (green), and 20-nm PANI shells (blue) versus applied voltage (from left to right). (C) Dynamic response in DF scattering of each NPoM nanopixel versus gap size. (D) Optical tuning (red, c0; green, c2+) and (E) corresponding intensity switching of eNPoMs as a function of PANI thickness (gap size) from theory (dashed lines) and experiment (circles and solid lines). (F) Associated color gamut plots (CIE 1931 chromaticity).

  • Fig. 4 Electrical and optical switching dynamics of eNPoM nanopixels.

    (A) Schematic of electron transfer from PANI to Au mirror through the gap. (B) Charge flow per nanoparticle in the gap of each eNPoM versus applied potential. (C) Optical dynamics of coupled plasmon mode versus number of electrons transferred at the gap. (D) Square-wave modulation of the applied potential at 1 Hz (top) and associated normalized scattering intensity (bottom) of single eNPoM at wavelength of c0 peak, showing dynamics for reduction (143 ms) and oxidation (32 ms). (E) Reversible optical switching of an eNPoM under square-wave modulation at 1, 10, and 20 Hz. (F) Switching contrast of eNPoM versus applied modulation frequency.

  • Fig. 5 Scalable color generation performance of eNPoM metasurfaces.

    (A) Schematic of eNPoM metasurface integrated into electrochemical cell. Right inset shows optical near-field enhancement of two eNPoMs built from 60-nm Au NPs, separated by mean distance gFF = 90 nm (given 20% fill fraction), showing no optical near-field coupling between the eNPoMs. (B) Corresponding simulated spectra. (C) Experimental scattering spectra of the eNPoM metasurfaces versus voltage applied from −0.3 ↔ 0.8 V. (D) DF images and (E) color gamut (CIE 1931 chromaticity) of the eNPoM metasurfaces built from 20-, 40-, and 60-nm-diameter Au NPs during PANI redox. (F) Color dynamics of eNPoM metasurface from (C) under ambient light before and after 3 months. Photo credit: J. Peng and H.-H. Jeong, University of Cambridge.

  • Fig. 6 Optical dynamics of electrochromic plasmonic nanoparticles.

    Switching times of various electrochromic plasmonic nanomaterials versus their associated (A) optical dynamic ranges and (B) pixel areas: eNPoMs (red circle), Au nanospheres (NS) coated with PANI (yellow circle), Au rods coated with PANI (yellow square), Au bipyramids (BP) coated with PANI (yellow bipyramid) (15), Au discs coated with PANI (yellow triangle) (16), Au domes coated with Ag (gray hexagon) (7), and Au dimers coated with Ag (gray circle) (13). Green box indicates needs for commercial displays, matching what can be achieved with eNPoMs (red).

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/5/eaaw2205/DC1

    Fig. S1. FDTD simulations of Au NPs and eNPoMs.

    Fig. S2. Electrochemical cell.

    Fig. S3. PANI coating on Au NPs with thickness control.

    Fig. S4. FDTD numerical simulation of eNPoM for different redox states in the gap.

    Fig. S5. Electrochemical analysis of eNPoMs.

    Fig. S6. Reversible optical switching of eNPoMs.

    Fig. S7. eNPoM metasurfaces.

    Fig. S8. Angular dependence of eNPoM metasurfaces.

    Fig. S9. Power density of various displays.

    Table S1. Comparison of electrochromic plasmonic reflective devices.

    Movie S1. Matrix (6 × 6) of the DF scattering images of the eNPoMs as a function of time during CV cycle in the range of −0.2 to 0.6 V (versus Ag/AgCl) with a scan rate of 50 mV/s.

    Movie S2. DF scattering images of four different particles (in row) of four different eNPoMs composed of 11-, 13-, 18-, and 20-nm PANI thicknesses as a function of time during CV cycle in the range of −0.2 to 0.6 V (versus Ag/AgCl) with a scan rate of 50 mV/s.

    Movie S3. DF scattering images of the eNPoM metasurfaces as a function of time during CV cycle in the range of −0.2 to 0.6 V (versus Ag/AgCl) with a scan rate of 50 mV/s.

  • Supplementary Materials

    The PDF file includes:

    • Fig. S1. FDTD simulations of Au NPs and eNPoMs.
    • Fig. S2. Electrochemical cell.
    • Fig. S3. PANI coating on Au NPs with thickness control.
    • Fig. S4. FDTD numerical simulation of eNPoM for different redox states in the gap.
    • Fig. S5. Electrochemical analysis of eNPoMs.
    • Fig. S6. Reversible optical switching of eNPoMs.
    • Fig. S7. eNPoM metasurfaces.
    • Fig. S8. Angular dependence of eNPoM metasurfaces.
    • Fig. S9. Power density of various displays.
    • Table S1. Comparison of electrochromic plasmonic reflective devices.

    Download PDF

    Other Supplementary Material for this manuscript includes the following:

    • Movie S1 (.mov format). Matrix (6 × 6) of the DF scattering images of the eNPoMs as a function of time during CV cycle in the range of −0.2 to 0.6 V (versus Ag/AgCl) with a scan rate of 50 mV/s.
    • Movie S2 (.mov format). DF scattering images of four different particles (in row) of four different eNPoMs composed of 11-, 13-, 18-, and 20-nm PANI thicknesses as a function of time during CV cycle in the range of −0.2 to 0.6 V (versus Ag/AgCl) with a scan rate of 50 mV/s.
    • Movie S3 (.mov format). DF scattering images of the eNPoM metasurfaces as a function of time during CV cycle in the range of −0.2 to 0.6 V (versus Ag/AgCl) with a scan rate of 50 mV/s.

    Files in this Data Supplement:

Navigate This Article