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Three-level spaser for next-generation luminescent nanoprobe

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Science Advances  17 Aug 2018:
Vol. 4, no. 8, eaat0292
DOI: 10.1126/sciadv.aat0292
  • Scheme 1 Conceptual diagram of a three-level spaser.
  • Fig. 1 Demonstration of a three-level spaser.

    Schematic structure (A), TEM (B), and FDTD-simulated electric field distribution (C) images of the Au@dye/SiO2 nanoprobe [yellow core and green layer in (A) denote the Au core and the outer dye-doped SiO2 layer, respectively]. (D) Plasmon resonance absorption (1), excitation (2), spontaneous emission (3), split spontaneous emission S1S0 (4) and T2S0 (5), and stimulated emission (6) curves of the nanoprobe. Inset in (D) is the observed stimulated emission spectrum of the nanoprobe. Emission lifetime of S1S0 (E) and T2S0 (F) by using the dye. a.u., arbitrary units; FWHM, full width at half maximum.

  • Fig. 2 Ultralow pump threshold of a three-level spaser.

    (A) Emission spectra of the as-prepared dsDs with the pump energy changing from 0.5 to 1.5 mJ cm−2. (B) The corresponding FWHM (blue line) and emission intensity (red line) vary with the pump energy. SE, spontaneous emission. (C) Emission spectra of the gain material without plasmon cavity under pump energy of 0.4 to 1.5 mJ cm−2. (D) Curves of emission intensity at 520 and 540 nm (left) and their ratio (right) with the changing of pump energy.

  • Fig. 3 Delayed spasing dynamics.

    (A) Time-resolved emission spectra of the as-prepared dsDs (temporal resolution, 1 μs). (B) Emission dynamics of gain medium itself (line 1) and dsDs (line 2) at 545 nm. BG, background. (C) Time-resolved emission spectra of gain material without plasmon cavity. (D) Decay curves of emission intensity at 520 and 540 nm, corresponding to delayed fluorescence (τ = 6.6 μs) and phosphorescence (τ = 14.6 μs).

  • Fig. 4 Electron transition dynamics.

    (A) Picosecond transient absorption spectra of the gain material without plasmon cavity. (B) Evolution of transient absorptive signature of S1Sn (470 nm, τ = 21.5 ps) and T2Tn (570 nm, τ = 25.3 ps) along with time, corresponding to a fast intersystem crossing. (C) Decay of transient absorption at 430 nm represents nonradiative relaxation of SiO2 (τ = 6.8 ps). The dip of about 490 to 530 nm could be attributed to the overlap of ground-state absorption and fluorescence emission. OD, optical density.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/4/8/eaat0292/DC1

    Supplementary Text

    Instruction of broadband time-resolved emission spectroscopy

    Fig. S1. Schematic diagram of broadband time-resolved emission spectroscopy system.

    Fig. S2. Molecular modeling of the dye.

    Fig. S3. Photoluminescent spectrum measurement.

    Fig. S4. Morphology characterization of the control samples.

    Fig. S5. Pump-dependent steady-state emission and time-resolved emission spectra of dye solution.

    Fig. S6. Electron transition dynamic spectrum of dye solution.

  • Supplementary Materials

    This PDF file includes:

    • Supplementary Text
    • Instruction of broadband time-resolved emission spectroscopy
    • Fig. S1. Schematic diagram of broadband time-resolved emission spectroscopy system.
    • Fig. S2. Molecular modeling of the dye.
    • Fig. S3. Photoluminescent spectrum measurement.
    • Fig. S4. Morphology characterization of the control samples.
    • Fig. S5. Pump-dependent steady-state emission and time-resolved emission spectra of dye solution.
    • Fig. S6. Electron transition dynamic spectrum of dye solution.

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