Fig. 1. (a) Construction scheme of the preparation process of GVA@SiO2@NaYF4:Yb3+/Er3+; (b) the typical SEM images of the large-scale and corresponding small-scale GVA; (c) the SEM images of the GVA@SiO2 (8 nm), and the cross-sectional view of the spin-coated NaYF4:Yb3+/Er3+ nanocrystals; (d) the ultraviolet-visible absorption spectrum of GNRs; TEM images of (e) NaYF4:20%Yb3+/2%Er3+ and (f) NaYF4: 40%Yb3+/2%Er3+ nanocrystals; (g) XRD patterns of NaYF4:20%Yb3+/2%Er3+ and NaYF4: 40%Yb3+/2%Er3+ nanocrystals.
Fig. 2. Schematic explanation of confocal microscopy setup.
Fig. 3. (a) and (b) Upconversion emission spectra and enhancement factor of different systems under 980 nm excitation; (c) and (d) the peak area of the green and red emission intensity and corresponding R/G ratio of the NaYF4:20%Yb3+/2%Er3+ with wafer and different thicknesses of isolation layer about from 0 to 8 nm (RE1: NaYF4: 20%Yb3+/2%Er3+; M-RE1, M-RE14 and M-RE18: GVA@SiO2 (0, 4, 8 nm)@NaYF4: 20%Yb3+/2%Er3+).
Fig. 4. (a) and (b) Upconversion emission spectra and enhancement factor of different systems under 980 nm excitation; (c) and (d) the peak area of the green and red emission intensity and corresponding R/G ratio of the NaYF4:40%Yb3+/2%Er3+ with wafer and different thicknesses of isolation layer about from 0 to 8 nm (RE2: NaYF4:40%Yb3+/2%Er3+; M-RE2, M-RE24, and M-RE28: GVA@SiO2 (0, 4, 8 nm)@NaYF4:40%Yb3+/2%Er3+).
Fig. 5. Energy level transition diagram and enhancement mechanism of LSPR.
Fig. 6. (a) Upconversion emission spectra of GVA@SiO2 (8 nm)@NaYF4:40%Yb3+/2%Er3+ nanocrystals; (b) and (c) are graphs corresponding to the emission intensity and the red-green ratio as a function of the 980 nm laser excitation power from 40 mW to 160 mW.
Fig. 7. Life decay of green (4S3/2 level) upconversion emission of NaYF4:20%Yb3+/2%Er3+ nanocrystal with the thickness of the isolation layer under 980 nm excitation.
Fig. 8. Local electromagnetic field distribution of the smallest unit of the GVA@SiO2 system is simulated under 980 nm excitation: (a) The local electromagnetic field distribution map of the x-y plane; (b) the GVA@SiO2 (2 nm) of x-z cross-section local electromagnetic field distribution diagram was illustrated; (c) the intensity of the localized electromagnetic field hot spot produced by the LSPR with the SiO2 thickness changed.
Sample | Lifetime/μs (540 nm) | a: NaYF4:20%Yb3+/2%Er3+ | 361.945 ± 1.681 | b: AuNRs Array/NaYF4:20%Yb3+/2%Er3+ | 358.005 ± 1.679 | c: AuNRs array/4 nm SiO2/NaYF4:20%Yb3+/2%Er3+ | 342.060 ± 1.571 | d: AuNRs array/8 nm SiO2/NaYF4:20%Yb3+/2%Er3+ | 212.075 ± 0.892 |
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Table 1. Luminescence lifetimes of 4S3/2 energy level (540 nm) in GVA@SiO2@NaYF4: 20%Yb3+/2%Er3+ composite system under 980 nm pulse laser excitation.
980 nm脉冲激发光激发下GVA@SiO2@NaYF4:20%Yb3+/2%Er3+复合体系中Er3+离子的4S3/2能级辐射寿命