(Color online) TEM images and XRD patterns of 20% Yb3+/5% Er3+ doped hexagonal NaYF4 nanoplates (a), nanorods (b) and XRD patterns of standard β-phase NaYF4 (28-1192) (c).
(Color online) Emission spectra of rod-shaped (a) and plate-shaped (b) NaYF4:20% Yb3+/5% Er3+ NCs under 977 nm excitation. The spectra are multiplied by the factors shown on the figure.
(Color online) Simplified energy scheme of Yb3+ and Er3+ ions. The curved arrows on the left stand for energy transfer processes.
(Color online) Emission spectra of NaYF4: Er3+/Yb3+ nanorods. The relevant excited wavelengths are 355 nm (a), 532 nm (b) and 977 nm (c), respectively. The inset is the excitation spectra monitored at 544 nm for nanorod (d) and nanoplate (e).
(Color online) Emission spectra of doped NaYF4 UPNPs under 532 nm excitation. (a) NaYF4:Eu3+ nanorod; (b) NaYF4:Eu3+ nanoplate; (c) NaYF4:Er3+/Yb3+ nanorod; (d) NaYF4:Er3+/Yb3+ nanoplate. The inset is the lifetimes monitored at 544 nm for NaYF4:Er3+/Yb3+ nanorods (e) and nanoplates (f).
(Color online) FTIR spectra of the rod-shaped (a) and plate-shaped (b) NaYF4:Er3+/Yb3+ UCNPs.
(Color online) Schematic structures, crystal planes, TEM images of different shaped UCNPs. (a) NaYF4:Er3+/Yb3+ nanorod; (b) NaYF4:Er3+/Yb3+ nanoplate.
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