Sc3+共掺杂对单个NaGdF4∶Yb3+, Er3+微晶的上转换荧光调控

doi:10.3964/j.issn.1000-0593(2017)11-3347-07

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Abstract In a hydrothermal atmosphere with high temperature and long reaction time, a kind of special rare earth doped fluoride microcrystal was obtained with Sc³⁺ co-doping. The crystal phase and morphology of as-prepared samples were characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray detector (EDX) and element mapping. It is found that the Sc³⁺-free sample can be ascribed to the pure hexagonal NaGdF₄, and the Sc³⁺-doped samples are composed of hexagonal NaGdF₄- and monoclinic Na₃ScF₆-based microcrystals. With increasing of the doped concentration of Sc³⁺, the morphology of NaGdF₄-based microcrystal changes from lantern with cracked ends to octadecahedron with smooth surfaces, accomplished with a decreased size. It is worth mentioning that the concentration of Sc³⁺ that really entered into the host lattice is much less than the Sc³⁺ concentration in the precursor. Excited by 980 nm laser, the upconversion emission spectrum of single microcrystal was obtained by laser scanning confocal microscopy technology. For a single NaGdF₄∶Yb³⁺,Er³⁺ microcrystal, the significant upconversion fluorescence regulation was obtained by doping a few Sc³⁺ into the host lattice, and the relative intensity of the green upconversion emission (²H_11/2/⁴S_3/2→⁴I_15/2) to the red counterpart (⁴F_9/2→⁴I_15/2) increases gradually with the increasing of Sc³⁺ doped concentration. Combining with the suggested upconversion mechanisms, the influence of Sc³⁺ doped concentration on the rise time of upconverion fluorescence decay curve and the dependence of integrated intensity of upconverion emission band vs excitation power have been explored. It is found that the rise time of the upconversion fluorescence decay curve decreases gradually with the increase of the doped concentration of Sc³⁺, which confirms that the energy transfer rate (from Yb³⁺ to Er³⁺) obtains a significant increase by the introduction of Sc³⁺. It makes the population of ²H_11/2/⁴S_3/2 excited state easier than the ⁴F_9/2 counterpart, then induces the considerable upconversion fluorescence regulation. As the emission color of the NaGdF₄-based microcrystal is easy to adjust, it is excepted to show a great potential in the fields of fluorescence anti-counterfeiting, optical waveguide, and so on. The upconversion fluorescence regulation of single rare earth doped microcrystal induced by codoping with small radius ion can be applied to other luminous hosts.

Key words：Hydrothermal method; Sc³⁺ co-doping; NaGdF₄∶Yb³⁺,Er³⁺ microcrystal; Fluorescence regulation; Energy transfer

Received: 2016-08-04 Accepted: 2017-01-10

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https://www.gpxygpfx.com/EN/10.3964/j.issn.1000-0593(2017)11-3347-07 OR https://www.gpxygpfx.com/EN/Y2017/V37/I11/3347