Abstract
NaYF4:Ln3+, due to its outstanding upconversion characteristics, has become one of the most important luminescent nanomaterials in biological imaging, optical information storage, and anticounterfeiting applications. However, the large specific surface area of NaYF4:Ln3+ nanoparticles generally leads to serious nonradiative transitions, which may greatly hinder the discovery of new optical functionality with promising applications. In this paper, we report that monodispersed nanoscale NaYF4:Ln3+, unexpectedly, can also be an excellent persistent luminescent (PersL) material. The NaYF4:Ln3+ nanoparticles with surface-passivated core–shell structures exhibit intense X-ray-charged PersL and narrow-band emissions tunable from 480 to 1060 nm. A mechanism for PersL in NaYF4:Ln3+ is proposed by means of thermoluminescence measurements and host-referred binding energy (HRBE) scheme, which suggests that some lanthanide ions (such as Tb) may also act as effective electron traps to achieve intense PersL. The uniform and spherical NaYF4:Ln3+ nanoparticles are dispersible in solvents, thus enabling many applications that are not accessible for traditional PersL phosphors. A new 3-dimensional (2 dimensions of planar space and 1 dimension of wavelength) optical information-storage application is demonstrated by inkjet-printing multicolor PersL nanoparticles. The multicolor persistent luminescence, as an emerging and promising emissive mode in NaYF4:Ln3+, will provide great opportunities for nanomaterials to be applied to a wider range of fields.
Highlights
In the past decades, lanthanide-activated NaYF4(NaYF4:Ln3+) has become one of the best-known luminescent nanomaterials[1–3]
persistent luminescent (PersL) in NaYF4:Ln3+ and the core–shell structure A surface-passivated core–shell structure was adopted for the synthesis of nanoparticles (i.e., NaYF4: Ln3+@NaYF4, as schematically illustrated in Fig. 1a), which would impact a positive effect on the PersL performance, as reported in the upconversion studies[9]
The PersL intensity was linearly increased with the increase of irradiation time up to 4500 s (Fig. S3b), which indicated that the nanoparticles possessed a high storage capacity of X-rayinduced charge carriers in traps and the used X-ray dose rate was quite small to reach saturation charging
Summary
(NaYF4:Ln3+) has become one of the best-known luminescent nanomaterials[1–3]. NaYF4:Ln3+ has found a wide range of applications in in vivo/in vitro bioimaging[7–13], biological therapy[14–17], optical sensors18–20, 3dimensional (3D) optical information storage[21,22], and volumetric 3D displays[23]. Over the past twenty years, the efforts to explore more functionalities in NaYF4:Ln3+ nanoparticles have never stopped. The large specific surface area of nanoparticles causes emission quenching, which greatly hinders the discovery and application of new functionalities. Persistent luminescence (PersL, known as afterglow) is a slow photon emission resulting from the controlled release of charge carriers from traps in solid-state luminescent materials[24–26]. PersL materials with unique delayed emission have received much attention and exhibit great promise in night-vision security[27–30], Zhuang et al Light: Science & Applications (2021)10:132
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