Min Pang,Xuesong Zhai,Jing Feng,Shuyan Song,Ruiping Deng,Zhuo Wang,Shuang Yao,Xin Ge,Hongjie Zhang
Water-soluble hexagonal NaScF4:Yb/Er nanocrystals have been directly synthesized via a facile one-step hydrothermal route. The as-prepared nanocrystals were monodisperse and could form stable colloidal solutions in polar solvents, such as water and ethanol. The novel NaScF4:Yb/Er nanocrystals exhibited intrinsic intense red upconversion emission, in contrast to other lanthanide-doped fluoride nanocrystals. Remarkably, the upconversion emission intensity was enhanced ∼6.8 times through the coating of an active-shell (containing Yb3+) surrounding the NaScF4:Yb/Er core nanocrystals, owing to surface passivation effect and efficient energy transfer from Yb3+ ions in both the core and the shell to Er3+ ions. These water-soluble hexagonal NaScF4:Yb/Er nanocrystals with intense red emission are ideal for a variety of in vitro and in vivo biological imaging applications.
Water-soluble hexagonal NaScF 4 :Yb/Er upconversion microcrystals (UCMCs) were synthesized using the hydrothermal method . The upconversion photoluminescence properties of NaScF 4 :xYb/2%Er microcrystals (x = 4–20%) were characterized under a 980-nm-wavelength laser excitation. The dependence of red/green (R/G) ratio on the concentration of Yb 3+ ions was investigated. The local environments of dopant ions (Yb 3+ , Er 3+ ) in NaScF 4 were studied using multiple solid-state nuclear magnetic resonance (NMR) techniques. The 19 F single pulse and 19 F{ 23 Na} and 19 F{ 45 Sc} rotational echo double resonance (REDOR) techniques proved that the dopant rare-earth ions (Yb 3+ , Er 3+ ) preferred to substitute Na + rather than Sc 3+ ions. Such solid-state NMR techniques provide a novel approach to study new phosphors.
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