Yini Mao,Pengfei Xian,Li Jiang,Shanshan Hu,Jianfeng Tang,Jun Yang
NaScF4:Yb3+/Er3+ crystals were successfully hydrothermally synthesized using distilled water as a single solvent. The crystal phase and morphology were characterized by XRD and SEM. Compared with organic solvents such as ethanol, ethylene glycol and ether, the molar ratio of Na/F/Sc plays an important role in the synthesis of NaScF4 crystals. Morphological control was achieved by changing the types of additives, and the relationship between morphology and luminescence properties was explored. The NaScF4:Yb3+/Er3+ phosphors exhibit strong green and red UC emissions under the excitation of 980 nm NIR. Optimal concentrations of Yb3+ and Er3+ for up-conversion luminescence performance were identified as 10% and 2%, respectively. Without any subsequent heat treatment process, the obtained NaScF4:10%Yb3+/2%Er3+ showed good temperature sensitivity. The temperature sensing ability was investigated by employing the dependence of the fluorescence intensity ratio (FIR) of the two thermal coupling energy levels of Er3+ (2H11/2 → 4I15/2 and 4S3/2 → 4I15/2) on temperature; the maximum sensitivity SA/SR was 0.00256 K−1/0.00317 K−1 at 548 K, and it increased to 0.00328 K−1/0.00413 K−1 after adding EDTA. In addition, an evaluation of temperature uncertainty during temperature measurement was performed, and was found to be 0.073 K and 0.095 K in the presence and absence of EDTA, respectively. Compared with some other reported materials, the obtained material shows a relatively superior temperature sensitivity, which provides new ideas for the improvement of temperature-sensitive materials.
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.
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.
Jingjing Cao,Li Yuan,Shanshan Hu,Jianfeng Tang,Xianju Zhou,Jun Yang
Monodisperse ScF3 and NaScF4 nano-/micro-crystals were prepared by a simple solvothermal method. There were many important factors including the molar ratio of Na/F/(Sc + Ln) and Ln3+ doping to control the synthesis of the products. A phase transformation from monoclinic ScF3 to hexagonal NaScF4 was observed with different molar ratios of Na/F/Sc. Herein, the products doped with 1% Ln3+ (La–Lu, except Pm) demonstrated abundant phases, morphologies and sizes. Moreover, the products with different Lu3+ doping concentrations from 1% to 60% were prepared. The results revealed that different kinds of 1% Ln3+ (La–Lu, except Pm) and diverse concentrations of Lu3+ can modify the phase, morphology and size of the prepared products. A possible formation mechanism for the products with diverse morphologies is proposed. In addition, Ln3+-doped ScF3 or NaScF4 nano-/micro-crystals presented characteristic up/down-conversion fluorescence spectra.
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