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A neoteric approach to achieve CaF2:Eu2+/3+ one-dimensional nanostructures with direct white light emission and color-tuned photoluminescence

Yuebo Li,Haina Qi,Yunrui Xie,Liu Yang,Wensheng Yu,Qianli Ma,Xiangting Dong,Dan Li,Guixia Liu,Jinxian Wang

CaF 2 :Eu 2+/3+ one-dimensional nanostructures including nanofibers , hollow nanofibers and nanobelts are respectively constructed via a newly-proposed technique of high-efficient combination of electrospinning with bi-crucible fluorinating technique. The diameters of CaF 2 :Eu 2+/3+ nanofibers and hollow nanofibers are respectively 328 ± 2 nm and 290 ± 5 nm, and the width and thickness of nanobelts are 1.07 ± 0.013 μm and 150 nm, respectively. Under the excitation of 276-nm or 320-nm ultraviolet light, CaF 2 :Eu 2+/3+ nanostructures exhibit characteristic emission peaks at 385 nm (purple) and 615 nm (red) assigned to 4f 6 5 d 1 (t 2g )→ 8 S 7/2 energy levels transition of Eu 2+ ions and 5 D 0 → 7 F 2 energy levels transitions of Eu 3+ ions, respectively. XPS data further confirm the coexistence and proportion of Eu 2+ and Eu 3+ in the samples. CaF 2 :9%Eu 2+/3+ nanofibers possess the highest luminescent intensity. White-emitting and color-tunable photoluminescence performance of CaF 2 :Eu 2+/3+ nanostructures are realized by regulating the proportion of Eu 2+ to Eu 3+ ions, and luminescence mechanism is also proposed. Further, it is satisfactorily found that the proportion of Eu 2+ to Eu 3+ ions can be modulated by adjusting the Eu-doped concentration and calcination temperature. The detailed formation mechanisms of CaF 2 :Eu 2+/3+ one-dimensional nanostructures are advanced, and the neoteric fabrication technique is successfully established. This design conception and construction strategy can provide some guidance for fabricating other one-dimensional nanostructures.