OH^- ions-controlled synthesis and upconversion luminescence properties of NaYF₄:Yb³⁺,Er³⁺ nanocrystals via oleic acid-assisted hydrothermal process

【摘要】 Yb³⁺ and Er³⁺ ions co-doped NaYF₄ nanocrystals were synthesized with different amounts of NaOH via oleic acid（OA）-assisted hydrothermal process. X-ray diffraction（XRD）, scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, Fourier transform infrared spectroscopy（FTIR）, and photoluminescence spectra were used to characterize the products. The result indicated that the introduction of Na OH into the initial reaction solution effectively promoted the cubic（α-） to hexagonal（β-） phase transition of NaYF₄:Yb³⁺,Er³⁺ nanocrystals, while excessive amount of Na OH favored the formation of α-NaYF₄:Yb³⁺,Er³⁺ nanocrystals. Besides, with the increase of Na OH amount, the morphologies of β-NaYF₄:Yb³⁺,Er³⁺ nanocrystals varied from irregular nanobranch to uniform nanorod. Further investigation revealed that the addition of Na OH could facilitate the deprotonation of OA, leading to the formation of oleate（OA–）, and meanwhile increased the concentration of OH– ions, inducing consequently the phase transition and morphology evolution of NaYF₄:Yb³⁺,Er³⁺ nanocrystals. Moreover, the upconversion luminescence properties of NaYF₄:Yb³⁺,Er³⁺ nanocrystals were systematically investigated. It was found that the upconversion emissions not only depended on the phase and morphology but also were influenced by the surface groups.更多还原

【Abstract】 Yb³⁺ and Er³⁺ ions co-doped NaYF₄ nanocrystals were synthesized with different amounts of NaOH via oleic acid（OA）-assisted hydrothermal process. X-ray diffraction（XRD）, scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, Fourier transform infrared spectroscopy（FTIR）, and photoluminescence spectra were used to characterize the products. The result indicated that the introduction of Na OH into the initial reaction solution effectively promoted the cubic（α-） to hexagonal（β-） phase transition of NaYF₄:Yb³⁺,Er³⁺ nanocrystals, while excessive amount of Na OH favored the formation of α-NaYF₄:Yb³⁺,Er³⁺ nanocrystals. Besides, with the increase of Na OH amount, the morphologies of β-NaYF₄:Yb³⁺,Er³⁺ nanocrystals varied from irregular nanobranch to uniform nanorod. Further investigation revealed that the addition of Na OH could facilitate the deprotonation of OA, leading to the formation of oleate（OA–）, and meanwhile increased the concentration of OH– ions, inducing consequently the phase transition and morphology evolution of NaYF₄:Yb³⁺,Er³⁺ nanocrystals. Moreover, the upconversion luminescence properties of NaYF₄:Yb³⁺,Er³⁺ nanocrystals were systematically investigated. It was found that the upconversion emissions not only depended on the phase and morphology but also were influenced by the surface groups.更多还原