Synthesis and optical properties of transparent β-NaYF₄:Yb, Tm/PMMA nanocomposites

The hexagonal β-NaYF₄:Yb, Tm particles and core-shell structure β-NaYF₄:Yb, Tm@β-NaYF₄:Yb particles were prepared by solvothermal method. The as-prepared particles were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and photoluminescence (PL) spectra. With the increasing of Yb³⁺ concentration, the luminus intensity of β-NaYF₄:Yb, Tm particle first increases, then decreases. When the mole fraction of Yb³⁺ is 30%, the intensities of 474, 645 nm reach the maximum, and when the mole fraction of Yb³⁺ is 50%, the intensities of 450, 692 nm reach the maximum. Then β-NaYF₄:30%Yb, Tm particls were coated by β-NaYF₄:Yb layer. When the mole fraction of Yb³⁺ in shell layer is 10%, the luminus intensity of β-NaYF₄:Yb, Tm@β-NaYF₄:Yb particle is the maximum. The luminus intensities of all the samples increase after heat treatment, and the blue luminus intensity decreases and red luminus intensity increases with the increasing of ambient temperature. The transparent composite materials of β-NaYF₄:Yb, Tm and PMMA were synthesized by in situ polymerization, and showed good luminescence property.