Intense blue photoluminescence of the Tm 3+/Yb 3+ co-doped single-crystalline hexagonal phase NaYF 4 nanorods

Abstract

In this paper, Tm 3+/Yb 3+ co-doped NaYF 4 single-crystalline nanorods were prepared via a rational hydrothermal method using oleic acid as a stabilizing agent. The microstructure analysis revealed that the as-prepared samples presented a pure hexagonal phase NaYF 4 structure with high quality rod-like morphology by means of X-ray diffraction (XRD) and transmission electron microscopy (TEM). Under 980 nm excitation, the intense blue and weaker red upconversion emissions of the NaYF 4: 1%Tm 3+/ x%Yb 3+ ( x = 2, 5, 10 and 15) samples centered at 450, 477, 649 and 690 nm were observed, which were attributed to the 1D 2 → 3F 4, 1G 4 → 3H 6, 1G 4 → 3F 4 and 3F 3 → 3H 6 transitions of Tm 3+, respectively. Moreover, the photograph of the 1%Tm 3+/10%Yb 3+ co-doped NaYF 4 nanorods exhibited a strong eye-visible blue emission. The upconversion luminescence mechanisms for the Tm 3+/Yb 3+ co-doped hexagonal phase NaYF 4 nanorods were analyzed. In addition, the effect of Yb 3+ ions concentrations on the photoluminescence properties of the Tm 3+/Yb 3+ co-doped hexagonal phase NaYF 4 nano-rods were investigated in detail.