Synthesis, Structural Characterization and Up-Conversion Luminescence Properties of NaYF 4 :Er 3+ ,Yb 3+ @MOFs Nanocomposites

This paper describes a facile synthesis of NaYF 4 :Er 3+ ,Yb 3+ nanoparticles embraced in metal–organic frameworks (MOFs), known as NaYF 4 :Er 3+ , Yb 3+ @MOFs core/shell nanostructures, by using iron(III) carboxylate (MIL-100) and zeolitic imidazolate frameworks (ZIF-8). Morphological, structural and optical characterization of these nanostructures were investigated by field emission-scanning electron microscopy, Fourier transform infrared spectroscopy, x-ray diffraction, and up-conversion luminescence measurements. Results showed that spherical-shaped NaYF 4 :Er 3+ ,Yb 3+ @MIL-100 nanocomposites with diameters of 150–250 nm, and rod-shaped NaYF 4 :Er 3+ ,Yb 3+ @ZIF-8 nanocomposites with lengths of 300–550 nm, were successfully synthesized. Under a 980-nm laser excitation at room temperature, the NaYF 4 :Er 3+ ,Yb 3+ @MOFs nanocomposites exhibited strong up-conversion luminescence with two emission bands in the green part of spectrum at 520 nm and 540 nm corresponding to the 2 H 11/2 → 4 I 15/2 and 4 S 3/2 → 4 I 15/2 transitions of Er 3+ ions, respectively, and a red emission band at 655 nm corresponding to the 4 F 9/2 → 4 I 15/2 transition of Er 3+ ions. The above properties of NaYF 4 :Er 3+ ,Yb 3+ @MOFs make them promising candidates for applications in biotechnology.