Rare-Earth-Ion-Doped Hexagonal-Phase NaYF4 Nanowires: Controlled Synthesis and Luminescent Properties

摘要

Rare-earth-ion-doped hexagonal-phase NaYF4 nanowires were hydrothermally synthesized at the cooperative effect of sodium citrate with AOT on a large scale. As-synthesized nanowires have a uniform size with several micrometers in length and ca. 100 nm in diameter. The XRD pattern of the products is notably different from the standard one of NaYF4 based on the comparison of relative diffraction peak intensities (hkO) to (hkl), indicating the preferred orientation. SAED and HRTEM show that hexagonal-phase NaYF4 nanowires grow along the [001] crystallographic direction. Organic addition agent, sodium citrate, and AOT have a remarkable influence on morphologies of the final products. According to XRD analysis and SEM observation of the products at different reaction time periods, the formation mechanism of hexagonal-phase NaYF4 nanowires was proposed. The photoluminescence properties of hexagonal-phase NaYF4:Ln~(3+) (Ln = Tb and Yb/Er) nanowires at different doping concentrations were investigated. The up-conversion mechanism of Yb~(3+)/Er~(3+)-codoped NaYF4 nanowires was also discussed briefly.