Synthesis of rare earth (Pr, Nd, Sm, Eu and Gd) hydroxide and oxide nanorods (nanobundles) by a widely applicable precipitation route

Rare earth hydroxide and oxide nanorods (nanobundles) have been synthesized without the addition of any templates/surfactants by a simple precipitation method under ambient temperature and pressure. The products are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), field-emission scanning electron microscopy (FESEM), thermogravimetry (TG) and N2 adsorption/desorption. It is demonstrated that the rare earth hydroxide nanorods (nanobundles) have the diameter of 10–150 nm and the length of 30–600 nm. The corresponding oxides can be obtained by calcination, which preserved the nanorod (nanobundle) morphologies though a small shrinkage in sizes is observed. The influences of the aging time and precipitation agent on the formation of nanorods (nanobundles) are investigated. Accordingly the crystallization mechanism is proposed. The nucleation and growth of the hydroxide nanorods may occur in the precipitation process at relatively low (room) temperature and normal pressure without a long-time and high-temperature (pressure) hydrothermal treatment. The photoluminescence (PL) analysis is used to investigate the optical properties of the Eu2O3 nanobundles and a broadened luminescent spectrum is observed. The precipitation method is simple, highly reproducible, inexpensive, and widely applicable for the large-scale industrial production.

Research highlights▶ Rare earth hydroxide nanorods (nanobundles) were prepared by a precipitation method. ▶ Any templates or surfactants were not added. ▶ The nucleation and growth of nanorods occurred without a hydrothermal treatment. ▶ The morphology can be controlled by the aging time and precipitation agents. ▶ The 5D0–7F2 transition of Eu2O3 nanobundles decreased greatly compared with the bulk.