Synthesis, characterization and photoluminescent properties of rare-earth hydroxides and oxides nanorods by hydrothermal route

The stable and crystalline pure phase Ln(OH)3 (Ln=La, Nd, Sm, Eu, Gd, Tb, and Dy) nanorods are synthesized by a facile hydrothermal method using the simple chemical materials (rare-earth chloride hexahydrate LnCl3⋅6H2O and NH3⋅H2O) and polymer polyvinypyrrolidone (PVP). The as-prepared Ln(OH)3 nanorods can be successfully converted to Ln2O3 nanorods via calcination under appropriate conditions. X-ray diffraction (XRD) spectra, Fourier transformed infrared (FTIR) spectrum, scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-Resolution TEM (HRTEM), and Raman spectroscopy were used to examine the morphologies and microstructures to find out the cause. The analyzed results indicate that the obtained nanorods are rare-earth hydroxides and oxides with 1D nanostructures. The formation mechanism of the Ln(OH)3 and Ln2O3 nanorods was investigated. Optical properties of the Ln(OH)3 and Ln2O3 nanorods were determined by photoluminescence (PL). Ln(OH)3 and Ln2O3 nanorods exhibit a strong blue emission with the strongest narrow bands at about 469 nm corresponding to the intra-4f transitions 5D2→7F6, which have potential applications in fluorescent devices.