Template-free synthesis, growth mechanism and photoluminescent properties of Ln(OH) 3 and Ln 2O 3 nanorods (Ln: lanthanide ion)

Abstract

Uniform and well-defined single-crystalline Ln(OH) 3 and La(OH) 3:Eu 3+ (Ln: lanthanide ion) nanorods were successfully synthesized by a large-scale and facile hydrothermal method only using Ln(NO 3) 3·6H 2O as lanthanide source and H 2O 2 as controller without any surfactant or template. The as-formed product via the hydrothermal process, La(OH) 3:Eu 3+, could transform to hexagonal La 2O 3:Eu 3+ with the same morphology by a postannealing process. The above mentioned samples were characterized by means of X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED) and photoluminescence (PL) spectra. By tuning the hydrothermal treatment time, a morphological evolution between the nanoparticles and nanorods was observed. Furthermore the growth mechanism and the morphological evolution of different shapes were investigated. Unlike traditional synthesis of Ln(OH) 3, H 2O 2 does not leave any impurity in the reaction system and makes the process very simple to obtain and separate the nanoparticles, nanomultipods and nanorods morphology. The La 2O 3:Eu 3+ nanorods exhibit a strong red emission corresponding to 5D 0 → 7F 2 transition (625 nm) of Eu 3+ under UV light excitation (282 nm), which have potential applications in fluorescent devices.