Synthesis and spectral characterization of EuPO4 and LaPO4:Eu nanorods.

Monoclinic monazite-type EuPO4 and LaPO4:Eu nanorods were synthesized by a microemulsion-assisted solvothermal method. Their morphologies, structures, and fluorescent properties were characterized by SEM, XRD, and photoluminescence (PL) modern analytic means, respectively. The aspect ratios of EuPO4 and LaPO4:Eu nanorods have a decreasing tendency with increasing carbon chain length of assisted surfactants. When the assisted surfactant was n-butyl alcohol, the EuPO4 exhibited nanorod morphology with diameters from 20 to 30 nm and lengths from 100 to 150 nm. When the assisted surfactant was n-pentanol, the EuPO4 nanorods had lengths between 200 and 300 nm and a diameter range similar to that of the n-butyl alcohol nanorods. When the assisted surfactant was n-hexanol and n-octyl alcohol, only elliptical EuPO4 products were obtained. The LaPO4:Eu nanorods synthesized in the presence of different assisted-surfactants exhibited elliptical morphologies with diameters of 40-60 nm and lengths of 70-110 nm. The LaPO4:Eu and EuPO4 nanorods showed a orange prominent emission peak from magnetic-dipole transition 5D0 --> F1 (593 nm) of Eu3+ ions whose sites in the EuPO4 and LaPO4:Eu nanorods have C1 symmetry. Compared with bulk LaPO4:Eu, the fine structure of the Eu-O charge transfer band has very small red shift resulting from the slight increase of the length of Eu-O bond due to nanoscale size effect.