Facile synthesis, growth mechanism and luminescence properties of uniform La(OH)(3) : Ho3+/Yb3+ and La2O3 : Ho3+/Yb3+ nanorods

One-dimensional (1D) La2O3 and La2O3 : Ln(3+) (Ln = Ho/Yb) nanorods have been successfully synthesized at a mild condition via a facile homogenous precipitation method followed a heat treatment of their corresponding hydroxides. It can be found that the type of alkali and dosage of urea play crucial roles in the formation of uniform lanthanum hydroxide nanorods. The lanthanum hydroxide nanorods are morphology-formative intermediate for the formation of lanthanum oxides nanorods. The possible formation processes of 1-D lanthanum hydroxide and oxide nanorods were investigated. Under ultraviolet light and low-voltage electron beam excitation, the as-prepared Ho3+-doped La2O3 nanorods show a strong green emission corresponding to S-5(2) -> I-5(8) transition of Ho3+ ions, which possesses sharper transition lines in the green region and higher color purity than that of commercial ZnO : Zn phosphor. At the same time, La2O3 : Ho3+ nanorods have higher luminescence intensity than its bulk samples under the same excitation condition. Furthermore, green and red up-conversion emissions originating from two-photon ESA and ET are also observed from the La2O3 : Yb3+, Ho3+ nanorod samples.