La(OH)(3):Ln(3+) and La2O3:Ln(3+) (Ln = Yb/Er, Yb/Tm, Yb/Ho) Microrods: Synthesis and Up-conversion Luminescence Properties

One-dimensional La(OH)(3):Ln(3+) (Ln = Yb/Er, Yb/Tm, Yb/Ho) microrods have been successfully synthesized using molten composite-hydroxide (NaOH/KOH) as a solvent. La2O3:Ln(3+) nanostructures with retained striplike shape were achieved by a subsequent annealing process. The phase, structure, morphology, and fluorescent properties have been well investigated by various techniques. It is found that the reaction time plays a key role in confining the growth of the microrods. Both La(OH)(3):Ln(3+) and La2O3:Ln(3+) nanostructures have rodlike shapes with a typical width of 50-400 nm. The up-conversion (UC) photoluminescence (PL) properties of the samples have been studied in detail. Under 980 nm laser excitation, both La(OH)(3):Ln(3+) and La2O3:Ln(3+) microrods exhibit the characteristic emissions of Er3+, Tm3+, and Ho3+ and give green, blue, and blackish green emission colors, respectively. Additionally, the doping concentration of Yb3+ has been optimized by fixing the Er3+ concentration. It should be noted that the up-conversion emission of La2O3:Er3+ microrods can be significantly improved in comparison with that of their bulk counterpart under the same excitation conditions