Controllable synthesis and luminescent properties of LaVO4: Eu nanocrystals

Pure monoclinic and tetragonal LaVO4:Eu nanocrystals with various morphologies were successfully synthesized by a hydrothermal method in the presence of ethylenediaminetetraacetic acid [EDTA or H4L, where L4− = (CH2COO)2 N (CH2)2 N(CH2COO)24−]. It was found that tuning the pH of the growth solution was a crucial step for the synthesis of LaVO4:Eu nanocrystals with controllable crystal structure and morphology. When the pH value was lower than 2.5, urchin-like monoclinic LaVO4:Eu nanostructures were obtained. Increasing the pH value can induce the phase transformation from monazite to zircon type accompanied with the morphology transformation: urchin-like → bundle → nanorod/nanowire. In addition, the concentration of EDTA also played an important role in determining the aspect ratio of tetragonal LaVO4:Eu nanorods. The possible mechanism responsible for the phase control and morphology evolution of the LaVO4:Eu nanocrystals was discussed. Their luminescent properties were systematically studied. It demonstrated that the phase transformation from monazite to zircon type and the increase in the aspect ratio of LaVO4:Eu nanorods resulted in a remarkable improvement of the luminescent properties.