Controlled synthesis and luminescent properties of DyPO₄:Eu nanostructures

In this paper, a simple hydrothermal method was designed for the selective synthesis of Eu-doped tetragonal DyPO₄ and hexagonal DyPO₄·1.5H₂O nanocrystals. It was found that the hydrothermal conditions (temperature and pH) and organic additive are very important in determining the crystal structures and morphology of the final products. Low temperature and low pH (120 °C, pH = 2) are favorable for the formation of the hexagonal DyPO₄·1.5H₂O, while high temperature and high pH (200°C, pH = 8) would be more suitable for the production of tetragonal DyPO₄. When the organic additive ethylenediamine tetraacetic acid disodium salt (EDTA) was used, products with the same crystal structures (hexagonal DyPO₄·1.5H₂O) and different morphologies, such as nano/submicroprisms, and nanorods could be obtained. Furthermore, the luminescent properties of DyPO₄:Eu with different crystal structures and morphologies were also investigated. Compared with the hexagonal DyPO₄·1.5H₂O, a small blue shift of the strongest excitation peak and increase in the intensity of the emission spectra can be observed for the tetragonal DyPO₄. Our capability of obtaining hexagonal DyPO₄·1.5H₂O and tetragonal DyPO₄ can not only provide some new information in the study of polymorph control and selective synthesis of inorganic materials, but also benefits the wide applications of DyPO₄ due to the improved luminescent properties.