Tetragonal (Y,Ln)PO_4·nH_2O (Ln = Tb/Eu) colloidal spheres for color tunable photoluminescence and the effects of hydration

摘要

Tetragonal-structured colloidal spheres of Y/Eu binary and Y/Tb/Eu ternary phosphate hydrates have been successfully synthesized via microwave-assisted homogeneous precipitation, and the effects of hydrate water on crystal structure and luminescent behavior were investigated by detailed characterizations of XRD, Raman, FE-SEM, HR-TEM, STEM, PLE/PL spectroscopy, and fluorescence decay analysis. Decreasing the hydrate water induced more PO43- shifting from symmetric stretching vibration to anti-symmetric one, along with lattice expansion. Dehydration leads to a blue shift of the maximum band centre in the PLE spectra of Y/Eu binary phosphate. Both the hydrate and anhydrous spheres of Y/Tb/Eu ternary phosphates exhibited color-tunable emissions from green to red by increasing the Eu content. However, stronger quenching effect of hydrate water on Eu3+ transition than that on Tb3+ one takes place, and the emission at longer wavelength, especially for the near-infrared region, is significantly affected by the hydrate water. The hydrate water did not significantly affect the Tb3+- Eu3+ energy transfer efficiency, but it could shorten the lifetimes.