Controllable hydrothermal synthesis of Eu3+/Tb3+/Dy3+ activated Zn8[(BO3)3O2(OH)3] micro/nanostructured phosphors: energy transfer and tunable emissions

Abstract

A series of novel Tb³⁺, Dy³⁺ single-doped and Eu³⁺/Tb³⁺, Tb³⁺/Dy³⁺ co-doped Zn₈[(BO₃)₃O₂(OH)₃](ZBH) micro/nano structured phosphors have been prepared under hydrothermal conditions without employing any template or surfactant. X-ray diffraction (XRD), scanning electron microscopy (SEM), field transmittance electron microscopy (FTEM), photoluminescence spectroscopy (PL) and fluorescent decay times were used to characterize the as-prepared samples. The XRD, SEM and TEM results indicate that the doped concentration of RE (rare earth) ions can change the crystallinity and morphology of the matrix. The PL results indicate that ZBH:Tb³⁺ is a good green phosphor. When Eu³⁺ and Tb³⁺ ions are co-doped into the ZBH matrix, the phosphor yielded tunable emissions including tri-band established white light emission based on the co-doped RE concentration and excitation wavelength, which was confirmed by the calculated Commission International de l'Eclairage chromaticity coordinates of Eu³⁺/Tb³⁺ co-doped ZBH phosphors. When Dy³⁺ and Tb³⁺ ions are co-doped into the ZBH matrix, Tb³⁺ emission is sensitized by Dy³⁺ through a non-radiative resonant energy transfer, and there also exists energy transfer from the matrix to Dy³⁺ under UV excitation including in the single-doped sample. The energy transferred from Tb³⁺ to Eu³⁺ ions, Dy³⁺ to Tb³⁺ and Tb³⁺ back to Dy³⁺ was controlled by selecting a suitable excitation wavelength, and decay measurements were carried out to analyze the energy transfer efficiency.