Size and shape controllable synthesis and luminescent properties of BaGdF5:Ce3+/Ln3+ (Ln = Sm, Dy, Eu, Tb) nano/submicrocrystals by a facile hydrothermal process

Abstract

In this paper, we present a facile and environmentally-friendly hydrothermal process to synthesize BaGdF₅: 2.5 mol% Ce³⁺/2.5 mol% Ln³⁺ (Ln = Sm, Dy, Eu and Tb) nano/submicroparticles. X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), as well as photoluminescence (PL) spectra are used to characterize the resulting samples. The size, shape, and composition of the products could be tuned just by varying the organic additives and the pH values of the initial reaction solutions. The morphologies for the products include nanospheres, submicrospheres, peanut-like particles, as well as the spindle-like and star-like aggregates. Moreover, the size of the samples can be tuned from 50 nm to 150 nm. Additionally, we systematically investigate the luminescence properties of different lanthanide ions in BaGdF₅ host. Under single-wavelength excitation at 260 nm, the samples doped with different lanthanide ions show intensive multicolor visible emissions depending on the doped Ln³⁺ ions. The luminescence process can be attributed to the strong absorption of UV irradiation by Ce³⁺ ions, followed by energy transfer to Gd³⁺ ions, from which the energy is transferred to Ln³⁺, resulting in the emission from the luminescent Ln³⁺ centers. The Gd³⁺ ions play an intermediate role in this process.