Hydrothermal synthesis and optical properties of Eu3+ doped NaREF4 (RE = Y, Gd), LnF3 (Ln = Y, La), and YF3·1.5NH3 micro/nanocrystals

5 mol% Eu3+ doped NaYF4 (α-, β-), YF3, YF3·1.5NH3, NaGdF4, and LaF3 micro/nanocrystals have been synthesized by a hydrothermal method. The final products are characterized by X-ray diffraction, field emission scanning electron microscopy, photoluminescence excitation and emission spectra, and luminescent dynamic decay curves. Due to its sensitivity to local symmetry, Eu3+ shows different optical properties in the above samples. It has stronger luminescent intensity in β-NaYF4 than that in α-NaYF4 while it exhibits different higher energy 5D1,2 to lower 7FJ emissions as well as the asymmetric ratios and the splits of 5D0 → 7F1, 7F4. YF3, LaF3, and β-NaGdF4 have analogous optical intensities to those of β-NaYF4. However, β-NaGdF4 has the similar spectral profile to that of β-NaYF4 while YF3 and LaF3 have the opposite cases in the 5D0 → 7F2, 7F1 emissions. Further, Judd–Ofelt calculation has been used to analyze the experimental phenomena.