Hydrothermally derived NaLuF4:Yb3+, Ln3+ (Ln3+ = Er3+, Tm3+ and Ho3+) microstructures with controllable synthesis, morphology evolution and multicolor luminescence properties†
A series of NaLuF4:Yb3+, Ln3+ (Ln3+ = Er3+, Tm3+, and Ho3+) microstructures with diverse morphologies and sizes were successfully prepared via a designed hydrothermal route with the assistance of trisodium citrate (Na3Cit). The phases, morphologies, sizes and luminescent properties of the as-prepared products were fully characterized by means of X-ray diffraction (XRD), field scanning electron microscopy (FESEM), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX) and up-conversion (UC) photoluminescence spectroscopy, respectively. It can be found that the as-prepared microcrystals can be rationally modified in phase, size and morphology by tuning the pH value, Na3Cit content, and reaction time. Based on the experimental results, the possible formation mechanism of the crystal growth process was proposed. Moreover, a systematic study of the up-conversion (UC) luminescent properties of NaLuF4 has also been performed through doping different rare earth ions (Yb3+/Er3+, Yb3+/Tm3+ and Yb3+/Ho3+). It is found that under 980 nm NIR excitation, the emission intensity and the corresponding luminescent colors of Yb3+/Er3+, Yb3+/Tm3+, and Yb3+/Ho3+ co-doped NaLuF4 can be precisely modulated by changing the Yb3+ doping concentration. These merits of multicolor emissions in the visible region endow this kind of material with potential applications in the fields of light display systems, lasers, and optoelectronic devices.