Hybrid dandelion-like YH(O3PC6H5)2:Ln (Ln = Eu3+, Tb3+) particles: formation mechanism, thermal and photoluminescence properties

Abstract

Lanthanide (Ln)-doped yttrium phenylphosphonate nanohybrids with an ordered dandelion-like morphology were synthesized by a simple citric acid-assisted hydrothermal process. The crystal structure, morphology and composition of the as-synthesized products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy and elemental analysis. The formation mechanism of self-assembled dandelion-like particles was demonstrated in detail on the basis of the morphological dependence of the as-synthesized products as a function of the concentration of the organic additive. Thermogravimetry/differential thermal analysis (TG/DTA) showed that the organic–inorganic hybrid structure is preserved until 450 °C, indicating the high thermal stability of the phenylphosphonate-based hybrids. Upon UV excitation, Ln (Eu³⁺, Tb³⁺)-doped phenylphosphonate-based hybrids exhibit emission in the visible region due to an efficient energy transfer from phenyl rings to luminescent Ln centers. The photoluminescence characteristics of samples synthesized with and without citric acid were further quantified through the estimation of the absolute emission quantum yield. The maximum quantum yield value was attained for dandelion-shaped samples synthesized with citric acid, showing an increase of ∼50% in comparison to that of the platelet-like sample synthesized without citric acid. This indicates that the photoluminescence properties can be improved by the tunable morphology.