Facile synthesis and size-dependent luminescence of gadolinium compounds with multiform morphologies and tunable particle sizes

A series of monodisperse size-controllable amorphous Gd(OH)CO3 spherical particles with good dispersity have been prepared by a simple homogeneous precipitation route with ethylene glycol (EG) as auxiliary solvent. The average diameters of precursor spheres can be tuned in the range of 70–220 nm by simply changing the volume ratios of EG/H2O in the solvent. In general, the particle size of the spherical particles gradually increases by enhancing the proportion of H2O for the mixing solvent of EG/H2O. Moreover, the long flakes and sheet-like microstructures of the crystalline precursors [Gd2O(CO3)2∙H2O] are obtained by increasing reaction temperature or prolonging reaction time. Thus, the multiform precursors with tunable morphologies and particle sizes have been achieved by systematically adjusting the reaction conditions. It is worth pointing out that the corresponding gadolinium oxide (Gd2O3) products perfectly inherit the good morphology, unifomity, and dispersity of the precursor particles except for a shrinkage in diameters after an annealing process in air, resulting in the uniform and well-dispersed Gd2O3 spheres with tunable particle sizes (50–180 nm). The lanthanide ions (Ln3+) doped samples exhibit their corresponding characteristic down-conversion (DC) or up-conversion (UC) multicolor emissions under UV or NIR excitation. The size-dependent luminescence properties of the Ln3+-doped phosphors are also investigated in detail. The as-manufactured LED device prepared by the phosphor and LED chip can exhibit characteristic emission of activator ion, which directly prove the potential applications of the phosphors in LEDs and optoelectronics. Furthermore, the as-proposed synthesis strategy may provide some insight for the design and fabrication of other rare earth functional materials with controllable morphology and particle sizes.