Uniform Lu2O3hollow microspheres: template-directed synthesis and bright white up-conversion luminescence properties

Abstract

Well-dispersed, uniform Lu2O3 hollow microspheres have been successfully fabricated via a urea-based precipitation method in the presence of colloidal PS microspheres as templates, followed by subsequent heat treatment. The structure, morphology, formation process, and fluorescent properties are well investigated using various techniques. The results indicate that the hollow microspheres can be well indexed to the cubic Lu2O3 phase. The hollow Lu2O3 microspheres with a uniform diameter of about 2.2 μm maintain the spherical morphology and good dispersion of the PS spheres template. The shell of the hollow microspheres consists of numerous nanocrystals with the thickness of approximately 20 nm. Moreover, the possible formation mechanism of evolution from the PS spheres to the amorphous precursor and to the final hollow Lu2O3 microspheres has also been proposed. Under 980 nm laser diode excitation, Lu2O3:Yb3+/Tm3+, Lu2O3:Er3+ and Lu2O3:Yb3+/Er3+ products are mainly dominated by blue, green and red light emissions, respectively. The ratio of the intensity of green luminescence to that of red luminescence decreases with an increase of the concentration of Yb3+ in Lu2O3:Er3+ samples. Furthermore, the UC white light was successfully obtained in the Lu2O3:Yb3+/Er3+/Tm3+ system by adjusting the relative doping concentration of Yb3+, Er3+ and Tm3+. The obtained UC white light has CIE-x = 0.3478 and CIE-y = 0.3143, which are very close to the standard equal energy white light illuminate (x = 0.33, y = 0.33). Because of abundant luminescent colors from RGB to white in Lu2O3:Yb3+/Er3+/Tm3+ samples under 980 nm laser diode (LD) excitation, they can potentially be used as fluorophores in the fields of color displays, backlights, UC lasers, photonics, and biomedicine.