Effective tuning of the ratio of red to green emission of Ho3+ ions in single LiLuF4 microparticle via codoping Ce3+ ions

Yb3+/Ho3+ codoped LiLuF4 microparticles have been successfully prepared via a facile hydrothermal method. The crystal phase and morphology of LiLuF4 microparticles were inspected by x-ray diffraction and scanning electron microscope, respectively. The upconversion emission of single LiLuF4: Yb3+/Ho3+ microparticle was carefully studied by a confocal microscopy setup under NIR 980 nm excitation. With the increase of Ce3+ ion concentrations of 12%, the ratio of red to green emission of the Ho3+ ions of single LiLuF4 microparticle was boosted about 17-fold, and the output colors were tuned from green to red, which is due to the two efficient cross-relaxation between Ho3+ and Ce3+ ions enhances the red and suppresses the green in the emission processes. To investigate the optical properties of the single microparticle or nanoparticle through the confocal microscopy setup can effectively avoid the influence of surrounding particle or environment, and could provide more precise information for better exploring the emission mechanisms of rare earth ions. The tunable upconversion emission of Ho3+ in single LiLuF4 microparticle in this work will have great potential applications in the micro optoelectronic devices and color display applications.