A series of Er3+and Ho3+ion-doped NaYF4core-shell microcrystals were synthesized by the hydrothermal synthesis method and epitaxial growth technology, the structure and morphology of the core-shell microcrystals were characterized by SEM and XRD. Under the excitation of near-infrared light at 980 nm, the upconversion emission characteristics of single-particle NaYF4: Yb3+/Er3+, NaYF4: Yb3+/Ho3+core-shell microrods were studied with a confocal microscope spectroscopy device. The experimental results show that when the NaYF4 inert shell is coated, the core-shell growth direction is along the longitudinal axis and the upconversion emission intensity is significantly enhanced. The main reason is that the NaYF4inert shell can effectively inhibit the surface quenching effect of micron particles. However, when it is coated with the NaYbF4active shell, the micron core-shell grows along the horizontal axis, and its upconversion emission intensity is also enhanced, the enhancement factor is lower than that of the coated inert shell.It can be found that the red-green ratio of the upconversion emission of Er3+and Ho3+ions with different core-shell structures show different phenomena. When the NaYbF4active shell is coated, the red-green ratio of Er3+ions is significantly increased, while the red-green ratio of Ho3+ions is significantly reduced. It can be found that the construction of different core-shell structures can not only enhance upconversion luminescence, but also achieve effective control of emission.

upconversion; core-shell structures; single-particles; luminescence regulation