Tunable multicolor and enhanced red emission of monodisperse CaF2:Yb3+/Ho3+ microspheres via Mn2+ doping

Transition metal ions (e.g. Mn 2+ ) and lanthanide co-doped upconversion (UC) materials have attracted wide attention in recent years due to their promising application in multicolor display. Here, we report the hydrothermal synthesis and characterization of Mn 2+ doped monodisperse CaF 2 :Yb 3+ /Ho 3+ microspheres . The results of X-ray diffraction (XRD) revealed that Mn 2+ doping does not change the cubic phase of CaF 2 material but will lead to diffraction peaks shifting slightly towards higher angle due to the substitution of larger Ca 2+ by the relatively smaller Mn 2+ . Under the excitation of 980 nm continuous wave (CW) laser, these microspheres exhibit green-yellow-red tuning colors and remarkable enhancement of both red to green ratio (R/G) and red to blue ratio (R/B) when increasing Mn 2+ concentration from 0 to 30 mol%. The energy migration process between Ho 3+ and Mn 2+ was proposed and supported by time-decay and power dependence measurements of Ho 3+ UC emission. These upconversion materials may have potential applications in optical devices , color display, nanoscale lasers and biomedical imaging.