Multicolor upconversion emission of dispersed ultrasmall cubic Sr2LuF7 nanocrystals synthesized by a solvothermal process

Lanthanide (Ln3+) doped Sr2LuF7 (Ln3+=Er3+/Tm3+/Yb3+) nanocrystals (NCs) were synthesized via a solvothermal process using oleate as stabilizing agent. The as-synthesized NCs with a mean diameter of sub-20 nm can be well dispersed in cyclohexane and show a pure cubic phase structure with space group image. Following appropriate lanthanide ion doping, the NCs show intense red, green, blue and white-color upconversion emission (UC) under the excitation of a 980 nm laser. Predominant near-infrared UC can also be obtained in the Yb3+/Tm3+ doped Sr2LuF7 NCs. The energy transfer UC mechanisms for the fluorescent intensity were also investigated. The desirable property of the ultrasmall dispersed NCs makes them promising materials for the applications in miniaturized solid-state light sources, multicolor three-dimensional display devices and fluorescent labels for biomedical imaging.