A lanthanide-doping route to aspect-ratio-controlled KSc2F7 nanocrystals for upconversion, downconversion and magnetism

A novel route was developed by doping rare-earth ions (RE3+) with large ionic radii (such as La3+, Ce3+, Sm3+, Eu3+, Tb3+, Dy3+, Yb3+ and Lu3+) for aspect ratio modification of KSc2F7 nanocrystals (NCs). The results revealed that the shape of the nanocrystals could be readily tuned from one-dimensional long nanorods to zero-dimensional ultrasmall nanospheres. The aspect ratio of the NCs could be adjusted over a broad range from 45 to 1 by changing the dopant or doping concentration. Interestingly it was found that doping of a lanthanide with a larger ionic radius was equivalent to increasing the amount of the dopant on the aspect ratio evolution. The NCs doped with different RE3+ also exhibited multifunctionality, including upconversion (UC) and downconversion (DC) emissions as well as paramagnetic properties.