Lanthanide-doped inorganic nanocrystals typically comprise an insulating host material and lanthanide dopant ions embedded in the host lattice.The luminescence of lanthanide-doped nanocrystals primarily originates from intra-configurational 4f electron transitions within the localized dopant ions.In stark contrast to quantum dots, quantum confinement effects are typically not expected in lanthanide-doped nanocrystals due to small Bohr radius of the exciton in the host, as well as weak interaction between the 4f electrons of the dopant ions and the host material.