Lanthanide-doped energy cascade nanoparticles: Full spectrum emission by single wavelength excitation

We describe the use of a layer-by-layer hierarchical nanostructure to exploit the synergy of different lanthanide ions for converting single wavelength excitation into emissions spanning the whole spectral region. By lining up a set of lanthanide ions with matched energy levels in a core-shell nanostructure, we demonstrate well-defined cascades of energy transfer that gives access to optical emissions from a large collection of lanthanide ions (Tb³⁺, Eu³⁺, Dy³⁺, Sm³⁺, Nd³⁺, Yb³⁺, and Er³⁺) after excitation into a common sensitizer of Ce³⁺ featuring a broad absorption. Through optimization of the nanoparticle structure and surface coating, high quantum yields of up to 90% are achieved. Our results highlight that the controlled energy cascades at nanometer scale provide new opportunities for applications such as fighting against counterfeiting and sensing small molecules.