Fig. 4: Schematic illustration of the structures and energy transfer pathways of different NCs.

The structures of a dimeric, b EuF₃&GdF₃, and c EuF₃&2GdF₃ NCs. d Core-shelled, e EuF₃@GdF₃, and f EuF₃@GdF₃@GdF₃ NCs. g Reversely core-shelled, h GdF₃@EuF₃, and i GdF₃@EuF₃@EuF₃ NCs, as well as their respective energy transfer pathways. b, c, e, f and h, i illustrate the energy transfer details in differently structured NCs using 273 nm light to excite Gd³⁺, which transfers energy to Eu³⁺ (Supplementary Fig. 11). Note: for simplicity, energy migrations between Gd³⁺–Gd³⁺ and Eu³⁺–Eu³⁺ were not shown.