Efficient luminescence emission in both visible and NIR-II regions by Er³⁺ partitioning doping and interfacial energy transfer

Lanthanide-doped nanoparticles (LDNPs) are widely used in biophotonics due to their narrow emission band, long lifetime and broad-spectrum tunable luminescence properties. Usually, photosensitizers for biotherapeutic applications need to be triggered by visible light, while bioimaging requires near-infrared (NIR) light with better penetration. However, it is still challenging to achieve efficient luminescence emission in the visible to second near-infrared (NIR-II, 1000–1700 nm) range simultaneously for multifunctional nanoparticles excited at a single NIR wavelength. Here, a simple NaYF₄:Er/Ce@NaYbF₄:Er@NaYF₄:Nd core-shell-shell nanoparticle with interfacial energy transfer by the Yb-sensitized shell and partition doping of Er³⁺ under 808 nm excitation, which allows the system to achieve visible and NIR-II luminescence emission from different partitions of Er³⁺. When Ce³⁺ is introduced into the core, the Er³⁺ in the Yb-sensitized shell is responsible for the emission in the visible region, while the core-doped Er³⁺ is mainly responsible for the emission at 1550 nm in the NIR-II. In addition, this core-shell-shell nanostructure has a long luminescence emission lifetime in the visible and NIR-II regions, especially the luminescence lifetime of Er³⁺ at 1550 nm is extended to 6.4 ms. More importantly, efficient ¹O₂ generation can be achieved by coupling core-shell-shell nanoparticles with photosensitizer. These results will provide previously unattainable opportunities for LDNPs in biotherapeutic and imaging applications.