Two birds with one stone: Versatile lanthanide-doped core-shell-shell nanoparticles with enhanced red upconversion...

Lanthanide-doped fluoride nanoparticles show great potential for optical thermometry and bioimaging. However, their applications are still constrained by inherent limitations in luminescence intensity and functional versatility. To overcome these challenges, we propose a core-active shell-inert shell nanostructure that integrates multifunctional capabilities within a single platform. These nanoparticles exhibit intense red upconversion luminescence under 980 nm excitation. They concurrently enable multimodal nanothermometry through three distinct mechanisms: thermally coupled energy levels, non-thermally coupled energy levels, and chromaticity shifting. Additionally, it has potential for magnetic resonance (MR) imaging functionality. The active shell enhances luminescent properties, whereas the inert shell facilitates MR contrast. This work establishes a design paradigm for multifunctional nanoprobes unifying upconversion luminescence, nanothermometry, and MR imaging capabilities.