Interface Energy Tuning in Lanthanide Upconversion Nanoparticles through a Multilayer Growth Strategy.

Area of Science:

• Nanotechnology
• Materials Science
• Biomedical Optics

Background:

• Lanthanide-doped upconversion nanoparticles (UCNPs) convert near-infrared (NIR) light to higher-energy emissions, ideal for biomedical uses due to low autofluorescence and deep tissue penetration.
• Surface-related quenching effects and lack of atomic-level precision in conventional core-shell structures limit UCNP efficiency and application scope.
• Precise control over interfacial energy transfer is crucial for advanced UCNP applications like multiplexed imaging and sensing.

Purpose of the Study:

• To introduce a one-pot successive layer-by-layer (SLBL) strategy for fabricating multilayer UCNPs with atomic-level precision.
• To demonstrate the concept of "interface energy tuning" for enhanced UCNP performance and novel functionalities.
• To explore the potential of precisely engineered UCNPs in multiplexed optogenetics, human vision, and NIR-II bioimaging.

Main Methods:

• Developed a versatile one-pot successive layer-by-layer (SLBL) strategy for controlled epitaxial growth of UCNP shells.
• Utilized precise reaction kinetics to manipulate shell growth and achieve atomic-level control over nanostructure fabrication.
• Engineered multilayer UCNP systems with specific lanthanide dopant arrangements for tailored optical properties.

Main Results:

• Achieved orthogonal trichromatic upconversion luminescence from single nanoparticles, enabling multiplexed optogenetic neuromodulation and NIR light vision.
• Designed novel Er³⁺-, Tm³⁺-, and Ho³⁺-sensitized UCNPs with efficient NIR-II (1000-2000 nm) excitation through precise multilayer engineering.
• Demonstrated in vivo applications including real-time ratiometric biosensing, high-throughput multiplexed imaging, and dynamic visualization in animal models.

Conclusions:

• The SLBL strategy provides unprecedented control over UCNP interfacial energy transfer, transforming interfaces into programmable energy landscapes.
• Precisely engineered multilayer UCNPs unlock advanced biomedical applications, including multiplexed imaging and sensing in the NIR-II window.
• This work offers a rational design framework for next-generation programmable photonic nanodevices for cutting-edge biomedical research.