Engineering Energy Flow in Ho³⁺-Doped Upconversion Nanoparticles: Multilayer Design for Overcoming Concentration...

Area of Science:

• Materials Science
• Nanotechnology
• Photonics

Background:

• Upconversion nanoparticles (UCNPs) exhibit unique anti-Stokes luminescence and photostability.
• Holmium-activated (Ho³⁺) UCNPs often show low luminescence efficiency due to complex energy levels and nonradiative decay.

Purpose of the Study:

• To overcome efficiency limitations in Ho³⁺-activated UCNPs.
• To develop a generalizable design for advanced luminescent materials with tunable optoelectronic properties.

Main Methods:

• Designed a multilayer core-shell architecture for spatial separation of sensitizers and activators.
• Controlled intermediate layer thickness to optimize energy transfer kinetics.
• Incorporated Neodymium (Nd³⁺) as an outer sensitization layer and Cerium (Ce³⁺) for spectral modulation.

Main Results:

• Achieved enhanced photon harvesting and mitigated thermal effects using an Nd³⁺ sensitization layer.
• Enabled dynamic spectral modulation between green and red emissions via Ce³⁺ doping and cross-relaxation.
• Substantially increased the upconversion quantum yield of the UCNPs.

Conclusions:

• The multilayer core-shell design effectively enhances UCNP luminescence efficiency.
• This strategy provides a versatile platform for creating next-generation luminescent materials with tailored characteristics.