The effect of surface coating on energy migration-mediated upconversion

Area of Science:

• Materials Science
• Nanotechnology
• Optics

Background:

• Lanthanide-doped upconversion nanoparticles (UCNPs) are investigated for applications in data storage, bioimaging, and drug delivery.
• Surface quenching of excitation energy often limits the efficiency of UCNPs.

Purpose of the Study:

• To design and synthesize novel core-shell UCNPs with improved optical properties.
• To investigate strategies for preventing surface quenching and enhancing luminescence efficiency.

Main Methods:

• Rational design and synthesis of NaGdF(4)@NaGdF(4) core-shell UCNPs.
• Epitaxial growth of an optically inert NaYF(4) shell.
• Characterization of optical properties and mechanistic investigations.

Main Results:

• The NaYF(4) shell effectively prevents surface quenching of excitation energy.
• Tunable upconversion emissions were achieved with various activators (Dy(3+), Sm(3+), Tb(3+), Eu(3+)) at low doping concentrations.
• Efficient emissions from Tb(3+) and Eu(3+) were realized for the first time with homogeneous doping.

Conclusions:

• The developed core-shell UCNPs exhibit unprecedented optical properties due to the inert shell.
• This strategy offers efficient energy migration and trapping, leading to enhanced luminescence.
• These advanced luminescent nanomaterials hold promise for significant biological and energy applications.