Adlershofer Kolloquium Analytik: Microwave-Assisted Synthesis of Lanthanide-based Nanoparticles and their Potential for Opto-Magnetic Applications

Microwave-Assisted Synthesis of Lanthanide-based Nanoparticles and their Potential for Opto-Magnetic Applications
Presenter: Prof. Dr. Eva Hemmer University of Ottawa, Canada

Summary: The remarkable optical properties of the lanthanides (Ln) make Ln-based materials ideal for applications ranging from biomedicine to optoelectronics and energy conversion technology. This is due to the unique electronic properties of the Ln3+ ions allowing for upconversion, i.e., the emission of UV-visible light under near-infrared excitation. Upconverting nanoparticles (UCNPs) based on sodium lanthanide fluorides (NaLnF4) are commonly synthesized by the thermal decomposition of metal precursors in high-boiling-point solvents, based on convectional heating. Microwave reactors can improve reproducibility by offering better control over a reaction environment. More homogeneous heat distribution yields narrow size distributions, and rapid heating to the desired temperature shortens reaction times from hours to minutes.

We developed a fast and reliable microwave-assisted synthetic approach allowing crystalline phase, architectural, and size control of NaLnF4 from sub-3 to ca. 25 nm. Seeking alternative host materials for upconverting Ln3+ dopants, challenges remain: Reproducible microwave-assisted synthesis of LiLnF4 nanoparticles has not yet been shown, while their microscale counterparts were successfully synthesized, and routes towards Gd2O2S have just started to be explored.

This presentation will shed light on the microwave-assisted synthesis as an alternative to established routes and highlight pros and cons of this strategy towards the design of Ln-based particles from the nano- to the microscale.

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