/ Muhammed Jibin Parammal
Lighting Up Zirconia: Eliminating and Seeing Surface Emission in Luminescent Nanomaterials
(left) time-resolved emission spectrum of 10% europium doped ZrO2 nanocrystals, normalized at 607 nm. The insert is a TEM image of the particles. (middle) The resulting spectra and decay for bulk and surface ions gained by non-negative matrix factorization. (right) Time resolved emission spectra of the nanocrystals which are shelled with an inert layer of zirconia, normalized at 607 nm, with respective TEM image (graphics: University of Basel, Nico Reichholf).
In nanomaterials, surface phenomena play a crucial role — and luminescence is no exception. Our recent research shows that by carefully engineering zirconia (ZrO₂) nanocrystals doped with lanthanide ions such as europium (Eu³⁺, shown in the figure) and terbium (Tb³⁺), we can suppress the nonradiative “deactivation pathways” that normally quench their light emission.
Lanthanide-doped nanocrystals are exciting candidates for applications ranging from bioimaging and sensing to lighting and quantum technologies, thanks to their sharp and stable emission colours. However, when these dopant ions sit near the nanocrystal surface, they interact with surrounding molecules. This leads to a drainage of their energy before it can be released as light, and a change in the emitted wavelengths.
To address these detrimental effects, we synthesized both core-only and core/shell zirconia nanocrystals and analysed their light emission using time-resolved spectroscopy combined with machine learning for data analysis (non-negative matrix factorization). This allowed us to disentangle and identify the fast-decaying surface emission from the long-lived bulk emission. When the nanocrystals were coated with a zirconia shell, the surface contribution vanished completely — leading to brighter and purer luminescence.
This finding demonstrates that surface engineering is the key to unlocking the full potential of lanthanide-doped zirconia nanocrystals. By suppressing deactivation at the surface, we open new opportunities for designing highly efficient light-emitting nanomaterials. Looking ahead, such tailored nanocrystals could find use in advanced optical devices and biomedical imaging probes.
Original publication
Nico Reichholf, Sharona Horta, David Van der Heggen, Carlotta Seno, Jikson Pulparayil Mathew, Maria Ibáñez, Philippe F. Smet, Jonathan De Roo
Identification and Elimination of Surface Emission in Lanthanide (Co)doped Zirconia Nanocrystals
ACS Nano2025, doi: 10.1021/acsnano.5c09137
Further Information
Webseite research group Prof. Jonathan De Roo
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