Epitaxial Core/Shell Nanocrystals of (Europium-Doped) Zirconia and Hafnia

Carlotta Seno^a, Nico Reichholf^a, Francesco Salutari^b, Maria Chiara Spadaro^b^,^c, Yurii P. Ivanov^d, Giorgio Divitini^d, Alexander Gogos^e^,^f, Inge K. Herrmann^e^,^f, Jordi Arbiol^b^,^g, Philippe F. Smet^h, Jonathan De Roo^a

^aDepartment of Chemistry, University of Basel, Mattenstrasse 22, 4058 Basel, Switzerland

^bCatalan Institute of Nanoscience and Nanotechnology (ICN2), CSIC and BIST, 08193 Barcelona, Catalonia, Spain

^cDepartment of Physics and Astronomy “Ettore Majorana”, University of Catania and CNR-IMM, Via S. Sofia 64, 95123 Catania, Italy

^dElectron Spectroscopy and Nanoscopy, Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova, Italy

^eLaboratory for Particles-Biology Interactions, Department of Materials Meet Life, Swiss Federal Laboratories for Materials Science and Technology (Empa), Lerchenfeldstrasse 5, 9014 St. Gallen, Switzerland

^fNanoparticle Systems Engineering Laboratory, Institute of Process Engineering, Department of Mechanical and Process Engineering, ETH Zurich, Sonneggstrasse 3, 8092 Zurich, Switzerland

^gICREA, 08010 Barcelona, Catalonia, Spain

^hLumiLab, Department of Solid State Sciences, Ghent University, Krijgslaan 281-S1, 9000 Ghent, Belgium

Materials for Sustainable Development Conference (MATSUS)
Proceedings of MATSUS Spring 2025 Conference (MATSUSSpring25)

III-V Quantum Dots and Beyond: Pioneering Core-only and Core-Shell Structures for Future Applications - #III-VQD

Sevilla, Spain, 2025 March 3rd - 7th

Organizers: Ivan Infante and Liberato Manna

Oral, Carlotta Seno, presentation 229
DOI: https://doi.org/10.29363/nanoge.matsusspring.2025.229
Publication date: 16th December 2024

Metal oxides, like ZrO₂ and HfO₂, and fluorides (e.g. NaYF₄ and NaGdF₄), are two classes of nanocrystals serving as hosts for optically active lanthanides ions (e.g. europium).^1-5 While doped fluorides are widely studied and their syntheses are well developed, the oxide hosts struggle with the synthetic challenge of producing colloidally stable nanocrystals with a complex architecture (as for example core/shells). In this work, we pioneer the synthesis of metal oxide core/shell nanocrystals where HfO₂ epitaxially grows onto ZrO₂, confirmed by high resolution transmission electron microscopy images and energy-dispersive Xray spectroscopy compositional maps. Furthermore, the beneficial effect of the shell on the optical properties is established by investigating the photoluminescence of ZrO₂:Eu and of ZrO₂:Eu/ZrO₂ after growing a protective zirconia shell on it. After shelling, the lifetime of the europium doped zirconia nanocrystals increases to 5.3 ± 0.1 ms, showing that we successfully shut down non-radiative pathways. The long lifetime is unprecedented for the high doping percentage (9% Eu). The method has been demonstrated to improve the local environment of europium dopants in zirconia nanocrystals, giving access to novel heterostructures with improved optical properties. This opens up possibilities for their application in different areas, from microelectronics to scintillators.

References:

[1] [1] Ninjbadgar, T.; Garnweitner, G.; Börger, A.; Goldenberg, L. M.; Sakhno, O. V.; Stumpe, J. Synthesis of Luminescent ZrO2:Eu3+ Nanoparticles and Their Holographic Sub-Micrometer Patterning in Polymer Composites. Adv. Funct. Mater. 2009, 19 (11), 1819-1825.

[2] [2] Liu, Y.; Zhou, S.; Tu, D.; Chen, Z.; Huang, M.; Zhu, H.; Ma, E.; Chen, X. Amine-Functionalized Lanthanide-Doped Zirconia Nanoparticles: Optical Spectroscopy, Time-Resolved Fluorescence Resonance Energy Transfer Biodetection, and Targeted Imaging. J. Am. Chem. Soc. 2012, 134 (36), 15083-15090.

[3] [3] A. Lauria, A.; Villa, I.; Fasoli, M.; Niederberger, M.; Vedda, A. Multifunctional Role of Rare Earth Doping in Optical Materials: Nonaqueous Sol–Gel Synthesis of Stabilized Cubic HfO2 Luminescent Nanoparticles. ACS Nano 2013, 7 (8), 7041-7052.

[4] [4] Zheng, B.; Fan, J.; Chen, B.; Qin, X.; Wang, J.; Wang, F.; Deng, R.; Liu, X; Rare-Earth Doping in Nanostructured Inorganic Materials. Chem. Rev. 2022, 122 (6), 5519-5603.

[5] [5] Gai, S.; Li, C.; Yang, P.; Lin, J. Recent Progress in Rare Earth Micro/Nanocrystals: Soft Chemical Synthesis, Luminescent Properties, and Biomedical Applications. Chem. Rev. 2014, 114 (4), 2343-2389.

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