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arXiv · 2503.22433

Plasmon-Induced Tuning of Cerium Oxidation States in Au@CeO$_x$ Core@Shell Nanoparticles

Klára Beranová·Kevin C. Prince·Mariana Klementová·Marek Vronka·Oleksandr Romanyuk
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Abstract

CeO$_x$-based nanoforms are widely used in catalysis, or biomedical applications due to their redox activity and oxygen storage capacity. The key parameters determining their surface chemistry are the Ce$^{3+}$/Ce$^{4+}$ ratio and the ability to transition between Ce$^{4+}$ and Ce$^{3+}$ states. We synthesized Au@CeO$_x$ core@shell nanoparticles with different thicknesses of CeO$_x$ shells and different Ce$^{3+}$/Ce$^{4+}$ ratios through a photothermal reaction driven by localized surface plasmon resonances (LSPRs) at the Au nanoparticle surface induced by visible light. We introduce a way to further enhance the Ce$^{3+}$/Ce$^{4+}$ ratio in the shell by exposing the Au@CeO$_x$ nanoparticles to visible light using a green laser (532 nm, 50 mW). Our findings based on photoelectron spectroscopy indicate that the Ce$^{4+}$-to-Ce$^{3+}$ transition results from LSPR-induced superheating of the Au@CeO$_x$ interface, leading to the formation of oxygen vacancies and reduction of Ce$^{4+}$ ions. This process is reversible upon air exposure suggesting that the ability to transition between the Ce$^{4+}$ and Ce$^{3+}$ states is retained in the Au@CeO$_x$ nanoparticles. Our study presents the CeO$_x$-based nanoforms with a tunable cerium valence state ratio, highlighting the potential of plasmonic control in optimizing their photocatalytic and enzyme-mimetic properties.

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Klára Beranová, Kevin C. Prince, Mariana Klementová, Marek Vronka, Oleksandr Romanyuk. 2025-03-28. Plasmon-Induced Tuning of Cerium Oxidation States in Au@CeO$_x$ Core@Shell Nanoparticles. https://doi.org/10.1063/5.0272916

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