Size Dependence of Lattice Parameter and Electronic Structure in CeO 2 Nanoparticles

TL;DR

This study investigates how the crystal and electronic properties of CeO2 nanoparticles vary with size, revealing size-dependent lattice parameters and electronic state changes using advanced spectroscopic techniques.

Contribution

It provides new insights into the size-dependent structural and electronic properties of CeO2 nanoparticles through combined experimental and theoretical analysis.

Findings

Lattice parameter varies with nanoparticle size due to surface adsorbed species.

Electronic states, specifically t2g states, depend on nanoparticle size.

CeO2 nanoparticles predominantly contain CeIV ions in a fluorite structure.

Abstract

Intrinsic properties of a compound (e.g., electronic structure, crystallographic structure, optical and magnetic properties) define notably its chemical and physical behavior. In the case of nanomaterials, these fundamental properties depend on the occurrence of quantum mechanical size effects and on the considerable increase of the surface to bulk ratio. Here, we explore the size dependence of both crystal and electronic properties of CeO2 nanoparticles (NPs) with different sizes by state-of-the art spectroscopic techniques. X-ray diffraction, X-ray photoelectron spectroscopy, and high-energy resolution fluorescence-detection hard X-ray absorption near-edge structure (HERFD-XANES) spectroscopy demonstrate that the as-synthesized NPs crystallize in the fluorite structure and they are predominantly composed of CeIV ions. The strong dependence of the lattice parameter with the NPs size was attributed to the presence of adsorbed species at the NPs surface thanks to Fourier transform infrared spectroscopy and thermogravimetric analysis measurements. In addition, the size dependence of the t2g states in the Ce LIII XANES spectra was experimentally observed by HERFD-XANES and confirmed by theoretical calculations.