Cerium oxide nanoparticles: Size-selective formation and structure analysis

TLDR

Lattice expansion in cerium oxide nanoparticles is attributed to higher point defect concentrations as particle size decreases. Cerium oxide nanoparticles (±15 % size spread) are synthesized by mixing cerium nitrate with ammonium reagent, and their size is monitored by TEM and photon absorption. High‑resolution TEM shows that over 99 % of the particles are single crystals, while X‑ray diffraction and Raman spectroscopy reveal a lattice parameter increase of up to 0.45 % as particle size shrinks to 6 nm, indicating a size‑dependent lattice expansion.

Abstract

Nanoparticles of cerium oxide with a narrow size distribution (±15%) are prepared by mixing cerium nitrate solution with an ammonium reagent. High-resolution transmission electron microscopy (TEM) indicates that over 99% of the synthesized particles are single crystals. TEM and photon absorption are used to monitor particle size. The lattice parameter increases up to 0.45% as the particle size decreases to 6 nm, as observed with x-ray diffraction. Raman spectra also suggest the particle-size effect and concomitant lattice expansion. The lattice expansion can be explained by increased concentrations of point defects with decreasing particle size.