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Overlooked impact of surface hydroxylation on the solubility of less-soluble compounds: a case study of CeO2
Unexpectedly, the solubility of CeO2 nanoparticles (NPs) at 25 °C does not depend on particle size, but is
significantly affected by the sample's thermal pre-treatment. The classical interpretation of NPs' solubility
proposed by the Gibbs–Thompson or Kelvin equations fails to describe the experimental data on CeO2
solubility obtained in this study. Thermal treatment did not change the samples' morphological
characteristics, while slightly affecting NP hydroxylation and local crystallinity. The differences in the
solubility of dried and non-treated CeO2 particles were most noticeable at pH < 4, and dissolved cerium
concentration was much lower in the case of the dried sample. After prolonged storage (up to 4.5 years)
of CeO2 NPs in aqueous media, the solubility of dried samples gradually increased, while for non-treated
samples it remained unchanged. Based on the example of CeO2, the dissolution laws of other less soluble
nanomaterials should be reconsidered.