Surface phosphatization of cerium-lanthanum oxides for catalytically inert white pigments

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dc.contributor.authorOnoda, Hiroaki
dc.contributor.authorWada, Takuma
dc.contributor.authorCharoonsuk, Thitirat
dc.contributor.authorPulphol, Phieraya
dc.contributor.authorMuanghlua, Rangson
dc.contributor.authorVittayakorn, Naratip
dc.date.accessioned2026-08-06T10:52:37Z
dc.date.available2026-08-06T10:52:37Z
dc.date.issued2025-11-01
dc.description.abstractCerium dioxide (CeO<inf>2</inf>) is a UV-scattering agent commonly employed in sunscreens but suffers from oxidative catalytic activity, raising concerns for dermal applications. To address this issue, surface passivation via phosphatization has been explored, although prior attempts with CeO<inf>2</inf> alone failed to eliminate its intrinsic yellow hue due to low reactivity with phosphoric acid. In this study, we introduce a novel white pigment synthesized via the phosphoric acid-mediated treatment of CeO<inf>2</inf>–La<inf>2</inf>O<inf>3</inf> mixtures. By co-utilizing lanthanum oxide, which readily forms lanthanum phosphate—a white, inert compound—we achieved enhanced suppression of oxidative activity alongside improved whiteness. The composite materials were systematically characterized via X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), particle size analysis, colorimetry (Lab*), and catalytic activity assays. The results reveal that phosphatization preferentially proceeds at lanthanum sites, forming phosphate-rich surface layers that diminish redox activity while maintaining favorable dispersion and smoothness properties. The pigment shows high acid resistance and negligible photocatalytic activity, indicating its potential as a safe, non-reactive alternative for cosmetic formulations. This work advances the development of rare-earth-based functional pigments via a scalable, low-temperature route.
dc.identifier.citationJournal of Photochemistry and Photobiology A Chemistry, 468, 2025
dc.identifier.doi10.1016/j.jphotochem.2025.116522
dc.identifier.issn10106030
dc.identifier.other2-s2.0-105006697882
dc.identifier.urihttps://dspace.kmitl.ac.th/handle/123456789/17348
dc.sourceJournal of Photochemistry and Photobiology A Chemistry
dc.subjectCerium dioxide
dc.subjectCosmetic pigments
dc.subjectInorganic phosphate
dc.subjectOxidation catalytic activity
dc.titleSurface phosphatization of cerium-lanthanum oxides for catalytically inert white pigments
dc.typeArticle

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