Catalysis Enhancement of Ceria Nanoparticles Embedded in Silica‐Nanoparticle Assemblies for Organophosphate Hydrolysis

Cerium dioxide nanoparticles (CeO 2 NPs) have been reported to act as active species for various catalytic reactions including organophosphate hydrolysis. The catalytic activity of CeO 2 NPs embedded in silica nanoparticles assemblies (SiO 2 NPAs) for p ‐nitrophenylphosphate ( p ‐NPP) hydrolysis was enhanced to maintain high dispersity. CeO 2 NPs capped with oleylamine with a size of 15–40 nm showed the low initial rate (<30 min) of 0.71 mM h −1 in a HEPES buffer containing p ‐NPP (8.0 mM) at 60 °C. CeO 2 NPs calcined at 800 °C showed the increased initial rate of 1.1 mM −1 by removal of oleylamine, although CeO 2 NPs partially sintered. Conventional SiO 2 support was used for suppression of the sintering, however, the initial rate decreased to 0.75 mM h −1 by high contact between CeO 2 and SiO 2 . SiO 2 NPAs were used to minimize contact between CeO 2 and SiO 2 . The initial rate with CeO 2 /SiO 2 NPAs prepared by the impregnation method was as high as 1.8 mM h −1 . Furthermore, the initial rate with CeO 2 /SiO 2 NPAs prepared by a premixed method increased to 2.6 mM h −1 by effective suppression of both CeO 2 NPs aggregation and electronic interaction with SiO 2 . Although the sintering of CeO 2 NPs was effectively suppressed even at 1000 °C, the initial rate decreased because of the adsorption of p ‐NPP on SiO 2 NPAs.