Two-Phase Synthesis of Colloidal Annular-Shaped CexLa1-xCO3OH Nanoarchitectures Assemblied from Small Particles and Their Thermal Conversion to Derived Mixed Oxides

Undoped and cerium doped LaCO3OH annular-shaped nanoarchitectures with high specific surface area have been fabricated via the thermolysis of CexLa1-x(oleate)(3) (x = 0-20 mol %) complexes in a toluene-water system containing tert-butylamine/oleylamine. The products exhibit 400 nm-sized monodisperse annular-shaped nanoarchitectures, which are constituted of 3-5 nm-sized primary particles. A possible mechanism of the reaction of CexLa1-x(oleate)(3) and terf-butylamine for the formation of annular-shaped CexLa1-xCO3OH nanoarchitectures is proposed. The thermal conversion of CexLa1-xCO3OH to CexLa1-x(CO3)O-2 at 600 degrees C, to CexLa1-x(OH)(3) at 800 degrees C, final to (CexLa1-x)(2)O3-delta at 900 degrees C were employed, while the original morphology was essentially unchanged. The dopant concentration was varied from 5 to 20 of cerium ions per LaCO3OH nanoparticle. The X-ray diffraction (XRD) results reveal that the cerium dopant could enter easily into the LaCO3OH structural lattice, whereas copper could unlikely enter into their lattice because of their large ionic radius difference. The cerium oxidation state was controlled by changing doping concentration. The X-ray photoelectron spectroscopy (XPS) results reveal that only one Ce3+ oxidation state is in the as-synthesized CexLa1-xCO3OH samples with cerium concentration ranging from 5 to 20 mol %, whereas both 3+ and 4+ ones coexisted in 20 mol % Ce:LaCO3OH structure. Remarkable luminescence emission intensity enhancement of 1.5-9.0 times were observed for CexLa1-xCO3OH samples with cerium concentration ranging from 5 to 20 mol %, after doping with an undoped LaCO3OH.