Surface versus volume effects in luminescent ceria nanocrystals synthesized by an oil-in-water microemulsion method
2011 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 13, no 38, 17135-17145 p.Article in journal (Refereed) Published
Pure and europium (Eu(3+)) doped cerium dioxide (CeO(2)) nanocrystals have been synthesized by a novel oil-in-water microemulsion reaction method under soft conditions. In-situ X-ray diffraction and RAMAN spectroscopy, high-resolution transmission electron microscopy, UV/Vis diffuse-reflectance and Fourier transform infrared spectroscopy as well as time-resolved photoluminescence spectroscopy were used to characterize the nanaocrystals. The as-synthesized powders are nanocrystalline and have a narrow size distribution centered on 3 nm and high surface area of similar to 250 m(2) g(-1). Only a small fraction of the europium ions substitutes for the bulk, cubic Ce(4+) sites in the europium-doped ceria nanocrystals. Upon calcination up to 1000 degrees C, a remarkable high surface area of similar to 120 m(2) g (-1) is preserved whereas an enrichment of the surface Ce(4+) relative to Ce(3+) ions and relative strong europium emission with a lifetime of similar to 1.8 ms and FWHM as narrow as 10 cm(-1) are measured. Under excitation into the UV and visible spectral range, the europium doped ceria nanocrystals display a variable emission spanning the orange-red wavelengths. The tunable emission is explained by the heterogeneous distribution of the europium dopants within the ceria nanocrystals coupled with the progressive diffusion of the europium ions from the surface to the inner ceria sites and the selective participation of the ceria host to the emission sensitization. Effects of the bulk-doping and impregnation with europium on the ceria host structure and optical properties are also discussed.
Place, publisher, year, edition, pages
2011. Vol. 13, no 38, 17135-17145 p.
oxide nanoparticles, ceo2 nanocrystals, mixed oxides, heterogeneous catalysis, thin-films, raman, size, photoluminescence, defects, area
IdentifiersURN: urn:nbn:se:kth:diva-43445DOI: 10.1039/c1cp21135hISI: 000295128000026ScopusID: 2-s2.0-80053240486OAI: oai:DiVA.org:kth-43445DiVA: diva2:448392
QC 201110172011-10-172011-10-172012-03-19Bibliographically approved