title: Characterization of cerium oxide nanoparticles-part 2: nonsize measurements.
abstract: Part 1 (see companion paper) of the present study discussed the application of a multimethod approach in characterizing the size of cerium oxide nanoparticles (NPs). However, other properties less routinely investigated, such as shape and morphology, structure, chemical composition, and surface properties, are likely to play an important role in determining the behavior, reactivity, and potential toxicity of these NPs. The present study describes the measurement of the aforementioned physicochemical properties of NPs (applied also to nanomaterials [NMs]) compared with micrometer particles (MPs). The authors use a wide range of techniques, including high resolution-transmission electron microscopy, scanning electron microscopy, atomic force microscopy, X-ray diffraction, X-ray energy dispersive spectroscopy, electron energy loss spectroscopy, X-ray photoelectron spectroscopy, and electrophoresis, and compare these techniques, their advantages, and their limitations, along with recommendations about how best to approach NM characterization, using an application to commercial cerium oxide NPs and MPs. Results show that both cerium oxide NPs and MPs are formed of single polyhedron or truncated polyhedron crystals. Cerium oxide NPs contain a mixture of Ce(3+) and Ce(4+) cations, whereas the MPs contain mainly Ce(4+) , which is potentially important in understanding the toxicity of cerium oxide NPs. The isoelectric point of cerium oxide NPs was approximately pH 8, which explains their propensity to aggregate in aqueous media (see companion paper).
authors.affiliation: School of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, United Kingdom. m.a.baalousha@bham.ac.uk
authors.forename: Mohammed
authors.initials: M
authors.lastname: Baalousha
authors.forename: Yon
authors.initials: Y
authors.lastname: Ju-Nam
authors.forename: Paula A
authors.initials: PA
authors.lastname: Cole
authors.forename: Joseph A
authors.initials: JA
authors.lastname: Hriljac
authors.forename: Ian P
authors.initials: IP
authors.lastname: Jones
authors.forename: Charles R
authors.initials: CR
authors.lastname: Tyler
authors.forename: Vicki
authors.initials: V
authors.lastname: Stone
authors.forename: Teresa F
authors.initials: TF
authors.lastname: Fernandes
authors.forename: Mark A
authors.initials: MA
authors.lastname: Jepson
authors.forename: Jamie R
authors.initials: JR
authors.lastname: Lead
mesh_terms: D002412:Cations / Q000032:analysis / Q000737:chemistry; D002563:Cerium / Q000032:analysis / Q000737:chemistry*; D007526:Isoelectric Point; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D053758:Nanoparticles / Q000032:analysis / Q000737:chemistry* / Q000648:ultrastructure; D013057:Spectrum Analysis; D013499:Surface Properties; D014961:X-Ray Diffraction
chemical_list: D002412:Cations; D002563:Cerium; C030583:ceric oxide