title: Surface-mediated formation of Pu(IV) nanoparticles at the muscovite-electrolyte interface.
abstract: The formation of Pu(IV)-oxo-nanoparticles from Pu(III) solutions by a surface-enhanced redox/polymerization reaction at the muscovite (001) basal plane is reported, with a continuous increase in plutonium coverage observed in situ over several hours. The sorbed Pu extends >70 Å from the surface with a maximum concentration at 10.5 Å and a total coverage of >9 Pu atoms per unit cell area of muscovite (0.77 μg Pu/cm(2)) (determined independently by in situ resonant anomalous X-ray reflectivity and by ex-situ alpha-spectrometry). The presence of discrete nanoparticles is confirmed by high resolution atomic force microscopy. We propose that the formation of these Pu(IV) nanoparticles from an otherwise stable Pu(III) solution can be explained by the combination of a highly concentrated interfacial Pu-ion species, the Pu(III)-Pu(IV) redox equilibrium, and the strong proclivity of tetravalent Pu to hydrolyze and form polymeric species. These results are the first direct observation of such behavior of plutonium on a naturally occurring mineral, providing insights into understanding the environmental transport of plutonium and other contaminants capable of similar redox/polymerization reactions.
authors.affiliation: Chemical Sciences and Engineering Division, Argonne National Laboratory , Argonne , Illinois 60439, United States.
authors.forename: Moritz
authors.initials: M
authors.lastname: Schmidt
authors.forename: Sang Soo
authors.initials: SS
authors.lastname: Lee
authors.forename: Richard E
authors.initials: RE
authors.lastname: Wilson
authors.forename: Karah E
authors.initials: KE
authors.lastname: Knope
authors.forename: Francesco
authors.initials: F
authors.lastname: Bellucci
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Eng
authors.forename: Joanne E
authors.initials: JE
authors.lastname: Stubbs
authors.forename: L
authors.initials: L
authors.lastname: Soderholm
authors.forename: P
authors.initials: P
authors.lastname: Fenter
mesh_terms: D000327:Adsorption; D000538:Aluminum Silicates / Q000737:chemistry*; D004573:Electrolytes / Q000737:chemistry*; D004583:Electrons; D018625:Microscopy, Atomic Force; D053758:Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D010084:Oxidation-Reduction; D011005:Plutonium / Q000737:chemistry*; D012996:Solutions; D013499:Surface Properties; D013997:Time Factors; D056928:X-Ray Absorption Spectroscopy
chemical_list: D000538:Aluminum Silicates; D004573:Electrolytes; D012996:Solutions; C517971:muscovite; D011005:Plutonium