title: Electron small polarons and their mobility in iron (oxyhydr)oxide nanoparticles.
abstract: Electron mobility within iron (oxyhydr)oxides enables charge transfer between widely separated surface sites. There is increasing evidence that this internal conduction influences the rates of interfacial reactions and the outcomes of redox-driven phase transformations of environmental interest. To determine the links between crystal structure and charge-transport efficiency, we used pump-probe spectroscopy to study the dynamics of electrons introduced into iron(III) (oxyhydr)oxide nanoparticles via ultrafast interfacial electron transfer. Using time-resolved x-ray spectroscopy and ab initio calculations, we observed the formation of reduced and structurally distorted metal sites consistent with small polarons. Comparisons between different phases (hematite, maghemite, and ferrihydrite) revealed that short-range structural topology, not long-range order, dominates the electron-hopping rate.
authors.affiliation: Earth Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
authors.forename: Jordan E
authors.initials: JE
authors.lastname: Katz
authors.forename: Xiaoyi
authors.initials: X
authors.lastname: Zhang
authors.forename: Klaus
authors.initials: K
authors.lastname: Attenkofer
authors.forename: Karena W
authors.initials: KW
authors.lastname: Chapman
authors.forename: Cathrine
authors.initials: C
authors.lastname: Frandsen
authors.forename: Piotr
authors.initials: P
authors.lastname: Zarzycki
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Rosso
authors.forename: Roger W
authors.initials: RW
authors.lastname: Falcone
authors.forename: Glenn A
authors.initials: GA
authors.lastname: Waychunas
authors.forename: Benjamin
authors.initials: B
authors.lastname: Gilbert