Beam-induced redox chemistry in iron oxide nanoparticle dispersions at ESRF–EBS

Thomä, S.L.J.; Zobel, M.

doi:10.1107/S1600577522011523

Figure 2
Change of the crystalline structure of the IONPs dispersed in an EtOH–H₂O mixture with low EtOH concentration upon irradiation with highly brilliant X-rays. Illustrations of the $[Fd\bar3m]$ unit cells have been made using VESTA (Momma & Izumi, 2011

). Black balls represent oxygen atoms, blue balls represent iron atoms, vacancies are illustrated by partial filling and the red and grey polyhedra illustrate [FeO₆] octahedral and [FeO₄] tetrahedral units, respectively. IONPs before radiation with the X-ray beam are non-stochiometric, but mostly containing Fe³⁺ (see Section S3 of the supporting information), crystallized in inverse spinel structure (here described with $[Fd\bar3m]$ unit cell for simplicity), therefore possessing vacancies on the octahedral sites (left side). Induced by the irradiation with X-rays, both oxidative and reducing radicals are created by radiolysis of water. Due to the presence of EtOH, the oxidative radical $[{\rm{OH}}^{\,\bullet}]$ is scavenged, a reducing atmosphere is created and Fe³⁺ is reduced to Fe²⁺, which fills the vacancies and leads to expansion of the crystal lattice due to its bigger ionic radius (unit cell on the right side).

JOURNAL OF
SYNCHROTRON
RADIATION

ISSN: 1600-5775

Volume 30| Part 2| March 2023| Pages 440-444

https://doi.org/10.1107/S1600577522011523

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