title: Size-dependent redox behavior of iron observed by in-situ single nanoparticle spectro-microscopy on well-defined model systems.
abstract: Understanding the chemistry of nanoparticles is crucial in many applications. Their synthesis in a controlled manner and their characterization at the single particle level is essential to gain deeper insight into chemical mechanisms. In this work, single nanoparticle spectro-microscopy with top-down nanofabrication is demonstrated to study individual iron nanoparticles of nine different lateral dimensions from 80 nm down to 6 nm. The particles are probed simultaneously, under same conditions, during in-situ redox reaction using X-ray photoemission electron microscopy elucidating the size effect during the early stage of oxidation, yielding time-dependent evolution of iron oxides and the mechanism for the inter-conversion of oxides in nanoparticles. Fabrication of well-defined system followed by visualization and investigation of singled-out particles eliminates the ambiguities emerging from dispersed nanoparticles and reveals a significant increase in the initial rate of oxidation with decreasing size, but the reactivity per active site basis and the intrinsic chemical properties in the particles remain the same in the scale of interest. This advance of nanopatterning together with spatially-resolved single nanoparticle X-ray absorption spectroscopy will guide future discourse in understanding the impact of confinement of metal nanoparticles and pave way to solve fundamental questions in material science, chemical physics, magnetism, nanomedicine and nanocatalysis.
authors.affiliation: Laboratory for Micro and Nanotechnology, Paul Scherrer Institute, 5232 Villigen-PSI, Switzerland.|Institute for Chemical and Bioengineering, ETH Zurich, Switzerland.
authors.forename: Waiz
authors.initials: W
authors.lastname: Karim
authors.affiliation: Swiss Light Source, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland.
authors.forename: Armin
authors.initials: A
authors.lastname: Kleibert
authors.affiliation: Institute for Chemical and Bioengineering, ETH Zurich, Switzerland.
authors.forename: Urs
authors.initials: U
authors.lastname: Hartfelder
authors.affiliation: Swiss Light Source, Paul Scherrer Institut, 5232 Villigen PSI, Switzerland.
authors.forename: Ana
authors.initials: A
authors.lastname: Balan
authors.affiliation: Laboratory for Micro and Nanotechnology, Paul Scherrer Institute, 5232 Villigen-PSI, Switzerland.
authors.forename: Jens
authors.initials: J
authors.lastname: Gobrecht
authors.affiliation: Institute for Chemical and Bioengineering, ETH Zurich, Switzerland.|Laboratory for Catalysis and Sustainable Chemistry, Paul Scherrer Institute, 5232 Villigen-PSI, Switzerland.
authors.forename: Jeroen A
authors.initials: JA
authors.lastname: van Bokhoven
authors.affiliation: Laboratory for Micro and Nanotechnology, Paul Scherrer Institute, 5232 Villigen-PSI, Switzerland.
authors.forename: Yasin
authors.initials: Y
authors.lastname: Ekinci