title: Oxidation Induced Doping of Nanoparticles Revealed by in Situ X-ray Absorption Studies.
abstract: Doping is a well-known approach to modulate the electronic and optical properties of nanoparticles (NPs). However, doping at nanoscale is still very challenging, and the reasons for that are not well understood. We studied the formation and doping process of iron and iron oxide NPs in real time by in situ synchrotron X-ray absorption spectroscopy. Our study revealed that the mass flow of the iron triggered by oxidation is responsible for the internalization of the dopant (molybdenum) adsorbed at the surface of the host iron NPs. The oxidation induced doping allows controlling the doping levels by varying the amount of dopant precursor. Our in situ studies also revealed that the dopant precursor substantially changes the reaction kinetics of formation of iron and iron oxide NPs. Thus, in the presence of dopant precursor we observed significantly faster decomposition rate of iron precursors and substantially higher stability of iron NPs against oxidation. The same doping mechanism and higher stability of host metal NPs against oxidation was observed for cobalt-based systems. Since the internalization of the adsorbed dopant at the surface of the host NPs is driven by the mass transport of the host, this mechanism can be potentially applied to introduce dopants into different oxidized forms of metal and metal alloy NPs providing the extra degree of compositional control in material design.
authors.forename: Soon Gu
authors.initials: SG
authors.lastname: Kwon
authors.affiliation: CSRRI-IIT, MRCAT, Argonne National Laboratory , Argonne, Illinois 60439 United States.|Physics Department, Advanced Materials Group, Illinois Institute of Technology , Chicago, Illinois 60616, United States.
authors.forename: Soma
authors.initials: S
authors.lastname: Chattopadhyay
authors.forename: Bonil
authors.initials: B
authors.lastname: Koo
authors.affiliation: Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA) , Dpto. de Química, FCE-UNLP, CONICET, La Plata 1900 Argentina.
authors.forename: Paula Cecilia
authors.initials: PC
authors.lastname: Dos Santos Claro
authors.affiliation: CSRRI-IIT, MRCAT, Argonne National Laboratory , Argonne, Illinois 60439 United States.|Physics Department, Advanced Materials Group, Illinois Institute of Technology , Chicago, Illinois 60616, United States.
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Shibata
authors.affiliation: Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA) , Dpto. de Química, FCE-UNLP, CONICET, La Plata 1900 Argentina.
authors.forename: Félix G
authors.initials: FG
authors.lastname: Requejo
authors.affiliation: Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA) , Dpto. de Química, FCE-UNLP, CONICET, La Plata 1900 Argentina.
authors.forename: Lisandro J
authors.initials: LJ
authors.lastname: Giovanetti
authors.forename: Yuzi
authors.initials: Y
authors.lastname: Liu
authors.forename: Christopher
authors.initials: C
authors.lastname: Johnson
authors.affiliation: Center of Advanced Radiation Sources, University of Chicago , Argonne, Illinois 60439, United States.
authors.forename: Vitali
authors.initials: V
authors.lastname: Prakapenka
authors.forename: Byeongdu
authors.initials: B
authors.lastname: Lee
authors.forename: Elena V
authors.initials: EV
authors.lastname: Shevchenko
keywords: Doping; Kirkendall effect; hollow nanoparticles; in situ studies; metal oxide