title: Cu₂Se and Cu Nanocrystals as Local Sources of Copper in Thermally Activated In Situ Cation Exchange.
abstract: Among the different synthesis approaches to colloidal nanocrystals, a recently developed toolkit is represented by cation exchange reactions, where the use of template nanocrystals gives access to materials that would be hardly attainable via direct synthesis. Besides, postsynthetic treatments, such as thermally activated solid-state reactions, represent a further flourishing route to promote finely controlled cation exchange. Here, we report that, upon in situ heating in a transmission electron microscope, Cu2Se or Cu nanocrystals deposited on an amorphous solid substrate undergo partial loss of Cu atoms, which are then engaged in local cation exchange reactions with Cu "acceptor" phases represented by rod- and wire-shaped CdSe nanocrystals. This thermal treatment slowly transforms the initial CdSe nanocrystals into Cu(2-x)Se nanocrystals, through the complete sublimation of Cd and the partial sublimation of Se atoms. Both Cu "donor" and "acceptor" particles were not always in direct contact with each other; hence, the gradual transfer of Cu species from Cu2Se or metallic Cu to CdSe nanocrystals was mediated by the substrate and depended on the distance between the donor and acceptor nanostructures. Differently from what happens in the comparably faster cation exchange reactions performed in liquid solution, this study shows that slow cation exchange reactions can be performed at the solid state and helps to shed light on the intermediate steps involved in such reactions.
authors.affiliation: Department of Nanochemistry, Istituto Italiano di Tecnologia , Via Morego 30, 16163 Genova, Italy.
authors.forename: Alberto
authors.initials: A
authors.lastname: Casu
authors.affiliation: Department of Nanochemistry, Istituto Italiano di Tecnologia , Via Morego 30, 16163 Genova, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Genovese
authors.affiliation: Department of Nanochemistry, Istituto Italiano di Tecnologia , Via Morego 30, 16163 Genova, Italy.
authors.forename: Liberato
authors.initials: L
authors.lastname: Manna
authors.affiliation: Gatan, Inc. , 5794 W Las Positas Boulevard, Pleasanton, California 94588, United States.
authors.forename: Paolo
authors.initials: P
authors.lastname: Longo
authors.affiliation: Department of Nanochemistry, Istituto Italiano di Tecnologia , Via Morego 30, 16163 Genova, Italy.
authors.forename: Joka
authors.initials: J
authors.lastname: Buha
authors.affiliation: Department of Materials Science and Engineering, McMaster University , Hamilton, Ontario L8S 4L8, Canada.
authors.forename: Gianluigi A
authors.initials: GA
authors.lastname: Botton
authors.affiliation: Department of Materials Science and Engineering, McMaster University , Hamilton, Ontario L8S 4L8, Canada.|FEI Electron Optics , Achtseweg Noord 5, Eindhoven 5600 KA, The Netherlands.
authors.forename: Sorin
authors.initials: S
authors.lastname: Lazar
authors.forename: Mousumi Upadhyay
authors.initials: MU
authors.lastname: Kahaly
authors.forename: Udo
authors.initials: U
authors.lastname: Schwingenschloegl
authors.affiliation: Department of Nanochemistry, Istituto Italiano di Tecnologia , Via Morego 30, 16163 Genova, Italy.
authors.forename: Mirko
authors.initials: M
authors.lastname: Prato
authors.affiliation: Department of Nanochemistry, Istituto Italiano di Tecnologia , Via Morego 30, 16163 Genova, Italy.|Chemistry Division, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States.
authors.forename: Hongbo
authors.initials: H
authors.lastname: Li
authors.affiliation: Department of Nanochemistry, Istituto Italiano di Tecnologia , Via Morego 30, 16163 Genova, Italy.
authors.forename: Sandeep
authors.initials: S
authors.lastname: Ghosh
authors.affiliation: Department of Nanochemistry, Istituto Italiano di Tecnologia , Via Morego 30, 16163 Genova, Italy.
authors.forename: Francisco
authors.initials: F
authors.lastname: Palazon
authors.affiliation: Department of Nanochemistry, Istituto Italiano di Tecnologia , Via Morego 30, 16163 Genova, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: De Donato
authors.forename: Sergio Lentijo
authors.initials: SL
authors.lastname: Mozo
authors.forename: Efisio
authors.initials: E
authors.lastname: Zuddas
authors.forename: Andrea
authors.initials: A
authors.lastname: Falqui
keywords: cation exchange; electron energy loss spectroscopy; energy-dispersive X-ray spectroscopy; energy-filtered transmission electron microscopy; in situ transmission electron microscopy; scanning transmission electron microscopy
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