1 research outputs found
Cu2Se and Cu Nanocrystals as Local Sources of Copper in Thermally Activated in Situ Cation Exchange
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 âacceptorâ phases represented
by rod- and wire-shaped CdSe nanocrystals. This thermal treatment slowly
transforms the initial CdSe nanocrystals into Cu2âxSe nanocrystals, through the
complete sublimation of Cd and the partial sublimation of Se atoms. Both Cu
âdonorâ and âacceptorâ 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