Expanding the Repertoire of Chalcogenide Nanocrystal Networks: Ag2Se Gels and Aerogels by Cation Exchange Reactions

Cation exchange is shown to be a simple and efficient method to prepare nanostructured Ag2Se gets and aerogels from CdSe get precursors. Treatment of CdSe wet gets with AgNO3 yields, for the first time, Ag2Se gets, and these are transformed to high surface area, nanostructured aerogels by supercritical fluid drying. The striking similarity in crystallite size, morphology, and surface area characteristics between CdSe and the corresponding Ag2Se aerogels supports a mechanism in which the bonding within the get network remains globally unchanged, even as the structural attributes of the primary particle components are undergoing a dramatic transformation (hexagonal CdSe to cubic Ag2Se). Intriguingly, the rapid exchange also enables exquisite control of composition on the macroscale; reduced concentrations of Ag+ lead to two-component (i.e., CdSe inside, Ag2Se outside) heterogeneous structures of mm-cm dimensions. Overall, this methodology offers a simple approach for the generation of porous nanocrystalline metal chalcogenide networks of known or new compositions.