Expanding the Repertoire of Chalcogenide Nanocrystal Networks: Ag_2Se Gels and Aerogels by Cation Exchange Reactions

摘要

An aerogel is a unique class of material consisting of a highly porous network composed of connected nanoscale building blocks. The presence of an interconnected network of pores, including both micropores (<2 nm) and mesopores (2-50 nm), with a high inner surface area nanostructure is expected to lead to many actual and potential applications in catalysis, solar cells, and sensors. However, conventional aerogels are based on oxides and traditionally focused on insulating or wide band gap materials, such as SiO_2, TiO_2, and Al_2O_3. Recently, the aerogel family has been extended to semiconducting metal chalcogenide aerogels (PbS, CdSe, CdS, ZnS), enabling band gap tuning through the visible region. The aerogels are prepared by partial oxidative removal of thiolate capping groups from the corresponding metal chalcogenide nano-particle surface to form a wet gel, followed by supercritical solvent extraction. The obtained aerogels retain the inherent nanoparticle properties: specifically, quantum confinement effects, average pore sizes in the mesoporous regime, and very high surface areas. Among these aerogels, the synthesis of CdSe aerogels is the best developed and has been optimized to yield robust monoliths.