Manipulating core-shell reactivities for processing nanoparticle sizes and shapes

This paper describes new findings of an investigation of thermally-activated core-shell reactivities of nanoparticles in solutions for processing size, shape and surface properties. Gold nanoparticles of ≃ 2 nm core sizes with thiolate monolayer encapsulation were chosen as a model system for the manipulation of reaction parameters, including annealing effect, core composition and shell structure. It is revealed that, upon an evolution of particle sizes, annealing treatment of the solution in the presence of encapsulating thiols can lead to the formation of highly monodispersed nanoparticles. New insights into shell desorption, core coalescence and shell re-encapsulation have been provided by dependencies of the evolution temperature on the capping thiolate chain length and the core alloy composition. Transmission electron microscopic, FTIR and UV-Visible techniques were used to characterize the morphological and chemical properties. The implication of the results for the development of abilities in chemical processing core-shell nanoparticles is discussed.