Adsorbate-induced diffusion of Ag and Au atoms out of the cores of Ag@Au, AIJ@Ag, and Ag@AgI core-shell nanoparticles

摘要

Au@Ag and Ag@Au core-shell nanoparticles were synthesized using sequential laser ablation of metal targets in water. The resulting core-shell particles were then exposed to iodine or 1,6-hexanedithiol. For the Ag@Au + I-2 -> Au@Agl and Au@Ag + dithiol -> Ag@Au-dithiol reactions, inversion of the coreshell structures resulted. These findings demonstrate that adsorbates can influence the core atoms through an intervening shell, and it is possible to use core-shell systems as vehicles for delivering reactivity on demand. Changing the shell material affords an opportunity to vary core susceptibility. Au@AgI nanoparticles, for example, did not react with 1,6-hexanedithiol. These results are most consistent with a charge - transferinduced diffusion mechanism, analogous to the Cabrera-Mott model used for oxidation reactions of surfaces. The rate of uptake of iodine by Ag nanoparticles, measured with a quartz crystal microbalance, displayed kinetics that could be modeled using the same charge-transfer model.