Redispersion of transition metal nanoparticle catalysts in tetraalkylphosphonium ionic liquids.

Despite the fact that particle sintering is one of the most common events leading to the deactivation of metal nanoparticle (NP) catalysts, there is a paucity of studies investigating potential routes for the regeneration of smaller, catalytically active nanoparticles from larger particles formed after repeated catalytic cycles. Here, we reveal a simple yet elegant technique for the 'redispersion' of sintered NPs in tetraalkylphosphonium halide ionic liquids (ILs). The procedure described can use environmentally benign oxidants, be carried out at mild temperatures, and is shown to be applicable to a large number of catalytically important transition metals. TEM and UV-Vis spectroscopy reveal that this methodology can indeed regenerate smaller NPs from sintered systems. A sample catalytic reaction reveals that the redispersed NPs are as catalytically active as they were prior to sintering.