Dendronized Chitosan-Mediated Fabrication of Au@AgNPs with Visible Light Trigger

Fabrication of alloy metal nanoparticles with controllable size, morphology, and different compositions under environmentally benign and sustainable conditions is important for their versatile applications. Here, we report on a route for the visible-light-triggered fabrication of monodispersed gold and silver alloy nanoparticles (Au@AgNPs) in aqueous conditions through the confinement of dendronized chitosans (DCSs). These DCSs carry densely packed threefold dendritic oligoethylene glycol (OEG) pendants, which integrate the features of water solubility and biocompatibility from chitosan, as well as thermoresponsiveness, crowded structures, and multivalency from dendronized topologies. These DCSs provide structure-dependent confined microenvironments on the molecular level to complex with metal ions and mediate their conversion into Au@AgNPs upon irradiation with visible light without any external chemical reducer. Au@AgNPs with different Au and Ag compositions are embedded within the DCSs to form stable nanocomposites, which show promising photothermal properties. In addition, these nanocomposites exhibit excellent catalytic activity in the reduction of 4-nitrophenol.