Preparation and plasmonic properties of polymer-based composites containing Ag-Au alloy nanoparticles produced by vapor phase co-deposition

Nanocomposite (NC) thin films with noble metal nanoparticles (NPs) embedded in a dielectric material show very attractive plasmonic properties due to dielectric and quantum confinement effects. For single component NPs, the plasmon resonance frequency can only be tuned in a narrow range. Much interest aroused in bimetallic NPs, however, many wet chemical approaches often lead to core shell particles, which exhibit multiple plasmon resonances or do not allow large variation of the NPs alloy composition and filling factor. Here, we report a vapor phase co-deposition method to produce polymer-metal NCs with embedded homogeneous Ag-Au alloy particles showing a single plasmon resonance. The method allows production of NPs with controlled alloy composition (x), metal filling (f), and nanostructure in a protecting Teflon AF matrix. The nanostructure size and shape were characterized by transmission electron microscope. Energy dispersive X-ray spectroscopy was used to determine x and f. The optical properties and the position of surface plasmon resonance were studied by UV-Vis spectroscopy. The plasmon resonance can be tuned over a large range of the visible spectrum associated with the change in x, f, and nanostructure. Changes upon annealing at 200 A degrees C are also reported.