Polymer-supported bimetallic Ag@AgAu nanocomposites: synthesis and catalytic properties.

Supported noble bimetallic nanomaterials have attracted great interest owing to their applications in catalysis. Herein, polystyrene-supported Ag@AgAu bimetallic nanocomposites were synthesized by using a seed-growth route. The size and degree of coverage of the Ag@AgAu NPs could be controlled by changing the experimental parameters. SEM, TEM, STEM, EDS, and XPS analysis was used to characterize the morphology, structure, and composition of these nanocomposites. We found that the bimetallic nanoparticles on the polystyrene beads had a core-shell structure that was comprised of a Ag core and a AgAu alloy shell. The optical properties of the nanocomposites were also studied by UV/Vis/NIR spectroscopy, which indicated that the localized surface plasmon resonance (LSPR) absorptions of the nanocomposites could be tailored over a large scale from 450 nm to 950 nm. The catalytic properties of the nanocomposites were studied by using the reduction of 4-nitrophenol (4-NP) by NaBH(4) as a model system. The results showed that the catalytic activity of the polystyrene-supported Ag@AgAu bimetallic nanocomposites was remarkably superior to that of polystyrene-supported monometallic Ag and Au nanocomposites with the same nanoparticle size. In addition, an investigation of the recycling catalytic activity of the PS-Ag@AgAu nanocomposites revealed that the catalyst possessed good stability. The enhancement of the catalytic activity was proposed to be due to the ligand and strain effects between Ag and Au.