Preparation of Au/Ag Multilayers via Layer-by-Layer Self-assembly in Spherical Polyelectrolyte Brushes and Their Catalytic Activity

Spherical polyelectrolyte brushes （SPBs） consisting of polystyrene （PS） core and poly（2-aminoethyl methacrylate hydrochloride） （PAEMH） shell were prepared by photo-emulsion polymerization. Au nanoparticles （Au-NPs） with controlled size and size distribution were synthesized in situ using SPBs as nanoreactors. Via layer-by-layer deposition technique on the surface of SPBs, nano-composite particles with Au/Ag-NPs bilayer and Au/Ag/Au-NPs trilayer were prepared. The structures of the as-prepared Au/Ag multilayer SPBs were characterized by UV-Vis spectroscopy, TEM, ICP-AES and DLS. The charge reversal of the nano-composite particles observed by zeta potential confirmed the success of layer-by-layer assembly. The Au/Ag-NPs bilayer nano-composite particles showed high catalytic efficiency with an apparent activation energy of about 41.2 kJ/mol in the reduction reaction of 4-nitrophenol to 4-aminophenol in the existence of sodium borohydride monitored. The catalytic activity ofAu/Ag-NPs multilayer SPBs close to that of Au-NPs SPBs and much higher than that of Ag-NPs SPBs reveals its potential applications in cost-effective catalysts with high-performance.