In situ formation of Ag nanoparticles in spherical polyacrylic acid brushes by UV irradiation

We reported on the in situ synthesis of silver nanoparticles onto polystyrene (PS) core-poly(acrylic acid) (PAA) polyelectrolyte brush particles. The synthesis of these composite particles proceeds through a photoemulsion polymerization in aqueous dispersion using the functional monomer silver acrylate. In this way the layer of the chains of poly(acrylic acid) on the surface and the Ag nanoparticles are formed at the same time. Dynamic light-scattering (DLS) measurement demonstrates the formation of polyelectrolyte brushes onto the PS core surface. TEM and cryo-TEM images show that well-dispersed Ag nanoparticles (d = 3 +/- 1.2 nm) are formed in situ on the surface of PS-PAA spherical polyelectrolyte brush particles. Moreover, wide-angle X-ray scattering indicates that Ag nanoparticles formed in the brushes are crystalline. The catalytic activity is investigated by monitoring the reduction of 4-nitrophenol by NaBH4 in presence of these silver nanocomposite particles. The rate constant k(app) of this reaction was found to be slightly smaller than the one of Pd or Pt nanoparticles immobilized on carrier particles of the same type. All data demonstrate that the present way of synthesis leads to extremely small Ag particles immobilized on a stable carrier.