Abstract:
Metal nanoparticles have attracted more and more attention due to their high activity and selectivity in catalytic applications recently. Spherical polyelectrolyte brushes (SPB) have been proved to be excellent carriers for the generation and immobilization of metal nanoparticles and they are stable in water due to the steric electrostatic repulsion of the polyelectrolyte brush layer. In this paper, magnetic spherical polyelectrolyte brushes (MSPB) consist of a core of polystyrene embedded with magnetite particles and a well defined shell of negatively charged poly(acrylic acid)s (PAA) brush. Silver nanoparticles were synthesized with MSPB as a carrier by reduction of Ag
+ in the brush layer in presence of BH
4− and characterized by dynamic light scattering (DLS), transmission electron microscope (TEM), thermal gravimetric analysis (TGA), and ultraviolet spectrophotometer (UV). The reduction of 4-nitrophenol was used as a benchmark reaction to investigate the catalytic ability and recyclability of silver nanoparticles. TEM images showed that magnetite particles were successfully embedded into the PS cores and Ag nanoparticles with diameter of 2.30 nm were immobilized in the MSPB. The prepared MSPB was narrowly dispersed, stable, pH sensitive, rapidly responsive to magnetic fields, and redispersible. The obtained MSPB-Ag composites were also narrowly dispersed and separated rapidly by external magnetic fields. High catalytic activity was found in the reduction of 4-nitrophenol by NaBH
4 in the presence of MSPB-Ag composites. The activation energy of MSPB-Ag composites in the reaction was calculated to be 66.03 kJ/mol, which was approximate to the SPB-Ag composites. This proposed approach opens a new way for the preparation of recyclable metal nanocatalysts with high activity.