Abstract: Magnetic supports were prepared by coating Fe₃O₄ nanoparticles with polystyrene (PS). The target nanocomposites were formed by growing polyamidoamine (PAMAM) dendrimers on the magnetic polymer supports with carboxylic groups and then silver nanoparticles were embedded into the PAMAM dendrimer shell. In this way recoverable Fe₃O₄@PS@PAMAM-Ag nanocomposites were successfully prepared. The magnetic nanocatalysts were characterized by Fourier transform infrared spectra, scanning electron microscopy,?inductively coupled plasma, and X-ray photoelectron spectroscopy. The results demonstrated that the PAMAM dendrimer shell immobilized on the magnetic supports was beneficial for dispersion and stabilization of the silver nanoparticles. The silver content of the Fe₃O₄@PS@PAMAM(G7)-Ag nanoparticles was 1.64 wt%. The catalytic activity of the Fe₃O₄@PS@PAMAM-Ag nanocomposites was proved using the reduction of 4-nitrophenol as a model catalytic reaction. The nanocomposites could be readily separated by magnetic separation and reused for the next reduction with high efficiency. The catalytic activity remained completely even after the nanocatalyst had been recycled six times.

Key words: magnetism, recoverable catalysis, polyamidoamine dendrimer, silver, p-nitrophenol