A new type of raspberry-like polymer composite sub-microspheres with tunable gold nanoparticles coverage and their enhanced catalytic properties

A new type of gold nanoparticles-coated composite spheres with chemically reactive poly(glycidyl methacrylate) colloids as cores is synthesized in raspberry-like fashion via a controlled assembly method. The surface coverage of the immobilized gold nanoparticles, which is controlled by the surface charge density of the poly(allylamine hydrochloride)-modified polymer spheres and the conformation of the adsorbed polyelectrolyte chains on the spheres, can be tuned with polyelectrolyte concentration, ratio of polymer spheres to gold nanoparticles, and the pH value of the solution. A double-conformation poly(allylamine hydrochloride) film structure: inner collapsed and outer extended, is proposed to explain how the polyelectrolyte concentration, ratio of polymer spheres to gold nanoparticles, and the pH value of the solution affect the adsorption amount of the gold nanoparticles on the modified polymer spheres. The obtained composite particles are stable without loss of the gold nanoparticle coatings even after applying ultrasonication, cleaning or long term nanopure water storage. These composites exhibit an excellent catalytic activity with an average turnover frequency of 250.5 mol mol−1 s−1 and the fastest reported reduction of 4-nitrophenol with sodium borohydride is achieved within 76 s.