A Simple Method To Prepare Magnetic Noble Metal Nanoparticale Catalysts With Polypyrrole As Supports

Metal nanoparticles have drawn more and more attention due to their fantastic high catalytic activities toward different types of reactions due to their high surface area-to-volume ratio. However, there are two drawbacks that hinder their applications in real life: first, the aggregation of metal nanoparticles in solution results in remarkable reduction in their catalytic activities; second, they are difficult to be recycled from reaction solution due to small size.To sovle this two problerms, the reseachers use to a support to immobilize the metal nanoparticlesPolypyrrole(PPy)as a conducting polymer has numerous amino groups on their backbone, these amino groups can supply coordination interaction with metal salt. And the interaction is good for forming uniform distribution and small diameter nanoparticales. PPy was a good support for metal nanoparticles in sovling the aggregation of metal nanoparticles. We incorporate magnetic nanoparticles into catalytic to make it reuseable and can be easily seprated by external magnetic field.In chapter 3, we have introduced a simple way to prepare Au@PPy/Fe3O4 catalysts with Au nanoparticles embedded in PPy/Fe3O4 capsule shell. First, we Poly dimethyl diallyl ammonium chloride(PDDA) modify PS nanoparticles with positively charged surface made them favorable for electrostatic attachment with negatively charged Au nanoparticles and form PS/Au composites. Fe Cl3·6H2O was added into mixture of PS/Au composites and pyrrole monomer to initiate polymerization of pyrrole monomer. When the reaction proceeded, Fe Cl2·4H2O and NH3·H2O were added into the system successively under nitrogen protection. The PS/Au@PPy/Fe3O4 composites were prepared. Finally, to obtain Au@PPy/Fe3O4 hollow capsules, the as-prepared PS/Au@PPy/Fe3O4 composites were soaked in tetrahydrofuran solution for a night to remove PS cores.Au@PPy/Fe3O4 hollow capsules exhibited excellent catalytic activity towards the reduction of MB dye solution with Na BH4 as reducing agent.No significant decrease in catalytic activity of Au@PPy/Fe3O4 hollow capsules was detected, even after the catalytic experiments were repeated 5 times.In chapter 4, we reported a novel strategy to construct magnetic hollow capsules with Pd and Fe3O4 nanoparticles embedded in PPy shell through only two steps: first, synthesization of Pd nanoparticles, preparation of Fe3O4 nanoparticles, assembly of Pd and Fe3O4 nanoparticles, and formation of PPy shell were achieved in one-step on the surface of PS nanospheres; then, the PS core was selectively removed by THF solution. The as-prepared Pd/Fe3O4/PPy hollow capsules exhibited good catalytic property in reduction of 4-nitrophenol with Na BH4 as reducing agent. Due to incorporation of Fe3O4 nanoparticles, the catalysts could be quickly separated from the reaction solution by magnet. And also the catalytic show good reusable quality.In chapter 5, we reported a novel strategy to construct magnetic recyclable catalysts with Pd and Fe3O4 nanoparticles anchored on reduced graphene oxide(r GO) nanosheet surface and embedded in PPy shell. During the preparation, synthesization and assembly of both Pd and Fe3O4 nanoparticles, preparation of PPy layer, and reduction of graphene oxide nanosheets could be finished in one-step.In reduction of 4-nitrophenol with Na BH4 as reducing agent, their catalytic performance was better than recent reports. Moreover, the catalysts could be easily recycled from reaction solution by magnet and showed good reusability.