Wanchun Guo

Facile Hydrogen-Bond-Assisted Polymerization and Immobilization Method to Synthesize Hierarchical Fe3O4@Poly(4-vinylpyridine-co-divinylbenzene)@Au Nanostructures and Their Catalytic Applications

Hierarchical Fe3O4@poly(4-vinylpyridine-co-divinylbenzene)@Au (Fe3O4@P(4-VP-DVB)@Au) nanostructures were fabricated successfully by means of a facile two-step synthesis process. In this study, well-defined core-shell Fe3O4@P(4-VP-DVB) microspheres were first prepared with a simple polymerization method, in which 4-VP was easily polymerized on the surface of Fe3O4 nanoparticles by means of strong hydrogen-bond interactions between -COOH groups on poly(acrylic acid)-modified Fe3O4 nanoparticles and a 4-VP monomer. HAuCl4 was adsorbed on the chains of a P(4-VP) shell and then reduced to Au nanoparticles by NaBH4, which were embedded into the P(4-VP) shell of the composite microspheres to finally form the Fe3O4@P(4-VP-DVB)@Au nanostructures. The obtained Fe3O4@P(4-VP-DVB)@Au catalysts with different Au loadings were applied in the reduction of 4-nitrophenol (4-NP) and exhibited excellent catalytic activity (up to 3025 h(-1) of turnover frequency), facile magnetic separation (up to 31.9 emu g(-1) of specific saturation magnetization), and good durability (over 98 % of conversion of 4-NP after ten runs of recyclable catalysis and almost negligible leaching of Au).

Synthesis of hierarchical Polystyrene/Polyaniline@Au nanostructures of different surface states and studies of their catalytic properties

We synthesized hierarchical Polystyrene/Polyaniline@Au (PS/PANI@Au) catalysts through a seeded swelling polymerization and in-situ reduction procedure. PS/PANI@Au catalysts possess a core of PS as seed and template, a PANI shell with fibers and uniform gold nanoparticles on the surface. The configuration changes of the PANI chains resulting from the doping/dedoping procedure led to various loading amounts of Au nanoparticles. Reduction of 4-nitrophenol was chosen as the probe reaction to evaluate the catalytic activity of supported Au nanocatalysts. The catalytic results indicated that dedoping treatment of the PS/PANI supports provides stronger coordinative ability to metal nanoparticles as well as more -N= groups, which results in a better catalytic performance towards the reduction of 4-nitrophenol.

Fabrication of Hierarchical Fe3O4@SiO2@P(4VP-DVB)@Au Nanostructures and Their Enhanced Catalytic Properties†

Hierarchical Fe3O4@SiO2@P(4VP-DVB)@Au nanostructures were prepared in which the slightly cross-linked, thin poly(4-vinylpyridine-co-divinylbenzene) (P(4VP-DVB)) shells were constructed onto Fe3O4@SiO2 nanospheres, followed by in situ embedding of gold nanocrystals homogeneously into the P4VP chains. These slightly cross-linked chains, easily swollen by the reactants, make the gold nanocrystals accessible to the reactants, and the thin shell (about 15 nm) reduces the diffusion distance of the reactants to the active gold nanocrystals (about 5 nm), thereby enhancing their catalytic activity and utility. At the same time, confinement of gold nanocrystals within the P4VP shells prevents their migration and coagulation during catalytic transformations. Hence the nanocomposites exhibit high activity (up to 4369.5 h(-1) of turnover frequency (TOF)) and controllable magnetic recyclability without any significant loss of gold species after ten runs of catalysis in the reduction of 4-nitrophenol.