Noble Nanocatalysts Regulated By Bioinspired Strategies And Theirs Catalytic Activity For Aqueous Reactions

In this article, biomimetic regulation of noble metal nanocatalysts and their catalytic reduction of 4-nitrophenol by NaBH4 or hydrogenation were studied. Noble metal nanocatalysts include Pt and Pd nanoparticles regulated by biomimetic, noble-metal loaded on dopamine microspheres, SBA-15 supported noble metals regulated by dopamine, and Fe3O4 nanowire loaded noble metal (Pd and Pt).The peptides (T7 and S7), bovine serum albumin (BSA), mussel-inspired dopamine and dendritic polyamide (PAMAM) were firstly used to synthesize Pt or Pd nanoparticles. Pt nanoparticles with different morphologies were obtained by the biomimetic shape-directing agents, and their catalytic reduction of 4-nitrophenol by NaBH4 was studied. Results showed that peptide S7 for the regulation of Pt nanoparticles effectively enhanced the catalytic activity of Pt nanoparticles about 10 times compared with control Pt nanoparticles. For Pd nanoparticles regulated by S7, the catalytic activity was 50 times than control Pd nanoparticles. This shows that the specific biomimetic means s can effectively improve the catalytic propertie of nanoparticles.Furthermore, biomimetic regulation of supported noble-metal catalysts was demonstrated. First, we prepared dopamine microspheres with NaOH and dopamine. Then the microspheres were used as support to load Pt, Pd, Au or Ag nanoparticles. The as-synthesized catalysts were applied for the catalytic reduction of 4-nitrophenol by NaBH4. It was found that the catalytic activity of Au, Ag, Pt nanoparticles loaded on dopamine microspheres increased 10 times. Moreover, the catalytic activity of Pd nanoparticles loaded on dopamine microspheres raised about 49 times. In addition, the dopamine microspheres supported Pt (or Pd presented good catalytic activity for the hydrogenation of 4-nitrophenol.For dopamine regulation of noble metal nanocatalysts loaded on mesoporous SBA-15, we studied their topography and catalytic reduction of 4-nitrophenol by NaBH4 or hydrogenation. Dopamine regulated SBA-15 just by magnetic stirring, and then to load Pt and Pd nanoparticles (DA-Pt/SBA-15, DA-Pd/SBA-15). Experimental results show that DA-Pt/SBA-15 and DA-Pd/SBA-15 and has significant activity for catalytic hydrogenation at room temperature, the complete conversion time of 4-nitrophenol are 60min and 17min, respectively.In addition, water-dispersible magnetic Fe3O4 nanowire was synthesized at room temperature by coprecipitation method using bio-inspired dopamine as shape-directing surfactant. The as-synthesized nanowire was used to load noble metal (Pd and Pt) for the preparation of magnetic catalysts. The Fe3O4-nanowire supported noble metal exhibits bi-functional properties with stable water dispersion and excellent catalytic activity toward the hydrogenation of 4-nitrophenol and reduction of 4-nitrophenol by NaBH4 in water. In addition, the magnetic heterostructured nanocatalysts show good separation ability and reusability for at least 5 successive cycles without losing its catalytic activity. Moreover, the Pd/Fe3O4 nanowire can also act as an efficient catalyst for the Suzuki reaction under aqueous condition.