The Controlled Growth Of Noble Metal Nanoparticles On The Surface Of Functional Colloid Particles

Noble metal nanoparticles have aroused great interest due to their unique photoelectric and catalytic properties,low toxicity and good stability.Specifically,when combined with superparamagnetic properties of magnetic nanoparticles,the resulted metal magnetic hybrids can exhibit extraordinary properties,which demonstrate significant potentials in biomedical engineering,environmental governance and especially in catalysis for their unique magnetic responsiveness.In order to achieve the aforementioned hybrids with multifunctionality,it is urgently needed to develop a facile and robust approach to construct wel-controlled multifunctional magnetic particles hybrids that decorated with noble metal nanoparticles,allowing potential applications in catalytic system.The research contents are as follows:（1）Preparation of Fe₃O₄@SiO₂-SH/Pd and Fe₃O₄@SiO₂-SO3H/Pd composite microspheres and researches their catalytic activity: Core-shell Fe₃O₄@SiO₂-SH spheres are synthesized through one-step deposition of 3-（mercaptopropyl）trimethoxysilane on the surface of Fe₃O₄ spheres,which can be further employed as a carrier to receive Pd nanoparticles for Fe₃O₄@SiO₂-SH/Pd composite spheres via covalent bonding interactions between –SH and Pd.Additionally,when exposed to H2O₂,the Fe₃O₄@SiO₂-SH spheres can also experience an oxidization process to form Fe₃O₄@SiO₂-SO3 H spheres.Owing to the strong electrostatic interaction between Pd2+ and –SO3H,Pd2+ is easily attached onto the surface of the spheres.Followed by an in-situ reduction of NaBH4,Fe₃O₄@SiO₂-SO3H/Pd composite spheres can be successfully obtained.Both of the Fe₃O₄@SiO₂-SH/Pd and Fe₃O₄@SiO₂-SO3H/Pd catalysts exhibit good catalytic and recycle performances in the reduction of 4-nitroaniline.The results demonstrate that the Fe₃O₄@SiO₂-SO3H/Pd system behaves better catalytic activity than that of Fe₃O₄@SiO₂-SH/Pd.More importantly,when experiences 14 successive cycles,the percent conversion of 4-nitroaniline still maintains more than 90%.（2）Fabrication of Fe₃O₄@SiO₂-SO3H@PPy-Pd composite microspheres and their application in recyclable catalysts: The as-prepared Fe₃O₄@SiO₂-SO3 H spheres are used as a carrier to receive Pd2+ via electrostatic attraction between-SO3 H species and Pd2+ ions.The Pd2+ can be further employed as an oxidant to induce polymerization among pyrrole monomers,resulting PPy-Pd hybrids attached onto the Fe₃O₄@SiO₂-SO3 H spheres.It is a facile and high-efficient strategy for fabricating magnetic conductive polymer-noble metal composites,which can act as efficient catalysts in reduction of 4-nitrophenol and Suzuki coupling reaction due to their high activity,ease of separation,and excellent reusability.（3）Synthesis of Fe₃O₄@SiO₂-NH2@PDMAEMA@Au composite microspheres and their application as thermally adjustable catalysts: Fe₃O₄@SiO₂ spheres are synthesized by the sol–gel method with tetraethoxysilane（TEOS）,followed by an introduction of the the photoactive amino group onto Fe₃O₄@SiO₂ NPs via chemical bonding of（3-aminopropyl）triethoxysilane（APTES）.Through a self-initiated photografting and photopolymerization（SIPGP）strategy,poly（2-（dimethylamino）ethyl methacrylate）（PDMAEMA）brushes can be successfully grafted onto the surface of Fe₃O₄@SiO₂-NH2.Due to the strong electrostatic interaction between C-N+ species of the PDMAEMA chains and AuCl4–,AuCl4-can be uniformly attached onto the PDMAEMA brushes.When exposed to the NaBH4,AuCl4– can be further reduced to Au nanoparticles,resulting in the formation of Fe₃O₄@SiO₂-NH2@PDMAEMA@Au nanocomposites.Owing to the stimuli-responsive properties of PDMAEMA brushes,the as-prepared nanocomposites demonstrate thermally adjustable catalytic properties and excellent recycle performances in the reduction of 4-nitrophenol reaction.