Study On Catalytic Properties Of Noble Metallic Nanoparticles For The Reduction Of 4-nitrophenol

In recent years, the noble metallic nanoparticles have attracted great attention because of their unusual physical and chemical properties, which makes them as suitable catalysis materials. Due to the higher surface energy, nanometer-sized metallic nanoparticles are prone to aggregate to minimize their surface area, resulting in a remarkable reduction in properties, such as loss of catalytic activity. It is necessary to immobilize metallic nanoparticles inside a carrier to prevent them from aggregation. In this thesis, three types of nano-composite microspheres have been prepared, and their properties are studied. ChapterⅠ: IntroductionThis chapter mainly reviews five types of nano-Au catalytic materials, which include the latest progress on this direction, especially for the preparative methods, catalytic performance, stab ility, recyclability. Finally, the unsolved problems and future developing prospects are also proposed. Chapter Ⅱ: Preparation of palladium/polyelectrolyte hollow nanospheres and their catalytic activity in 4-nitrophenol reductionPd/polyelectrolyte hollow nanospheres were prepared by a facile method that combined the surface- initiated atom transfer radical polymerization(SI-ATRP) and in situ growth of metal nanoparticles. TEM, FTIR, EDX and TGA were used to characterize the morphology and structure of air@PMETAI@Pd nanospheres. The result shows that Pd nanoparticles with diameter of 1.5±0.2 nm are homogeneously embedded inside the polyelectrolyte layer. Catalytic activity of the as-synthesized Pd/polyelectrolyte hollow nanospheres is investigated by using the reduction of 4-nitrophenol with Na BH4 as a model reaction. It is found that they displayed excel ent catalytic properties and good reusability. Chapter Ⅲ : Preparation of gold/hairy hollow PILs nanoparticles and their catalytic activity studyA smart hollow hybrid system was prepared by introducing poly(2-(1- methylimidazolium 3- yl)-ethyl methacrylate chloride)(PMIMC) network, the temperature responsive PDMAEMA brushes and Au nanoparticles into silica nanoparticles through two-step surface- init iated atom transfer radical polymerization(SI- ATRP) and reduction of HAuC l4. TEM, FTIR, EDX, XRD, XPS and TGA were used to characterize the morphology and structure of air@PMIMC-PDMAEMA- Au hairy hollow nanospheres. The result showed that Au nanoparticles with an average diameter of 1.5±0.2 nm were homogeneously embedded inside the PMIMC-PDMAEMA shell. Catalytic activity of the as-synthesized air@PMIMC-PDMAEMA- Au hairy hollow nanospheres were investigated by using the reduction of 4- nitrophenol with N a BH4 as a model reaction. It was found that the joint structure of PMIMC hollow nanospheres and PDMAEMA brushes lead to production of highly active and stable catalyst for reduction of 4- nitrophenol. Furthermore, the obtained air@PMIMC-PDMAEMA- Au hairy hollow nanospheres was found to have a thermally adjustable catalytic activity for the reduction of 4-nitrophenol. Chapter Ⅳ: Preparation of gold/polymer brushes and their catalytic activitywe present a very simple method to fabricate a SiO2@PNIPAM-AuNPs nanospheres. They were prepared by a facile method that combined the surface- initiated atom transfer radical polymerization(SI-ATRP) and in situ growth of metal nanoparticles. TEM, FTIR, EDX were used to characterize the morphology and structure of SiO2@PNIPAM-AuNPs nanospheres. The results showed that a small amount of Au nanoparticles with large diameter are unevenly embedded inside the PNIPAM brushes layer. Catalytic activity of the as-synthesized SiO2@PNIPAM-AuNPs nanospheres is investigated by using the reduction of 4-nitrophenol with NaBH4 as a model reaction. It is found that their catalytic performance is lower than air@PMETAI@Pd and air@PMIMC-PD MAEMA- Au.