Synthesis And Catalytic Properties Of Metal Nanoparticles With Spherical Polymer Brushes And Cyclodextrin

Metal nanoparticles exhibit different physicochemical properties as compared to their bulk materials due to their high surface-to-volume ratio,which had a broad application prospect.However,the tendency of aggregation of nanopartciles must be overcome by using capping agents and suitable carrier systems.The carrier systems played a significant role in stabilizing the metal nanoparticles and influenced their catalytic performance.Therefore,it is necessary to find the proper carrier systems of metal nanoparticles.In this thesis,spherical polyelectrolyte brushes(SPB),cyclodextrin polymer brush and cyclodextrins(CD)were chosen as carrier systems to synthesize metal nanoparticles,the properties of which were characterized by TEM.ICP-AES,Zeta potential and UV-vis spectrometer.Main work and conclusions are as follows:(1)Quenched and annealed cationic spherical polyelectrolyte brushes were prepared successfully via photo-emulsion polymerization,where gold nanoparticles(Au-NP)were obtained using in-situ reduction of chloroauric acid by sodium borohydride.The catalytic reaction of p-nitrophenol(4-NP)was used as a model reaction to testify the catalytic properties of gold nanoparticles immobilized on SPB.It was revealed that the measured rate constants(k)of the Au-NP immobilized on quenched SPB were much higher than that of Au-NP immobilized on annealed SPB.The differences of k were due to the different diffusional barriers of quenched and annealed SPB in an alkaline aqueous solution.However,the activation energy obtained by experiments of Au-NP immobilized on quenched and annealed SPB was nearly the same.(2)The CD polymer brushes were prepared by photo-polymerization using DMAEMA and CD monomer.CD monomer was synthesized by sulfonic and amination reactions.Then the gold nanoparticles with narrow size distributions were prepared in-situ reduction by CD polymer brushes without adding any reducing agent.When the gold nanoparticles were used as catalyst for the reduction of 4-NP,it was found out that the Au-NP immobilized on CD polymer brushes had a good catalytic property and the activation energy obtained by experiments of Au-NP was 30.3 KJ/mol.(3)Cyclodextrins-capped silver nanoparticles(Ag-NP)were synthesized by reducing silver nitrate with CD in an alkaline aqueous solution,which was very simple and green.The size distributions of Ag-NP prepared in certain pH and CD concentration were quite narrow.Ag-NP would aggregate in the condition of high pH(pH>12)or low CD concentration([CD]<0.025 mM).The CD-capped Ag-NP had a strong catalytic effect on the reduction of 4-nitrophenol to 4-aminophenol.It was revealed that ?-and ?-CD-capped Ag-NP had a better catalytic activity than that of a-CD-capped Ag-NP.