Construction Of Au@ZnO Core-shell Nanostructures With Photocatalytic Properties

In this paper,Au@ZnO core-shell photocatalysts were prepared by constructing(noble metal)@semiconductor core-shell nanostructures with the excellent performance.Combined with the surface plasmon resonance effect of Au nanoparticles can improve the absorption of visible light,to modify the semiconductor ZnO and study the optical response and photocatalytic performance of composite catalyst.The Au@ZnO/Pd composed of Au and ZnO as well as Pd with different loading were synthesized,to effectively enhance the interfacial charge transfer and hinder the charge recombination.The main content are as follows:1.The monodispersed and diameter of about 55 nm Au nanospheres(AuNS)were prepared by a seeds method.And then Au@ZnO core-shell nanostructures were prepared by ascorbic acid(AA)induced deposition of heterogeneous nucleation and growth process on AuNS uniform coating ZnO shell.The as-prepared of Au@ZnO core-shell nanospheres showed a strong visible absorption properties,which is ascribed to that AuNS has a strong surface plasma resonance absorption,and absorption peaks about in 550 nm.The results shows that Au@ZnO core-shell has a higher photocatalytic activity than pure ZnO nanoparticles,AuNS and other samples which were prepared under same conditions during photocatalytic degradation of organic dye rhodamine B under simulated sunlight irradiation.In addition,we choose three different wavelengths(365 nm,520 nm,660 nm)LED light to photocatalytic tests,and results show that the Au@ZnO also has the photocatalytic effect under three different wavelengths LED light.These results indicate that the photocatalytic activities of Au@ZnO core-shell nano spheres are derived from the simultaneous existence of the semiconductor optical excitation of ZnO and the hot electrons produced by surface plasmon resonance of AuNS,and the structure of composite structure greatly expanded the scope of light absorption of photocatalyst,and accelerated the separation of the photogenerated electrons and holes.Besides,as an optical electrode material,Au@ZnO core-shell nanosphere presents higher photocurrent density than pured ZnO nanoparticles under visible light irradiation.The Electrochemical impedance spectroscopy Nyquist diagram demonstrates Au@ZnO core-shell nanostructures have a higher rate of charge transfer,and further verifies the light response mechanism which we have put forward2.Au@ZnO/Pd nanocomposite photocatalysts with different content of Pd were successfully prepared by a simple photodeposition method.The as-synthesized Au@ZnO/Pd samples were characterized with XRD,SEM,TEM,STEM,etc,and the results indicated that the morphology and structure of composites are compose of three different components,including AuNS core,ZnO shell and Pd nanoparticles with loading in the surface of catalysts.The photocatalytic performance of the photocatalysts were evaluated by catalytic degradation methylene blue dye and phenol solution under simulated sunlight.The results show that Au@ZnO/Pd enhanced photocatalytic activity under simulated sunlight irradiation,and Au@ZnO/Pd2 exhibits the highest photocatalytic activity.The photoluminescence spectra and fluorescence lifetime analysis comfirm more excellent charge transfer and separation efficiency of Au@ZnO/Pd nonocomposite photocatalysts,which is ascribed to the surface plasmon resonance effect of AuNSs can improve the absorption of visible light and expand optical response of the ZnO.Pd nanoparticles can be as active electron trap,to promote the separation of photo-induced charges.