Surface Plasmon-enhanced Photocatalytic Activity Of Metal-semiconductor Hetero-nanostructure

In order to solve the increasingly serious energy crisis and environmental pollution problems,scientists around the world are continuously exploring new energy source and purification method,such as solar energy and photocatalysis.The design of new hetero-nanostructure materials with high photovoltaic conversion and excellent photocatalytic activity have been studied by lots of researchers in recent years.Due to the unique surface plasmon resonance property,metal nanoparticles have been widely used in photovoltaic device,information storage and biomedical application.With the fantastic physical consistency,metal nanoparticles also be regarded as the ideal component in hetero-nanostructures.In this paper,we have synthesized metal-semiconductor hetero-nanostructures with different morphology,component and function based on three different metal nanoparticles,and investigated their outstanding performance in photocatalytic degradation of dye,water splitting and Fenton-like reaction,the followings are the details:Firstly,we have reported a general and facile approach to synthesize uniform dumbbell-like gold-sulfide core-shell hetero-nanostructures.The transformation from Au nanorods(NRs)to dumbbell-like Au NRs and coating of metal sulfide shells(including Bi2S3,CdS,CuxS,and ZnS)were achieved in a one-pot reaction.Due to the reshaping of Au core and the deposition of sulfide shell,the plasmon resonances of Au NRs were highly enhanced,especially the about 2 times enhancement for the visible transverse plasmon resonance compared with the initial Au NRs.Owing to the highly enhanced visible light absorption and strong local electric field,we found the photocatalytic activity of dumbbell-like Au-Bi2S3 NRs was largely enhanced compared with pure Bi2S3 and normal Au-Bi2S3 NRs by testing the photo-degradation rate of Rhodamine B(RhB).Moreover,the second-layer sulfide could be coated and the double-shell Au-Bi2S3-CdS hetero-nanostructures showed further improved photo-degradation rate,especially about 2 times than that of Degussa P25 TiO2(P25)ascribing to the optimum band arrangement and then the prolonged lifetime of photo-generated carriers.Secondly,we have developed a well-controlled synthesis strategy to prepare an each-contacted Au-Pt-CdS hetero-nanostructure with Pt on the tips and CdS layer along the sides of Au nanotriangle(NT),which exhibits excellent photocatalytic activity for hydrogen production under light irradiation(?>420 nm).The sequential growth and surfactant-dependent deposition produce the three-component Au-Pt-CdS hybrids with Au NT acting as core while Pt and CdS serving as co-shell,which Au,Pt and CdS have reasonable direct contact with one another.Due to the presence of Au NT cores,the Au-Pt-CdS nanostructures possess highly enhanced light-harvesting and strong local electric field enhancement.Moreover,the intimate and multi-interface contact generates multiply electron transfer pathways(Au to CdS,CdS to Pt and Au to Pt)which guide photo-excited electrons to the co-catalyst Pt for efficient hydrogen reduction reaction.Through evaluating the hydrogen production rate when aqueous Na2S03-Na2S solution is used as sacrificial agent,the Au-Pt-CdS hybrids exhibit excellent photocatalytic activity which is about 2.5 and 1.4 times as large as that of CdS/Pt and Au@CdS/Pt,respectively.Thirdly,we have used a steerable hydrothermal method to control the growth of Ag2S shells onto Au nanotriangles(NTs)with tunable plasmon resonance and local field distribution.Through adjusting pH value and sulfur source,three types of Au/Ag2S hetero-nanostructures are obtained,including shells on the tips(Au/Ag2S(tips)),shells on the sides(Au/Ag2S(sides)),and complete shells(Au@Ag2S).The surface plasmon resonance and local field confinement are demonstrated to vary with the shell position.Furthermore,compact CdS nanoshells are coated onto the Au@Ag2S without any shape change of Au cores.By testing the photodegradation rate of Rhodamine B(RhB)under visible light irradiation,the Au@Ag2S@CdS hybrids exhibit enhanced photocatalytic activity compared with Au@CdS and CdS.The strong local electric field,the enhanced visible light absorption,and the optimum band arrangement between Ag2S and CdS are thought to be the main factors.Finally,based on Au nanospheres we synthesized two types of Au-ZnO with entirely different mopholpgy,including Au@ZnO core-shell nanostructures and Au decorated ZnO hybirds.Two types of Au-ZnO exhibits different surface plasmon resonance properties and similar photoluminescence quenching.Through introduce of H2O2,we test the Fenton-like reaction activity of Au NS,Au@ZnO and Au/ZnO under different light irradiation.For Au@ZnO hybirds,Au NSs are entirely wrapped by ZnO and it almost has no photocatalytic activity.When the incident light wavelength above 420 nm,the activity of Au/ZnO is a little lower than pure Au NSs;while the activity of Au/ZnO is obvious enhanced and exceed Au NSs when the incident light both including ultraviolet and visible light.We investigate the mechanism of this phenomen and think the band absorption of ZnO and SPR property of Au play important role.