Preparation Of Array Assembly Of Au And Ag Nanoparticles And Study On Sers And Surface Catalytic Reactions

Noble metal nanostructured surface plasmon(SP)have been widely used in photovoltaics,photoelectric detection,surface-enhanced Raman scattering,and photocatalysis due to their optical properties such as breaking optical diffraction limits,high locality,and near field enhancement.The morphology,size,surface defects,dielectric properties,and arrangement of nanoparticles have a great impact on their physical properties.Ag nanoparticles have excellent SERS activity and photocatalytic performance,but their weak chemical stability in an oxidizing environment makes it difficult to preserve and prevents the full play of their optical properties.For this reason,many researches have focused on Au-Ag alloy nanoparticles.While effectively reducing the effect of oxidation on its optical properties,the properties of two different metals are concentrated on a single nano-particle,which further expands its field of SERS and photocatalysis range of applications.In addition,the uniformity of the SERS substrate is also one of the important indexes affecting the detection performance of the SERS.Therefore,studying how to prepare nanoparticles substrate with good dispersibility and improving substrate uniformity is a key research topic in the field of SERS substrate preparation and photocatalysis,and has important application research value.In this thesis,by exploring the preparation of uniform array of Au and Ag bimetallic nanoparticles and graphene composite substrate,the application of the substrate in the realization of SERS and surface plasmonic catalysis is explored.Two methods are proposed in this paper to prepare SERS substrate.The first method is to use a liquid interface self-assembly method and a protection-etching method to prepare a “sandwich” configuration Au-Ag alloy nanoparticles/graphene/Au-Ag alloy nanoparticles composite array substrate.The effects of the size of metal nanoparticles and the number of substrate layers on the SERS activity of the substrate were investigated.The second method is to use an evaporation self-assembly method to prepare Au-Ag core-shell nanorods horizontal array,and the micromorphology of the self-assembly array was adjusted by changing the molecular concentration of cetyltrimethylammonium bromide(CTAB).The SERS spectrum of the molecules on the surface of the substrate is monitored in real time using the SERS system to achieve in situ monitoring of the surface plasmonic catalysis process and analyze the catalytic mechanism.The main research contents are as follows:1.Au-Ag alloy nanoparticles were prepared by wet chemical method.On this basis,with the help of self-assembly methods and the introduction of single-layer graphene,a single layer(Au-Ag alloy nanoparticles single-layer structure),double-layer(Au-Ag alloy nanoparticles/graphene composite structure),and three-layer(Au-Ag alloy nanoparticles/graphene/Au-Ag alloy nanoparticles composite structure)substrate were prepared on silicon wafers.Rhodamine 6G(Rh6G)was selected as a probe molecule in the experiment to study the regulation of nanometer particle size,alloy ratio and layer number on the substrate SERS effect.The results showed that the SERS activity of the substrate strongly depends on the alloy particle type,size,and number of layers.And it was found that the Raman signal enhancement of Rh6 G molecule mainly originates from the charge transfer between metal and graphene.The relevant research conclusions indicate the potential application value of the prepared substrate in the fields of sensing,photoelectric detection and other fields.2.Firstly,Au nanorods were prepared by wet chemical method.Based on this,Au-Ag core-shell nanorods were synthesized by in situ growth method.Subsequently,an evaporation self-assembly method was used to prepare an ordered array of Au-Ag core-shell nanorods array on a silicon wafer;in the experiment,4-nitrothiophenol(4NTP)was selected as the probe molecule,and the Raman spectrum of the probe molecule on the substrate surface was observed to realize the in situ monitoring of the plasmonic catalytic reaction process on the substrate surface.The study found that the existence of the Ag shell layer in the Au-Ag core-shell nanorods contributed significantly to the substrate's catalytic performance,which provided a possible way to prepare highly efficient photocatalytic substrates.3.The Au-Ag core-shell nanorods horizontal array substrate was prepared by evaporation self-assembly method,4NTP and 4-aminothiophenol(4ATP)were selected as probe molecules.The surface catalytic reaction of the substrate was monitored in situ by means of a micro-confocal Raman spectrometer,and the influence of the excitation light power on the molecular catalytic reaction was studied.Experiments have found that increasing the power of the excitation light can accelerate the progress of the catalytic reaction.In addition,Au-Ag core-shell nanorods horizontal array/single-layer graphene composite substrate was prepared by a protection-etching method,and 4NTP was selected as the probe molecule.Substrate surface catalytic reaction in situ monitoring of by micro-confocal Raman spectrometer.The results showed that single-layer graphene can promote the charge transfer between the substrate and the probe molecules,and effectively improve the catalytic reaction efficiency of the substrate.