Nanowire-film Assisted Surface Enhanced Raman Scattering And Plasmon Driven Surface Catalyzed Reaction

The nanoscale metal materials have significant application prospect in ultrasensitive sensor detection,new energy,new functional structure and information storage owing to their unique physical and chemical properties.So limiting the size of the material in the nanoscale range to study the interaction of light with matter is an important research field of nanometer materials.Surface Plasmon refers to the free electrons collective oscillation at interface of metal and medium excited by electromagnetic field.This oscillation elementary excitation can be regarded as quantization of quasiparticle,which has a lot of novel optical properties.With the rapid development of nanotechnology and the improvement in surface palsmon application research,plasmonnics comes out as a new subject and develops rapidly,which has wide application prospect in the field of physics,chemistry,materials,energy.With the restrictions on the size of structure,free electrons in the metal nanoparticle excited by electromagnetic field can only do the collective oscillation at nanoparticle surface that is called localized surface plasmons(LSPs).This kind of surface plasmon resonance can lead to electromagnetic field redistribution in the nanostructure and great enhancement in electromagnetic field intensity,which has been widely used in enhanced spectrum,high sensitive molecular signal detection,etc.Surface enhanced Raman scattering(SERS)is based on metal nanostructures electromagnetic field enhancement effect,which is used to strengthen the weak Raman scattering signals,enhance efficiency can reach 104-106 and even higher.Information about material chemical structure,composition and phase morphology can be obtained from the Raman scattering signal,which also use molecular characteristic peak to reflect the catalytic reaction occurs or not.The Raman and electromagnetic field enhancement in nanostructure are closely related to nanomaterial type,structure characteristics,geometric shape,and size and so on.In this paper,based on the metal nanowires-film hybrid system,PATP or 4NBT molecules are used as probe molecules to study the influence of substrate material,excitation light polarization direction,coupling efficiency and structural symmetry broken on surface enhanced Raman scattering and plasmon driven surface catalytic reaction.The experimental and simulation results all show that metal film has better effect of electromagnetic field enhancement and Raman enhancement than dielectric film due to stronger coupling effect between free charge on nanostructure surface and image charge on metal film.Different surface plasmon models were excited under different polarized exciting light,which resulting in the polarization dependence of Raman and electromagnetic field enhancement.Structural symmetry broken can improve the excitation and coupling efficiency of plasmon with better electric field enhancement and Raman enhancement effect.For instance,the terminal of nanowire has better effect of electric field enhancement and Raman enhancement than middle because of higher coupling efficiency arising from structural symmetry broken.Structural symmetry is broken when a nanoparticle adjacent to the nanowires.This asymmetric structure will greatly improve the effect of Raman enhancement and the ability of driving the catalytic reaction.