SERS Investigation And Application Of Au@Pt Nanoparticle Monolayer Film

Surface enhanced Raman spectroscopy (SERS) is one of the most sensitive detectingtechniques which attracts a lot of attention. Fabrication of substrates is always an importantstudy in the region of SERS. Till now, the generality and reproducibility of most substratesis still not good enough, limiting the breadth of practical applications of SERS. In recentyears, novel core-shell nanostructures are well investigated. Their specific structuressupply high efficient SERS substrates. This thesis focused on preparation, assembly andapplications of Au@Pt nanoparticles. They were prepared based on the SERS-active Au asthe core and applicable Pt as the shell and assembled at the water/hexane interface to formnanoparticle monolayer film. Experiments of methanol oxidation were performed toestimate its catalytic properties. It was also employed as a SERS substrate to investigatethe the catalytic process and mechanisms at the molecular level. The main achievementswere listed as follows:(1) The pinhole free Au@Pt nanoparticles were prepared by seed-growth method andthen self-assembed into the Au@Pt monolayer film at the water/hexane interface withassistants. The optimized self-assembed conditions and the formation mechanisms of filmwere investigated in order to obtain a compact nanoparticle film.(2) The technique of transferring the monolayer films onto a Si wafer was developed.As a substrate, the monolayer film was investigated to estimate its uniformity. The resultsshowed that the nanoparticles arranged densely, resulting in the uniform signals fromdifferent areas. More than90%points located in area of±10%signal deviation, whichindicated the film can be used as an ideal SERS substrate. Besides, the transfer of sencondlayer was also successfully achieved, foming the double-layer nanoparticle substrate. Thissubstrate exhibited high SERS enhancement due to the nanoparticle coupling effects.(3) The Au@Pt film electrode was fabricated by transferring Au@Pt nanoparticlesnoto the surfaces of conductive substrates. The as-prepared film electrode exhibited great electro-catalytic activity for methanol oxidation as well as high availability. The oxidationprocess of methanol was investigated at the molecular level based on the strong enhancedeffects of Au core. The potential region of adsorbed CO was disclosed, supplying the basison resolving the mechanisms.(4) By the enhancement of Au core, the adsorption and reaction of some species,which had weak interaction with the substrate, can also be studied. The information ofadsorbed water and hydrogen on Pt was obtained through SERS spectra. It was suggestedthat hydrogen is directly adsorbed on the Pt surface as the first layer, while the waterserved as the second layer in the system.