The Study Of Graphene Oxide And Its Composite In Surface-enhanced Raman Scattering

Surface-enhanced Raman scattering (SERS) as a kind of high sensitivity, highselectivity, mild detect condition and many other advantages test means, has beenwidely used in the fields of Surface Science, Analytical Science, Biological Scienceand so on. The morphology, dimension and type of the SERS substrates have animportant effect on the signals of adsorbed molecules. Presently, the main substratesof SERS including metal sols, metal island films, double metal nanoparticles,metal-semiconductor composite materials and so on. Some of these substrates haveshown some application potential, but there is still a distance for practical application.Graphene is a star material developing rapidly in recent years, due to its uniquephysical and chemical properties, graphene is becoming the focus in the field ofscientific research. Using graphene or its compounds as SERS substrates have beenreported in literatures. Graphene have the advantages of simple synthesis, low cost,stable properties, good biological compatibility and so on. In the thesis, we usednatural graphite powder as raw material synthesized graphite oxide with modifiedHummers method, studied graphene oxide (GO) and its compound’s SERS activity.The major contents summarize as follows:(1) Graphite oxide was synthesized from natural graphite powder with modifiedHummers method. Exfoliation of graphite oxide to GO was achieved byultrasoncation of the aqueous solution of graphite oxide. Monolayer GO presents assilk veil waves, the distance of graphite oxide layers is about0.754nm, there arehydroxyl, carbonyl, epoxy, carboxyl functional groups on the surface of GO. Thereare two models of Raman spectrum in GO, one is the first-order, another is thesecond-order. The D band which is induced by structural disorder and the G bandwhich is graphite’s intrinsic Raman model, the two bands both belong to the first-order spectrum of GO. The second-order spectrum of GO also contain two bands,one is the overtone of the D band called as D＊, another is the overtone of the G bandcalled as G＊, G＊is the same as D band which is induced by structural disorder,vanishing for completely defect-free graphite.(2) In aqueous solution synthesized Ag/graphene nanocomposite with an in situchemical synthesis approach. Graphene remain existed as single layer structure innanocomposite. Silver nanoparticles that modified on the surface of Ag/graphenenanocomposite existed as zero valence of the pure state. When GO be reduced tographene oxygen functional groups didn’t vanish, still contain carbonyl groups. Usingthe synthesized nanocomposite as SERS substrate to detect crystal violet, thenanocomposite showed stronger SERS activity as compared with pure GO and Agsol.(3) Prepared GO/R6G/Ag sandwich structure and GO/Ag/R6G similar sandwichstructure by layer-by-layer self-assembly method. From the SEM images of Ag sol,we found that most of the synthesized Ag nanoparticles were spherical, size at about70nm, there was some degree of aggregation after assembled on sandwich structure.As the concentration of R6G changed, the structure that given the strongest SERSsignal was not the same. On the one hand due to the quantity of R6G saturatedadsorption is different for GO and Ag nanoparticles. On the other hand due to theenhancement of GO belongs to chemical enhancement.