Study On Small Molecules Assisted Control Of Noble Metal Nanocrystals With Different Structures

Noble metal nanocrystals have been widely used in many fields because of their excellent catalytic, electrical and optical properties.Owing to their size, morphology and microstructure dependent properties ,the controlled synthesis of noble metal nanocrystals is very important and is the hot research topic in these years. There are many interactions between functional small molecules (including metal ions), metals, and the reaction media, such as coordination, adsorption and polarization,which make them have the ability to adjust the nucleation and growth of metal nanocrystals. Therefore, using small molecules to control the morphology of noble metal nanocrystals has become a hot research topic in recent years. In this thesis, we selected some small molecules, such as acetonitrile, 1,4-dioxane, methylamine and so on, to control the structure of Au, Pt and Pt-Cu nanocrystals, and evaluated the catalytic properties of the products:(1) Tanking use of the interactions between acetonitrile, 1,4-dioxane and halide ions to effectively reduce the corrosion strength of halide ions/O2 to the twin crystal structure, I have been successfully synthesized truncated icosahedra (twin crystal) nanocrystals. Further, combined the protective effect of acetonitrile with selective adsorption and coordination capabilities of methylamine, concave cubic Pt nanocrystals with high index facets were synthesized, which have higher electrocatalytic activity than that of commercial Pt/C toward methanol oxidation.(2) On the basis of the above experiment results, using the multiple interactions between acetonitrile, methylamine, metal ions, metal, and the reaction medium, I have been successfully selectively synthesized porous concave polyhedra and porous concave octahedra of Pt-Cu alloys nanocrystals with a one-pot method. Owing to their special structure, the specific catalytic activity of the two kinds of nanocrystals toward the electrocatalytic oxidation of methanol was higher than that of commercial Pt/C, and the activity of the porous concave octahedra was higher than the other one.(3) Using Cu2+, PtCl62- and PdCl42- to replace the Ag+ added in the traditional seed growth method for the synthesis of gold nanorods, and by adjusting the concentration of Cu2+, PtCI62- and so on, the effect of metal ions on the growth of gold nanocrystals was studied. The results show that the influence of Cu2+ and PtCl62- can lead to the formation of spherical Cu/Au and polyhedral Pt/Au nanoparticles, which is different from the effect of Ag+.