Ionic Liquids-assisted Synthesis Of Noble Metal Nanomaterials

Nanomaterials were the base of the application of nanotechnology. The synthesis of noble metal nanostructured materials especially Au, Ag nanoparticles with controllable size and morphology was always attractive in the field of nanomaterials. As a "green" chemical product, ionic liquids (ILs) have currently attracted significant attention. Recently, the preparation of nanomaterials with the assistance of ILs was reported in the literature. The lower interface tensions and supramolecular self-assembly of ILs provide new methods for the synthesis of nanomaterials. In this dissertation, we prepared silver nanorods through ethylene glycol (EG) reduction in the presence of imidazole-based ionic liquid (IL) and polyvinyl pyrrolidone (PVP). In addition, with the assistance of short-chain and long-chain ILs, the flower-like nanomaterials of Au and Pt were synthesized. The outline and contents of this dissertation were as follows:Chapter one was a brief introduction of the research background of this work, in which a review of nanomaterials and ILs are present, and then the history and recent progress in the preparation of nanomaterials associated with ILs are reviewed. The objective and the scientific significance of this dissertation were also pointed out at the end of this part.In Chapter two, the preparation of silver nanorods in the presence of IL 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF4) was investigated in detail. First, the shape of products was conformed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Then the growth direction was verified through the high resolution transmission electron microscope (HRTEM) and electron diffraction (ED). The formation mechanism was investigated by exploring the influence of time and other modulators on the products. The results demonstrated that the silver nanrods evolved from multiply twinned nanoparticles with a decahedral shape along (111) facet. Low interface tensions of bmimBF4 result in high nucleation rates, very small particles can be generated which undergo Ostwald ripening. BmimBF4 played a crucial role in the process. Moreover, the synthesis process was simplified to a "one-step reaction", and the reaction time was shortened to three hours. The products were silver nanorods with uniform dimension and shape all the same. The optical property of nanorods was investigated by UV-Vis spectra. The results showed silver nanorods possessed well surface plasmon resonance (SPR). Whats more, the surface-enhanced Raman scattering (SERS) of self-assembled silver nanorod array film with the Rhodamine 6G (R6G) as the probe molecule was also investigated. The results demonstrated that using the array film substrate could detect SERS signal of R6G even that the concentration of R6G was very low.In chapter three, the synthesis of flower-like Au/Pt nanomaterials in the presence of ILs 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF4) and 1-dodecyl-3-methylimidazolium bromide (C12mimBr) was investigated. The dimension and morphology of the products were characterized by SEM and TEM. The purity was confirmed by electron energy disperse spectroscopy (EDS). The crystal was proved by electron diffraction (ED). The results demonstrated that flower-like nanomaterials were formed by self-assembled nanoplates. This self-assembly process was supported byπ-πstack interaction of the neighboring imidazolium rings of bmimBF4. Furthermore, the mass ratio between C12mimBr and bmimBF4 played an important role in the formation process.