Study On The Ionic Liquid Assisted Synthesis Of Functional Nanomaterials

Inorganic nanomaterials have attracted much attention for their unique chemical and physical properties compared with the bulk solids. Because of the size and shape-dependent properties of the inorganic nanomaterials, synthesis of inorganic nanomaterials with controlled size and shape becomes a hot scientific research area. As a new green solvent, ionic liquids have some specific functions. Ionic liquids can be used to fabricate inorganic nanomaterials with unprecedented and sometimes unique structures and properties, thus they will open a new way for the preparation of nanomaterials. However, the formation mechanism of the inorganic nano-materials grown in ionic liquids and their properties are still in the primary stage. Base on this, we prepare zinc oxide (ZnO) nanomaterials and carbon nanotubes/platinum (CNTs/Pt) nanocomposites by ionic liquid-assisted synthesis approach in this thesis. The products are analyzed and characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), fluorescence spectrophotometer (PL) and so on. The formation mechanism of the inorganic nanomaterials in ionic liquids and their properties are investigated in detail to uncover their formation mechanism and to evaluate their advantages in properties. The content of the thesis can be summarized as follows:In Chapter1, the characteristics and preparation methods of nanomaterials are briefly introduced. Simultaneously, the structure and properties of ionic liquids are introduced. Besides, the applications of ionic liquids in the synthesis of inorganic nanomaterials are introduced. Based on the above, the purpose and main contents of the present thesis are proposed.In Chapter2, fast synthesis of nanostructured ZnO particles from an ionic liquid precursor tetrabutylammonium hydroxide (TBAH) by a microwave-assisted method is investigated. TBAH serves as solvent, microwave absorption agent, reactant and template in the system, which is very simple. The effects of zinc salt concentration, kinds of zinc salt and the water amount in ionic liquids on the ZnO products are investigated. The typical ZnO products are ZnO spheres constructed by nanoparticle subunits. Flower-like particles, nanoplates and nanoplate-assembled aggregates are also obtained by controlling the reaction conditions. The formation mechanism of the synthesized ZnO particles is attributed to the assembly of the primary ZnO nanoparticles based on the experiments. The room temperature photoluminescence spectra for the synthesized ZnO products shows a broad green fluorescence peak centered at around575nm, which indicates that there are a lot of oxygen defects in the ZnO lattice. In addition, the photodegradation experiments of Rhodamine B using our synthesized ZnO products demonstrate they had highly photocatalytic activity. This indicates that the obtained ZnO may have a wide application in the photocatalytic area.In Chapter3, aligned ZnO nanostructures are simply synthesized on zinc foil in different ionic liquid precursors (tetrabutylammonium hydroxide, TBAH; tetraethylammonium hydroxide, TEAH; tetramethylammonium hydroxide, TMAH; benzyltrimethylammonium hydroxide, BTMAH). The morphologies of products include: ZnO hexagonal rods, ZnO hedgehog-like spheres and ZnO platelets. The effects of various kinds of ionic liquids and their concentrations on the morphologies of the synthesized ZnO are studied. It is found that the kinds of ionic liquids play an important role for the formation of the final aligned ZnO particles. This could be attributed to the different structures of the ionic liquids, which make the electrostatic interaction between the cation of the ionic liquid and the primary ZnO nanoparticles different. In order to satisfy the requirement of various nanodevices, the controlled patterning of nanostructured materials on surfaces becomes very important. We successfully construct various aligned ZnO particles on zinc foil by a simple ionic precursor route, which may open the door for the development of new kinds of ZnO nanodevices.In Chapter4, carbon nanotubes/platinum (CNTs/Pt) nanocomposites are successfully synthesized with the assistance of1-butyl-3-methylimidazolium chloride ([BMIM]Cl) ionic liquid as a linker and ascorbic acid (AA) as a reducing agent. The effects of ionic liquid concentration and platinium salt concentration on the final CNTs/Pt products are investigated to reveal the optimum synthesis condition. The results show that the concentration of ionic liquid greatly influences the size and the distribution of Pt nanoparticles on the surfaces of the CNTs. The size of Pt decorated on CNTs decreases with the increase of the ionic liquid concentration. According to the experimental results, a possible formation mechanism is proposed based on the π-π interaction between the ionic liquid and the carbon nanotubes. Cyclic voltammetry tests are used to characterize the electrochemical response of the as-prepared CNTs/Pt nanocomposites to K3Fe(CN)6. It is observed that the as-prepared CNTs/Pt nanocomposites had an improved electrochemical response. It demonstrates the electrochemical response increases with the decrease of the Pt particle size. In addition, the synthesized CNTs/Pt nanocomposites can efficiently catalyze the methanol oxidation process. The present synthesis route is simple without additional additives, which might have wide applications in the synthesis of carbon naotube-based nanocomposites.In Chapter5, the conclusions of this paper are summarized. Besides, the innovations and inadequacies of the thesis are also introduced.