Several Inorganic Oxide Nanotubes In Liquid Phase Synthesis, Growth Mechanism And Its Application

The main challenge in the area of nanotechnology is how to precisely control the sizes, dimensionalities, compositions and crystal structures in nanoscale, which may serve as a powerful tool for the tailoring of physical/chemical properties of materials in a controllable way. Solution-based chemical methods have some advantages in the controllable synthesis of nanomaterials in their structure, morphology and dimension. In this dissertation, valuable explorations have been carried out to prepare inorganic nanotubes including CoO, Co3O4, Ni(OH)2 and Mg(OH)2 nanotubes using solution-based chemical methods, as well as their formation mechanism and the novel properties of the as-obtained new-type nanostructures. The main points can be summarized as follows:1. CoO, Co3O4, Ni(OH)2 and Mg(OH)2 nanotubes were synthesized by solvothermal treatment of corresponding colloidal hydroxide. These nanotubes were characterized by powder X-ray diffraction (XRD), selected area electron diffraction (SAED) and transmission electron microscopy (TEM). Advantages of this method include that it is a simple and general process without the need for a catalyst, surfactant or template, which is low cost and the raw materials are readily available. Based on the above results, other metal hydroxides with layered structure are therefore potentially capable of forming nanotubes. To the best of our knowledge, no studies have been reported on the preparation of CoO nanotubes.2. Based on the above time-dependent morphological evolution evidence, the growth of these nanotubes can be divided into three steps. At first, these amorphous precursors would form some nanoplates during the first stage. The first step lasted for about 1 h, and then some of these nanoplates were dissolved again to form some small growth entities (such as atomistic species or cluster building blocks) in the second step. And subsequently, these small growth entities reorganized to from large aggregations till the tubular nanostructures formed.3. Some larger superstructures are found in CoO, Co₃O₄, Ni(OH)₂ nanotubes and are suggested to be caused by ordered oxygen vacancie during formation.4. Ni and Co nanotubes were synthesized using the as-obtained CoO and Ni(OH)₂ nanotubes as template.5. Decoloration of wastewater containing direct dye by using Mg(OH)₂ nanotubes is studied. The result showed that the absorbing capacity of Mg(OH)₂ nanotubes is larger than commerical Mg(OH)₂ materials.6. We report that CoO and Co3O4 nanotubes in fact possess an intrinsic enzyme imietic activity similar to that found in natural peroxides. To investigate the mechanism of the peroxidase activity of these nanotubes, we determined apparent steady-state kinetic parameters for the reaction. Within the suitable range of H2O2 concentrations typical Michaelis-Menten curves were observed for both CoO and Co₃O₄ nanotubes.