Solution Synthesis And Mechanism Research Of One-dimensional Nanomaterials

In this dissertation, based on the hydrothermal and sonochemical methods, new wet chemical synthesis routes were explored to prepare one-dimensional (1D) nanomaterials. 1D nanostructures including nanowires, nanobelts, nanotubes and nanoplates of various hydroxides and carbonates materials, such as nickel hydroxyl sulfate (Ni(SO₄)_0.3(OH)_1.4), cadmium carbonate (CdCO₃), alkaline stannates and carbonates were synthesized by designing possible chemical reactions and controlling the experimental parameters. Porous 1D nanostructures of their corresponding metal oxides were also obtained through heat treatments. At the same time, their growth mechanisms were also studied. The experimental details are summarized as follows:(1) Nanobelts of nickel hydroxyl sulfate have been prepared on a large scale via a simple template-free hydrothermal reaction on the basis of a complex [Ni(NH₃)₆]²⁺ formed with Ni²⁺ and ammonia in an ethanol-water solution. Furthermore, nanostructures of mixture of crystralline NiO and amorphous nickel sulfate with various morphologies, such as nanobelts, porous nanobelts, and nanoparticles, were obtained by thermal treatment of the as-synthesized Ni(SO₄)_0.3(OH)_1.4 nanobelts at different temperatures. Based on the temporal-dependent SEM and XRD evidences, we could find that that the sulfate group inserting should be responsible to the shape transformation from layer structure to nanobelts. As a matter of fact, our experiments may provides a general, simple, and effective method to control the shape of single-metal layered hydroxy salts in aqueous solution, and are also suitable to the synthesis of other hydroxide double salts (HDSs) and layered double hydroxides (LDHs) which contain i.e.Cd²⁺, Zn²⁺, Cu²⁺, Co²⁺ and Co³⁺ ions.(2) Low-dimensional single crystalline CdCO₃ nanostructures such as nanowires, nanobelts, nanorolls and 1D hierarchical structures have been successfully synthesized through a convenient, low-temperature hydrothermal method. The influences of ammonia concentration, reaction time and temperature on the morphologies of CdCO₃ were investigated. In addition, these low-dimensional nanostructures could be transformed into oriented CdO nanoporous structures through heat treatment process, and the corresponding shapes can be preserved completely.(3) We have used the sonochemical approach to firstly synthesize CaSn(OH)₆ single crystal nanotubes, and various single crystals anisotropic shapes of CaCO₃ such as nanowires, nanosheets and unusually obtained nanoplates without using any template at room temperature. The complex interplay between crystallization processes and self-assembly resulting from spatial constrains had been investigated through studying the structural evolution of metastable intermediates synthesized. crystallization pathway involved in nanotubes and nanowires formation under the condition of sonication. Moreover, this approach is suitable to the anisotropic single crystals synthesis of other alkaline earth stannates and carbonates such as SrSn(OH)₆, BaSn(OH)₆, SrCO₃ and BaCO₃. It also gives a new demonstration of sonochemical effects on the crystallization and assembly of block building in the mesoscale.