Morphology Controllable Synthesis, Characterization, And Properties Of Functional Semiconductor Nanomaterials

Functional semiconductor nanomaterials have wide potential applications in catalysis, sensors, electronics, photonics, optoelectronics, solar cells, and nanodevices, due to their excellent catalytic, sensing, electrical, optical, thermal, and magnetic properties. Moreover, it has been demonstrated that these properties are strongly dependent on the size and shape of nanomaterials. Over the past few years, therefore, a lot of efforts have been made for the fabrication and control of size and shape of functional semiconductor nanomaterials. However, these traditional methods usually have some disadvantages of time consuming, high temperature needing, expensive, and not practical for scale-up and commercialization. In contrast to the traditional methods, solution chemistry based so-called"soft"approaches can provide an alternative, convenient, lower temperature, and environmentally friendly pathway for fabrication of advanced inorganic materials with desirable shapes and sizes.Ionic liquids, as green and efficient recyclable solvents, have gained a great deal of both academic and industrial attention as a new class of compounds for a potential effective green replacement of conventional organic solvents. As a burgeoning field, ionic liquids have been employed as solvents, reactants, or templates for the preparation of inorganic nanomaterials, due to their highly favorable properties, such as innocuity, extremely low volatility, good thermal stability, good dissolving ability, wide liquid temperature range, designable structures, high ionic conductivity, and so on. In this dissertation, ionic liquids have been used to synthesize nitrides and oxides nanostructures with high performance and novel properties.The main objectives of this dissertation are as followed:(I) Various functional semiconductor nanomaterials, including turbostratic Boron Nitride (t-BN) nanoflakes, hematite (a-Fe2O3) with various morphologies, and gamma-aluminum oxide (γ-Al2O3) mesoporous nanoflakes have been successfully synthesized via an ionothermal or ionic liquid-assisted hydrothermal synthetic method under mild condition. It is worth noting that the ionothermal synthesis of nitrides is reported for the first time. It is also the first time to successfully synthesize γ-Al2O3 mesoporous nanoflakes by one-step ionothermal synthetic method at 150℃, which is the lowest reaction temperature ever reported for the one-step synthesis of nanocrystalline y-Al2O3.(II) In the reaction system, the ionic liquid, a green recyclable solvent, is used as multifunctional materials in terms of precursor, solvent, and template. It has been demonstrated that the physicochemical properties of the ionic liquids have strong effects on the reactivity, shapes, sizes, and phases of the target products, since their properties such as polarity, viscosity, and softness strongly influence the solubility and transport behavior of the precursors under thermal conditions. The effects of the ionic liquid have been investigated systematically in the dissertation.(III) The proposed formation mechanisms have also been investigated on the basis of detailed experimental data and the hydrogen bond-co-π-πstack mechanism is used to be responsible for the present formation of these nanostructures.(IV) The shape and size-dependent properties of these nanostructured nitrides and oxides have also been investigated in depth.(V) The products have been characterized by several measurements, such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible spectroscopy (UV), photoluminescent spectroscopy (PL), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscope (FE-SEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM).In summary, we presented some facile and environmentally friendly ionic liquids-based approaches for the morphology controllable synthesis of functional semiconductor nanomaterials in this dissertation. It has been demonstrated that the ionic liquid possessing the extraordinary potential is favorable for the fabrication of nanomaterials with novel morphologies and improved properties. The present synthetic strategy is expected to prepare other kinds of nanomaterials, having distinct characteristics and properties.