Functional Ionic Liquids Assisted Synthesis And Characterization Of Metal Sulfide Or Selenide

Inorganic nanomaterials have attracted much attention for their unique chemical and physical characteristics in photics, magnetics, electricity, mechanics and biology. The interesting size and shape dependent properties of the inorganic nanomaterials make the scientists endeavor to prepare inorganic nanomaterials with controlled size and structure and explore their potential applications. In order to synthesize the inorganic nanomaterials with designated architecture and property, scientists usually combine water with traditional organic solvent or additive in conventional synthesis. Organic solvents have diverse physicochemical properties, such as density, polarity, solubility, and liquidus range, but most of them have low boiling points, highly toxic and high vapor pressures, additionally, the solubility of inorganic reactants in these solvents is low. In particular, the high vapor pressures and toxicity of certain volatile organic solvents may cause significant environmental problems. Therefore, a low toxic and vapor pressure substance with tunable and versatile properties replaced traditional organics for conducting materials synthesis have been actively sought.Ionic liquids (ILs) are liquid molten salts composed of organic cations and organic/inorganic anions. They are a set of environmentally benign solvents with excellent chemical and thermal stabilities, good electrical and thermal conductivity, nonvolatilities or neligible vapor pressure, a broad range of room temperature liquid compositions, and selective solvency and design. With these advantages, ionic liquids are fitted well with the developed topic of green chemistry and conquer some difficults. Use of ionic liquids in electrochemistry, organic chemistry, catalysis, analysis and so on, has been extensively studied, but their use in inorganic synthesis has just begun. The role of ionic liquids played in the synthesis of inorganic materials are altered gradually, from beening single solvents, templates or surfactants to diverse roles that can act as templates and precursors to inorganic materials, as well as solvents and reactants.In this dissertation, we synthesized three functional ionic liquids based on common ones and used these to prepare various micro/nanomaterials, including cadmium sulfide (CdS) dendrites, cadmium selenide (CdSe) nanospheres and lead sulfide (PbS) nanoplates. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-vis absorption spectroscopy and photoluminescence (PL) emission spectroscopy were used to investigate the phase structures, morphologies and optical properties of as-prepared materials.(1) Cadmium sulfide (CdS) dendrites were successfully synthesized through a facile template free solution approach, using an ionic liquid 1-n-butyl-3-methyl-imidazolium thiocyanate ([BMIM]SCN) and cadmium chloride (CdCl2 as raw materials, where the functional ionic liquid acted both as sulfur source and surfactant. A possible mechanism for the formation of CdS dendrites has been proposed. The photoluminescence (PL) spectrum displayed two distinct peaks. The weak one is a green emission band at 510 nm and the intense is an infrared band at 710 nm, which are diverse to those in previous reports.(2) Cadmium selenide (CdSe) nanospheres consisted of nanoparticles were successfully prepared using the precursor ([BMIM][Cd(SCN)3]) as template and sodium selenosulfate (NaSeSO3) as raw materials. The precursor was fabricated in large scale through the reaction of ionic liquid 1-n-butyl-3-methylimidazolium chloride ([BMIM]Cl), potassium thiocyanate (KSCN) and cadmium chloride (CdCl2) under ambient conditions. In addition, the influence of the reaction time, temperature and pH Value on the structure, textural properties and morphologies of the final products were detailedly investigated as well as the optical properties.(3) Lead sulfide (PbS) nanoplates constructed by nanocubes were successfully prepared by functional ionic liquid ([BMIM]Gly) assisted process at 120℃, using the ordinary sulfourea (NH2CSNH2) as sulfide source and lead nitrate (Pb(NO3)2) as lead source. Through varying the experimental parameters such as reaction temperature and reactant molar ratio, we could controlled construction of PbS nanostructures and demonstrated that the formation of PbS nanoplates underwent three stages:nucleating, growth and self-assemble. The optical properties of as-prepared PbS samples were different from previous reports.