Study On The Solution-based Chemical Control Synthesis And Physical Properties Of Chalcogenide Semiconductor Namomaterials

In this dissertation, solution-based routes were developed to realize the chemical synthesis and simultaneous assembly of one-dimensional (1D) nanostructures. This dissertation aims at searching for new chemical synthesis routes to synthesize chalcogenide semiconductor nanomaterials, control the morphology of the products by adjusting the reaction conditions. The as-prepared products are applied in different fields to check their performance, and it is expected that the products possess some novel physical and chemical properties. The details are summarized as follows:1. A general monodentate-amine-based solvothermal approach in a binarysolution made of distilled water and ethanol amine has been designed to preparechalcogenide semiconductor nanomaterials (ZnS,ZnSe,CdS,CdSe,MnS,PbS etal.). We successfully realize selective-controllable synthesis of various novelnanostructures by adjusting the reaction conditions (such as the molar ratio of thereactants, the volume ratio of the mixed solvents and the reaction temperature et al.).We investigated the formation process of ZnS microspheres constructed from theassembly of nanorods and fan-like CdS nanorod bundles, and proposed rationalgrowth mechanism. Futhermore, this is the first time to synthesize wurtzite ZnSeultrathin nanobelts in solution. Meanwhile, the Photocatalytic Properties of II-VIsemiconductor nanomaterials is another focus in our research. ThisL-cysteine-assisted method could be extended to access other semiconductornamomaterials with novel morphologies and structural specicality. The above resultsof research have been published in Advanced Functional Materials, Chemistry - AEuropean Journal, Crystal Growth & Design, respectively.2. A mixed solvent system made of ethylenediamine and water has been developed to prepare CdS namomaterials. Monodisperse microspheres constructed from the assembly of nanorods, polypod spherical structures, urchin-like spheres and ultra-long nanowires can be achieved by adjusting the volume ratio of the mixed solvents. We also probed into the growth of microspheres constructed from the assembly of nanorods, and proposed a rational growth mechanism. The result of research has been published in Chemistry -A European Journal.3. A ternary mixed solvent system made of ethylenediamine-water-hydrazinehydrate (N₂H_·4H₂O) has been designed to prepare ZnSe precursor. Hexagonal wurtziteZnSe nanowire bundles of a pure phase were synthesized by annealing a precursor(ZnSe·3ethylenediamine) at 600°C under a pure argon atmosphere for 4-6 h. it isfound that the morphology of the final products were controlled by the precursor.Using ZnSe nanowires as templates, we successfully synthesized a kind ofwell-defined SiO₂/ZnSe composite nanostructures at ambient temperature. Comparedto bare ZnSe nanowires, these composite nanostructures greatly improve their thermalstability and optical properties. The above results of research have been published inAdvanced Functional Materials and Journal of Nanoscience and Nanotechnology,respectively.4. A hydrothermal method was developed to prepare 1D t-Se nanostructure with the assistance of poly (vinyl alcohol) (PVA). Large-scale single crystalline selenium nanoneedles were fabricated using PVA serve as both a reductant and a polymer-structure-directing reagent. Based on the evolution process of nanostructures at various growth of the reaction, a possible mechanism was proposed to the formation of nanoneedles, which involved a solid-solution-solid transformation process in the assistance of PVA. The result of research has been published in Crystal Growth & Design.