Study On The Solution-based Chemical Synthesis And Formation Mechanism Of Chalcogenide And Oxide Nanomaterials

Based on the chemical solution-phase synthesis,the aim of this dissertation is to explore the synthesis of CuS,NiTe₂,Cu₂O,CuO nanomaterials by room temperature chemical solution route,solvothermal technique and hydrothermal method.A chemical solution route has been developed to selectively prepare covellite(CuS) nanotubes and hollow nanospheres at room temperature;Single-crystalline NiTe₂ nanoplates with the hexagonal shape have been synthesized on a large scale through a hydrothermal method.Well-aligned arrays of cuprous oxide(Cu₂O) nanowires have been synthesized by an ethylene glycol-reduced process;Three-dimensional(3 D) CuO hierarchical microspheres have been prepared via a simple hydrothermal route.The morphologies and structures of as-prepared nanomaterials are characterized in detail.A systematic investigation has been carried out to understand the factors influencing the phase composition and morphology,and their formation mechanisms are also briefly discussed.The main contents can be summarized as follows:1.A chemical solution route has been developed to synthesize CuS nanostructures through the precitation reaction of CuCl₂·2H₂O,thiourea(Tu) and NaHCO₃ in distilled water at room temperature.By regulating the concentration of Tu,CuS nanotubes and hollow nanospheres with diameters of 100-200 nm have been selectively prepared.Structural characterizations indicate that both nanotubes and hollow spheres are composed of CuS nanoparticles with diameters of about 5-10 nm.A systematic investigation has been carried out to understand the factors influencing the CuS morphology.Two different routes are identified to explain the formation of the nanotubes and hollow nanospheres herein.It is concluded that low concentration of Tu is favorable to CuS nanotubes via the thiourea-copper(â…¡) complex precursor route,while high concentration is favourable to CuS hollow spherical structures via the thiourea-copper(â… ) complex precursor route.UV-vis absorption spectra show the CuS product with hollow nanosphere morphology shows a wide absorption peak centered at about 481 nm,while the product with nanotube morphology shows no such peak.Room-temperature PL spectra of CuS hollow nanospheres reveal a peak at around 432 nm,while no such peak for CuS nanotubes.UV-vis absorption and room PL spectra display different morphology-related absorption phenomena for nanotubes and hollow nanospheres. The experimental conditions are mild,and the manipulations are convenient. These results were published in J.Nanosci.Nanotechnol.(2007,7,4501).2.Single-crystalline NiTe₂ nanoplates have been synthesized on a large scale through a hydrothermal reaction of Ni(CH₃COO)₂ and YeO₂ at 210℃for 48 h.The NiTe₂ nanoplates have hexagonal shape.The average edge sizes and thicknesses of nanoplates are 350 nm and 85 nm,respectively.Here,Ethylenediaminetetraacetic acid(EDTA) is employed as a chelating agent.Furthermore,EDTA plays crucial roles in controlling phase composition and morphology of the resultant products. The simple process,mild conditon and cheap cost in this work make the present route attractive and significant.It has potential industrial application.This method may be extended to prepare other tellurides nanomaterials.This study was published in J.Nanosci.Nanotechnol.(2009,9,2715).3.Well-aligned arrays of Cuprous oxide(Cu₂O) nanowires were synthesized through the reduction of Cu(CH₃COO)₂ by ethylene glycol(EG) without the assistance of externally introduced template and surfactant.The panorama of well-aligned arrays of Cu₂O nanowires looks like a biscuit.These Cu₂O nanowires are～30 nm in diameter.A systematic investigation has been carried out to understand the factors influencing the phase composition and Cu₂O morphologies.The experimental system is simple and the manipulation is convenient.This study was published in Mater.Chem.Phys.(2009,114,213).4.A simple hydrothermal route was developed to synthesize CuO three-dimensional (3D) hierarchical microspheres using CuCl as the copper source and PEG as the morphology-directing agent in ammonia aqueous medium.The microspheres with average diameter of about 3μm were constructed from two-dimensional(2D) nanosheets with average thickness of about 40 nm via a layer-by-layer growth style and the nanosheets were composed of tiny nanoplates through orientation attachment.The quantity of PEG played crucial roles in the formation of CuO hierarchical structures and a systematic investigation was carried out to understand the factors influencing the CuO morphology.The possible growth mechanism was identified to explain the formation of CuO architectures herein.