Preparation Of CdS Nanocrystals In Ionic Liquids And Preparation Of Ⅱ-Ⅵ Nanoparticles By Applying Alternating Electric Field

The synthesis of nanomaterials has become a very important research object and has profound impact on the development of future economy and society.In general, nanoparticles are defined as tiny solid particles with size between 1nm and 100nm.As the particle size approaches nanometer scale,their peculiar physical and chemical properties become quite different with broad application potentials.Many methods can be utilized to synthesize nanomaterials.Generally,gas,liquid, and solid phase reactions are the three most important methods.Liquid-phase synthesis is widely used to prepare nanomaterils in solvents.However,it is not conducive to mass production for its disadvantages like pollution,high cost,rigorous reacting conditions and expensive equipments.So we prepared CdS nanocrystals with particular morphologies in ionic liquids system at 180℃.And a novel method was proposed in preparing nanoparticles using alternating electric fields.Uniform CdE(E =S,Se,Te)nanoparticles with regular morphology can be obtained in room temperature and ambient pressure.Firstly,a novel crystal,[BMIM]₂[Cd₂(SCN)₆]with interesting structure architecture was synthesized.Our results show that the dimension of inorganic-organic framework can be rationally designed by alternating the size of the filled cations.Also the photoluminescence properties of the compound have been studied.Secondly,dendritic CdS nancrystals about 5um with branches 200nm×500nm was prepared in ionic liquids system.XRD results indicate that the products are single crystals with hexagonal structure.The concentration of ionic liquids,reactants, surfactants and reacting temperature all play important roles in the final morphologies of CdS nanocrystals.The reacting process was studied and the mechanism governing the growth of CdS nanocrystals was discussed.Thirdly,we prepared CdS dendritic nanocrystals(1um×3um),CdSe nanorods (50nm×400nm)and CdTe nanoparticles(500nm)by hydrothermal method.XRD results indicate that the products are single crystals with hexagonal structure in CdS and CdSe and zinc-blende structure in CdTe.After applying an alternating electric field,uniform spherical nanoparticles with regular morphology were obtained and then were characterized by FESEM.The effect of voltage and frequency of electric field on the products was studied.A possible mechanism is proposed to explain the dividing process of CdE nanocrystals.The dipole moment of dipolar materials was the prerequisite for preparing nanoparticles.In summary,systematic investigations have been conducted on the growth, crystal structure,optical properties of[BMIM]₂[Cd₂(SCN)₆],the preparation,growth mechanism of dendritic CdS nanocrystals and the preparation,dividing mechanism of uniform CdE nanoparticles.Some important and novel experimental results have been obtained.