The Preparation And Characterization Of MS(M=Pb, Zn, Cd)/Polymer Nanocomposites By Microemulsion

Semiconductor MS(M=Pb,Zn,Cd) nanoparticles, have been investigated intensively during the past few years due to their unique chemical and physical properties and wide application in nolinear optics, light emitting diodes, and so on. Whereas, nanoparticles are highly unstable, and in the absence of a trapping media, they agglomerate extremely quickly. For this reason, bonding of capping agents to nanoparticles is necessary to provide chemical passivation, control size and morphology, and also improve the surface state which has significant influence on the optical and electronic properties of nanoparticles. In this thesis, the impact of polymers on the size morphology, stability and optical properties of the obtained nanocrystals has been investigated.Microemulsion method has received more and more attention for the last decade, and its application has become popular, because it enabled easy operation and controlling of size particles possible with simple experimental apparatus. In the field of preparation of nanometer particles, it has its own unique advantage. The paper delt with the microemulsion-forming condition, made efforts to determine the suitable surfactant on relation between conductivity and quantity of dissolved water. And a series of experiments had been conducted, on the basis of that, favorable reaction conditions were fixed, and influencing factors including cryodesiccation means, the time of aging and so on have been ranked. The results indicated the optimal value of the water-to-surfactant molar ratio(R) is 3～16, the effect of vacuum desiccation is good and the nanoparticles get bigger as the function of aging time.Semiconductor MS(M=Pb, Zn, Cd) nanoparticles, which were coated with polymer are prepared in n-heptane /sodium bis(2-ethylhexyl) sulfosuccinate (AOT) /water microemulsions. Through the reaction of M2+ with the S2– ions that are slowly released from Na2S, the MS nanoparticles were synthesized, then the monomer was dropped into the mixed microemulsion system.After polymerization, the composite was successfully obtained.The granularity and surface morphology characteristics of the nanoparticles prepared by microemulsion were presented by transmission electron microscopy (TEM). The crystallographic forms of the particles were tested by X-ray diffraction (XRD), and the results were in accordance with the TEM. Luminescence property of products were characterized by ultraviolet absorption (UV-Vis) and fluorescence spectrum(FL), which showed evident characteristics of nanoparticles for there were blue shift in the spectrums. Due to the excellent capabilities of optics and electrics and photoelectric, the nanocomposite can be used in many fields.