Selenium And Its Silver Selenide - Polymer Composite Microspheres Of Microgel Template Was Prepared

In recent years, the template techniques for preparing composite microspheres with special structures and properties have received considerable interest in materials science field. The feature of template method is that to effectively control the surface morphologies and structures of produced composites by using their space confinement and controllable effects on as-prepared materials. Therefore, it is easy to obtain the composites with unusual surface morphologies as well as the better hybridization between produced nanoparticles and template materials. Comparing to other polymeric templates, polymeric microgels have particular advantages of simple synthesis and adjustable chemical functionality, and their sizes varied from nano- to microscale by choosing appropriate polymerization technique. More importantly, microgels have distinct stimulus-responsive volume changes, and the stimuli could be temperature, pH, ionic strength, electric and magnetic fields, etc.In recent ten years, application of micro-gels as micro- or nanoreactors for the preparation of inorganic nanoparticles has been intensively explored. Based on the unique physical and chemical properties of polymer microgels, our group proposed a novel route for preparing inorganic-polymer composite microspheres with patterned surface structures by a polymer microgel template. By employing this technique, a variety of hybrid inorganic-polymer microspheres with patterned surface structures have been synthesized in our laboratory, such as metal sulfide-polymer composite microspheres, inorganic insoluble salt-polymer composite microspheres, oxides-polymer composite microspheres, metal sulfide-polymer composite microspheres and so on. The application of the polymeric microgel template method was extended for the preparation of selenium and metal selenide-polymer composite microspheres. In this study, we focus on research interest on the controllable synthesis of selenium and silver selenide-polymer composite microspheres with patterned surface structures. This thesis includes two parts as follows:(1) Polyacrylamide (AM) polymer microgels were prepared by an inverse suspension polymerization method. At room temperature, PAM microgel acting as template, Ag2Se-polyacrylamide (Ag₂Se-PAM) composite microspheres with patterned surface structures were prepared by combination of a polymer microgel template method and a reverse micelle technique using AgNO₃ as Ag⁺ and Na₂SeSO₃ as Se^2- ion sources, respectively. Scanning Electron Microscope (SEM), Thermogravimetric analysis (TGA) techniques and X-ray Powder Diffraction (XRD) were used to characterize the morphologies of composite microspheres, the content, and the lattice of inorganic Ag₂Se. It was demonstrated that the surface morphology of the prepared composite microspheres was influenced by the initial concentration of AgNO₃ and the dosage of the used surfactant. The proposed method can also be used for the preparation of other metal selenide-polymer composite microspheres, such as CdSe-PAM, CuSe-PAM, ZnSe-PAM, and so on. This route might provide a better foundation for controlling synthesis of metal selenide-polymer composites with surface patterned structures.(2) The PAM microgels were used as template for the preparation of Se-PAM composite microspheres with surface special structure by different methods including inverse suspension method and gas phase method, with hydrogen chloride gas inducing the disproportionation reaction of Na₂SeSO₃. Scanning Electron Microscope (SEM), and X-ray Powder Diffraction (XRD) were used to characterize the morphologies of composite microspheres, and the lattice of inorganic Se. In this paper, the effects of the initial concentration of Na₂SeSO₃ and the concentration of hydrochloric acid were mainly studied. It was found that the Se-polymer composite microsphere might have various surface structures by choosing appropriate initial concentration of Na₂SeSO₃, and modulating the rate of disproportionation reaction. Furthermore, it is expected that the proposed method can be also created a novel route for the preparation of semiconductor nanomaterials with more complicated morphologies.