Liquid-phase Synthesis And Modification Of Colloidal Particles

Colloidal particles are very common in nature and also have numerous industrialapplications, such as in ceramics, pigments, coatings, cosmetics, recording materialsand countless others. The optical, electric, magnetic, adsorptive, catalytic and otherproperties of colloidal particles depend strongly on their size, morphology andchemical composition, so the synthesis of uniform colloidal particles has been themajor goal of chemists. The most studied and best established examples of suchcolloidal particles are monodisperesed silica spheres and polymer latexes. Thesematerials, however, do not exibit any particularly interesting optical, nonlinear opticalor electro-optical functionality. There are two ways to solve this problem. One is tocoat silica or polymer latexes with other materials, and the other is to develop newmethods to prepare other monodispersed colloidal particles. Therefore in this thesis,two aspects of research work were carried out: liquid-phase synthesis of uniformsemiconductor colloidal particles through microemulsions or template method, andthe modification of monodispersed silica spheres.CdS nanocrystals, microspheres and nanospheres were prepared in water-in-oilmicroemulsions, hydrothermal microemulsions and oil-in-water microemulsions,respectively. By adjusting the molar ratio of reactant ions, the morphology of AgIcolloial particles such as nanoparticles, nanorods and nanoweirs could be wellcontrolled in microemulsions.Using active ZnSe as template, Ag₂Se, Cu_2-xSe, CdSe, ZnO, ZnS and CdShollow microspheres were successfully synthesized via the chemical conversionmethod. ZnSe/CdS , ZnSe/ZnS core-shell spheres and ZnSe-ZnO, ZnSe-ZnScomposite spheres could also be obtained in the same way.In respect of modification of monodispersed silica spheres, Eu-doped, Tb-dopedand Eu,Tb-codoped fluorescent silica nanospheres were prepared in microemulsions.Their optical properties were characterized. In view of the surface charge of colloidalparticles, a new method was developed to coat silica spheres with Au, Agnanoparticles. Finally using SnCl₂ as precursor, silica spheres modified with SnO₂nanoparticles were well studied.