Abstract |
Microporous materials and mesoporous aluminosilicates marked the beginning for the synthesis of materials that have organized porous. Next step was the development of materials that would combine the uniform and organized porosity with important catalytic, attributes of transition metal oxides. Although microporous and mesoporous oxidic materials are considered very promising for applications they do not exhibit interesting optical, electronic or photonic properties. This is because the inorganic framework is insulator. The combination of optoelectronic or semiconducting properties with porosity in one material could open the pathway for advanced applications. Therefore, the development of non-oxidic porous solids based on metal-chalcogenides have attracted significant attention during the last year.
In the first part of this thesis, a new method was developed that allow the synthesis of the salts (R4N)
4[Sn4Q10], (R = methyl or ethyl,Q=S, In, Te). These salts contain the molecular adamantane clusters [Sn4Q10]4- and can serve as soluble precursors for the synthesis of a large family of open-framework compounds (Me4N)2M[Sn4Se10] (M=Mn2+,Fe2+, Co2+, Zn2+) and (Me4N)2Mn[Ge4Te10], using simple metathesis reactions.
In the second part, the synthesis of surfactant templated mesostructured semicoducting solids, based on chalcogenide anions [SnSe4]
4- and [Sn2Se6]
4- was studied for first time, in aqueous solution. These particular anions in the presence of surfactant molecules and linking metal cations such as result in the formation mesostructured solids. The degree and the type of pore organization (hexagonal, cubic or lamellar) is controlled by a) the nature of the surfactant in terms of both chain length and head group type and b) the ratio of [SnSe4]
4- /[Sn2Se6]
4- on the initial mixture.
Furthermore we developed a new synthetic methodology based on neutral surfactant molecules such as the block co-polymer polyethylene-polypropelyne-polyethylene oxide (EO20PO70EO20, P123). In the system P123/Zn/[Sn2Se6] after calcination at 350 oC shows a surface area of 88 m2g-1 and pore size ~100 Å.
All solids were characterized with X-ray diffraction (PXRD), thermogravimetric analysis (TGA), elemental analysis, Raman and Mössbauer spectroscopy, scanning electron microscopy coupled with energy depressive spectroscopy (EDS) and transmission electron microscopy (TEM). The optical properties were studied with solid state UV-vis/nearIR diffuse reflectance spectroscopy.
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