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Identifier

000352721

Title

Σύνθεση, χαρακτηρισμός και μελέτη των οπτοηλεκτρονικών και καταλυτικών ιδιοτήτων νέων ημιαγώγιμων νανοδομημένων και νανοπορώδων υλικών

Alternative Title

Synthesis, characterization and study of the optoelectronic and catalytic properties of new semiconductive nanostructured and nanoporous materials

Author

Τσαμουρτζή, Κωνσταντίνα Ν.

Thesis advisor

Τρικαλίτης, Παντελής

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.

Language

Greek

Subject

chalcogenides

mesostructured materials

microporous

semiconductors

surfactants

template

ανιόντα μετάλλου-χαλκογονιδίου

εξαγωνική και κυβική διευθέτηση πόρων

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