Ph.D. (Doctor of Philosophy)
Department of Chemistry and Biochemistry
Synthesis of complex functional inorganic and hybrid material is desirable because complex composition allows more degree of freedom and tunable materials where the properties differ from those of their parent components. As a test of concept, we have synthesized a series of LnMOFs with the general formula of [Ln(NDC)(DMA)2(NO3)]n (Ln=Ce, Nd, Sm, Eu, Tb, Yb). These materials are isostructural, adopting the orthorhombic P b c a space group. They are relatively stable under drying and heating treatment and have more metal coordination numbers compared to transition metal MOFs. There are theoretically sizable channels and free space inside the structure, allowing them to absorb certain molecules or ions with specific size and shape. Among guest molecules tested, chromate ion (CrO42-) and o-phenanthroline in general shows most prominent fluorescence quenching effect in most of the LnMOFs due to the energy of their lowest unoccupied molecular orbitals (LUMOs) being closest to that of the conduction band minimum (CBM) of the LnMOFs, allowing a better interaction and alignment of energy levels between them and the LnMOFs.
We also synthesized multifunctional inorganic compounds namely KAg3Sn2S6 and CsSb6S16 using a solvothermal method. The Ag3Sn2S6 crystallizes in a hexagonal crystal system with the P-62m space group. Its electronic partition shows K+(Ag+)3(Sn4+)2(S2-)6. This simple electronic partition suggests that there is no conducting electron within the structure. Electronic structure study revealed that there is no band gap within the material and the atomic contacts within the crystal structure give rise to its semi-metallic/metallic nature, making this compound a candidate as photoelectric material capable of absorbing photons from solar spectrum similar to graphite. As for ternary compound CsSb6S16, its structure determination reveals fused S12 rings embedded inside the Cs-Sb matrix. Electronic structure investigation applying Crystal Orbital Hamiltonian Population (COHP) calculations reveal that the S12 ring is a stable ring shown by the mostly positive COHP values for the sulfur-sulfur bonds and large positive integrated COHP values corresponding to strong covalent bonding. Electronic partition of the compound counts four sulfur atoms in the S12 ring as neutral S0 species. As this molecule is a neutral molecule, the electron partition become a resonance configuration between [(Cs+)(Sb3+)4(Sb5+)2(S0)4(S2-)12]- and [(Cs+)(Sb3+)3(Sb5+)3(S0)4(S2-)12]+ with mixed 3+ and 5+ oxidation state for Sb. This simple electron partition picture implies that the compound is metallic.
Ginting, Sura Menda, "Synthesis, Structures, Optical and Electronic Properties of Functional inorganic and Hybrid Materials" (2020). Graduate Research Theses & Dissertations. 7068.
Northern Illinois University
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