Browsing by Subject "Fluorene"
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Item Open Access Cyclodextrin-functionalized mesostructured silica nanoparticles for removal of polycyclic aromatic hydrocarbons(Academic Press Inc., 2017) Topuz, F.; Uyar, T.Polycyclic aromatic hydrocarbons (PAHs) are the byproducts of the incomplete combustion of carbon-based fuels, and have high affinity towards DNA strands, ultimately exerting their carcinogenic effects. They are ubiquitous environmental contaminants, and can accumulate on tissues due to their lipophilic nature. In this article, we describe a novel concept for PAH removal from aqueous solutions using cyclodextrin-functionalized mesostructured silica nanoparticles (CDMSNs) and pristine mesostructured silica nanoparticles (MSNs). The adsorption applications of MSNs are greatly restricted due to the absence of surface functional groups on such particles. In this regard, cyclodextrins can serve as ideal functional molecules with their toroidal, cone-type structure, capable of inclusion-complex formation with many hydrophobic molecules, including genotoxic PAHs. The CDMSNs were synthesized by the surfactant-templated, NaOH-catalyzed condensation reactions of tetraethyl orthosilicate (TEOS) in the presence of two different types of cyclodextrin (i.e. hydroxypropyl-β-cyclodextrin (HP-β-CD) and native β-cyclodextrin (β-CD)). The physical incorporation of CD moieties was supported by XPS, FT-IR, NMR, TGA and solid-state 13C NMR. The CDMSNs were treated with aqueous solutions of five different PAHs (e.g. pyrene, anthracene, phenanthrene, fluorene and fluoranthene). The functionalization of MSNs with cyclodextrin moieties significantly boosted the sorption capacity (q) of the MSNs up to ∼2-fold, and the q ranged between 0.3 and 1.65 mg per gram CDMSNs, of which the performance was comparable to that of the activated carbon.Item Open Access Intramolecular through-space charge-transfer in naphthalene-based compounds and development of an efficient heterogeneous catalytic method for the aerobic C-H oxidation of alkylarenes(2023-09) Çalıkyılmaz, EylülThe transfer of electrons between two molecules or between different groups attached to a molecule is known as charge transfer. Electronic communication can take place either through chemical bonds or through space. Intramolecular through-space charge transfer occurs between donor and acceptor parts of a molecule depending on the electron density difference, the distance between them, and their relative positions. The main objective of the project is to study the phenomenon of intramolecular through-space charge transfer in naphthalene-based organic materials. We investigated the charge transfer in 1,8-substituted naphthalene derivatives and the effect of different electron-donating and electron-withdrawing groups. To investigate the role of these groups, a variety of control substrates which have different electronic structures were synthesized. Subsequently, it was determined which substances possess a charge transfer band by examining the UV-Vis spectra of these substances. Additionally, it was found that substances with charge transfer bands in UV-Vis absorption spectroscopy had multiple emission values when fluorescence spectra were analyzed. In addition, to observe the effect of different solvents on charge transfer, the substance with observed charge transfer was dissolved in different solvents and examined in terms of color, absorption, and emission values. A key objective of the second part is to develop an environmentally friendly and efficient earth-abundant metal hydroxide catalyst that can be used in aerobic C-H activation reactions for a variety of organic compounds. Metal hydroxides are used for this purpose because of their ability to operate at relatively low temperatures and it allows metal hydroxides to act as highly effective catalysts for oxidation reactions. As an earth-abundant metal-containing catalyst, FexMn(1-x)(OH)y has been prepared by the Özensoy research group with different elemental ratios. In addition, the concentration of NaOH was systematically investigated during the synthesis of the catalyst. The catalytic activities of all catalysts were studied in the aerobic oxidation of fluorene to fluorenone as a model reaction. The optimized conditions were used for the oxidation of diphenylmethane to benzophenone. Subsequently, diphenylmethanes functionalized with electron-donating and electron-withdrawing groups were synthesized, and the yields of oxidation reactions were determined. Finally, the results of the kinetic isotope effect experiment were combined with the yields of the previous experiments to shed light on the mechanism of oxidation.Item Open Access Poly-cyclodextrin cryogels with aligned porous structure for removal of polycyclic aromatic hydrocarbons (PAHs) from water(Elsevier, 2017-08) Topuz, F.; Uyar, TamerCyclodextrins (CDs) are sugar-based cyclic oligosaccharides, which form inclusion complexes with small guest molecules through their hydrophobic cavity. Here we successfully synthesized highly porous poly-cyclodextrin (poly-CD) cryogels, which were produced under cryogenic conditions by the cross-linking of amine-functional CDs with PEG-based diepoxide cross-linker. The poly-CD cryogels showed aligned porous network structures owing to the directional freezing of the matrix, of which the pore size and architecture exposed variations depending on the composition of the reactants. The cryogels were employed for the removal of genotoxic polycyclic aromatic hydrocarbons (PAHs) from aqueous solutions. They reached PAH sorption capacities as high as 1.25 mg PAH per gram cryogel. This high sorption performance is due to interactions between PAHs and the complete swollen network, and thus, is not restricted by interfacial adsorption. Given that the hydrophilic nature of the components, the sorption performance could only be attributed to the inclusion complex formation of CDs with PAH molecules. The poly-CD cryogels could be recycled with an exposure to ethanol and reused without any significant loss in the sorption capacity of PAHs.