Browsing by Author "Hakli, Ö"

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    The Conversion of Low-rank Kilyos Coal to Nitrogeneous Fertilizers
    Hakli, Ö; Dumanli, AG; Nalbant, A; Okyay, F; Yürüm, Y
    The aim of this work is to convert the low-rank Kilyos coal to a material that could be used as a nitrogenous fertilizer. Incorporation of nitrogen into this Kilyos coal was accomplished by oxidative ammoniation, which was a two-step process involving oxidation with nitric acid followed by a treatment by ammonia. The nitrogen content of the raw coal increased from 0.8% to 8.3-9.3% after ammoniation process. Trace element concentrations in the nitro-coal, humic acid, and oxy-ammoniated coal samples were within the acceptable ranges to be used as nitrogenous fertilizer. Therefore the oxy-ammoniated products could be considered as high-value fertilizers.
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    Optical and photovoltaic properties of salicylaldimine-based azo ligands
    Dinçalp, H; Yavuz, S; Hakli, Ö; Zafer, C; Özsoy, C; Durucasu, I; Içli, S
    A series of azo dyes containing salicylaldimine-based ligands as side chains were prepared and characterized. Absorption and emission data in five solvents of different polarities were studied. Photoirradiation studies under an oxygen atmosphere in water showed that the Schiff base side chains enhanced the photo-oxidative stability of the azo chromophore. The electrochemical properties of the dyes were investigated by a cyclic voltammetry. The synthesized salicylaldimine-based azo dyes gave two irreversible oxidation potentials. Complexation behavior of synthesized compounds with titanium (IV) ions was illustrated by the change in their absorption spectra. These ligands are appropriate sensitizers for anchoring to the TiO2 surface chemically in dye-sensitized solar cell (DSSC) productions. Electron injection capacities to TiO2 and photovoltaic performance of the synthesized salicylaidimine-based azo dyes were tested with DSSC. (C) 2009 Elsevier B.V. All rights reserved.
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    A study on photophysical properties of some Vitamin K3 derivatives
    Hakli, Ö; Karapire, C; Posokhov, Y; Içli, S
    Photophysical properties of menadione sodium bisulfite (MSB), menadione nicotinamide bisulfite (MNB) and menadione dimethylpyrimidinol bisulfite (MPB) were studied in their aqueous solutions. They are oil-soluble vitamins and not naturally fluorescent, however, it is possible to gain fluorescent signal by the use of phosphate buffer solutions containing sodium dodecyl sulfate (SDS) at optimum concentration. The quantum yields of fluorescence emission, Phi(f), were measured as similar to10(-4), 0.0085 and 0.053 for MSB, MNB, MPB, respectively. Fluorescence quenching with Co2+ ions yielded the quenching rates of 1.7 x 10(9), 4.6 x 10(10), and 1.5 x 10(10) M-1 s(-1) for MSB, MNB and MPB, respectively. Calculated Gibbs free energy (DeltaG) values (less than or equal to-5 kcal/mol) of the compounds suggest that electron transfer could be the reason of quenching with Co2+ ions. Studied derivatives were found to give two electrons. Equilibrium constants (K-eq) derived from DeltaG values pointed out strong association between the pairs of MSB, MNB and MPB complexes. They were irradiated by using not only artificial Xe lamp of fluorescence spectrophotometer, but also by using direct and concentrated sunlight and degradation (%), rate constant (k(p)) and half-lives (t(1/2)) were compared. Photodegradation (%) of Vitamin K-3 derivatives varied depending on the irradiation source. Photostability tests pointed out MPB as the most stable derivative. (C) 2004 Elsevier B.V. All rights reserved.