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    Environmentally-friendly preparation of chitosan microspheres and encapsulation studies of cinnamaldehyde: ?owards convenient sustained release system for cinnamaldehyde
    (Macedonian Journal of Chemistry and Chemical Engineering, 2021) Yeldir, Elif Karacan; Oral, Ayhan
    Chitosan, a biodegradable and biocompatible polysaccharide, is a biopolymer with high potential for biomedical applications. In the scope of this study, chitosan microcapsules were prepared via a green method, without using any surfactants or crosslinkers. Cinnamaldehyde encapsulated microspheres were obtained by the same method and characterized by FTIR spectroscopy, XRD spectroscopy, and SEM. The release study of encapsulated cinnamaldehyde was carried out in a pH 7.4 phosphate buffered saline (PBS) at 37 °C. The amount of cinnamaldehyde released was analyzed using UV-Vis spectroscopy and GC/MS-MS. Accordingly, it was found that 350 mg of cinnamaldehyde was encapsulated per gram of chitosan, and the maximum amount of cinnamaldehyde released into the PBS medium was about 8 ppm. In addition, the release was seen to continue when the buffer was renewed. It is thought that the obtained cinnamaldehyde encapsulated chitosan microspheres could be used as a sustained release system.
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    Synthesis of Poly(azomethine) Containing Sulfonic Acid Unit Oxygen and Sulphur Bridged: Investigation of Its Thermal, Optical and Electrochemical Properties
    (2022) Yeldir, Elif Karacan
    In this study, a poly(azomethine) compound (SBP) containing sulfur and oxygen bridge was obtained from 4,4'-[thiobis(4,1-phenyleneoxy)]dibenzaldehyde (DBA)and 4,4'diamino-2,2'-biphenyl sulfonic acid from condensation reaction. Structural, optical, electrochemical and morphological analyzes of the obtained polymeric material were performed. Structural characterizations were performed from 1H-NMR and FT-IR spectra. Optical properties were determined in the UV-Vis spectrum and the optical band gap was calculated as 3.63 eV. Electrochemical properties were investigated by cyclic voltammetry (CV) and HOMO-LUMO and electrochemical band gap values were calculated. In addition, with the help of Gel Permeation Chromatography (GPC), the number average molecular mass was found to be 5050 Da. By thermogravimetric analysis (TGA), it was found that the thermal decomposition of SBP occurred in four steps and the maximum mass loss was 391 °C. The surface analysis of the obtained polymeric material was investigated with scanning electron microscope (SEM) and it was determined that the surface was rough.
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    Synthesis, characterization, and investigation of some properties of the new symmetrical bisimine Ni(II), Zn(II), and Fe(III) complexes derived from the monoimine ligand
    (Wiley, 2021) Portakal, Eylem Dilmen; Kaya, Yeliz; Demirayak, Emire; Yeldir, Elif Karacan; Ercağ, Ayşe; Kaya, İsmet
    The new symmetrical bisimine (ONNO donor, salen type) Ni(II), Zn(II), andFe(III) complexes were synthesized in one step from metal ions and mon-oimine ligand (HL: 4-amino-3-{[(2-hydroxynaphthalen-1-yl)methylidene]amino}phenyl)(phenyl)methanone). The complexes were characterized by ana-lytical, spectral, conductance, magnetic, and thermal data. According to theseanalysis results, while the bisimine ligand, spontaneously forming during com-plexation, is attached to the metal by two nitrogen atoms and two phenolicoxygen atoms (N2O2) in all complexes, in the Fe(III) complex, the fifth coordi-nation is completed by the chlorine molecule. A square pyramidal geometryfor [FeLCl] and a square planar geometry for [NiL], [ZnL] were proposed. Thethree-dimensional structure of [FeLC1] was also evaluated by single-crystal X-ray diffraction, and the square pyramidal structure was clearly revealed. Themolar conductivity data of the complexes confirmed their nonelectrolyticnature. Poly(imine) (PL) was obtained by the oxidative polymerization reactionof HL, and some of its properties were investigated. The electrochemical prop-erties of the ligand and the complexes were studied by means of cyclicvoltammetry. Highest and lowest occupied molecular orbital (HOMO-LUMO)energy levels and electrochemical band gaps were calculated. The ther-mogravimetric analysis (TGA) and differential thermal analysis (DTA) of thesynthesized compounds were carried out. TGA results showed that the thermalstability of the complexes is high. The solid-state electrical conductivities of theiodine doped states of the synthesized compounds were measured by the four-point probe technique. PL has approximately 35 times higher electrical con-ductivity than the HL and complexes. Fluorescence-sensor properties of HLwere also investigated and predicted that HL could be a selective fluorescenceprobe for Pb2+