Chemical Engineering / Kimya Mühendisliği

Permanent URI for this collectionhttps://hdl.handle.net/11147/14

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Author: search.filters.author.Şen, Selin

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  • Article
    Citation - WoS: 3
    Citation - Scopus: 4
    Photocatalytic and Optical Properties of Zinc Oxide Structures Prepared at Different Urea Concentrations
    (Serban Solacolu Foundation, 2020) Uysal, Berk; Şen, Selin; Top, Ayben
    In this study, ZnO samples were synthesized using zinc acetate and urea with a method containing sonication, sol-gel transition and calcination steps. Urea to zinc acetate mole ratio values were changed as 0, 0.5, 1, and 2 and corresponding calcined samples were denoted as UZ-0, UZ-0.5, UZ-1, and UZ-2, respectively. Scanning electron microscopy (SEM) images indicated globular and rod-like structures. Aspect ratios of the nanorods increased as urea to zinc acetate ratio increased from 0 to 1 whereas nanoparticles with sizes of 70 +/- 20 nm were observed for UZ-2 sample. Brunauer, Emmett and Teller (BET) surface area values of the samples varied between 9 and 25 m(2)/g and increased as initial urea amount increased. Band gap energies of the samples ranged between 3.24 and 3.29 eV. Four major peaks at about 400, 420, 480 and 530 nm with different intensities were observed in the photoluminescence (PL) spectra of the samples. All the samples removed rhodamine B by both adsorption and photodegradation. The highest visible light induced photodegradation rate was exhibited by UZ-2 sample having the highest surface area and it is attributed to superior charge separation properties of this sample under visible light.
  • Article
    Citation - WoS: 1
    Citation - Scopus: 1
    Potansiyel Doksorubisin Taşıyıcı Sistemi Olarak Peg-endozom Parçalayıcı Peptit Konjugatının Değerlendirilmesi
    (Gazi Üniversitesi, 2020) Şen, Selin; Top, Ayben
    In this study, it was aimed to develop a doxorubicin (DOX) carrier system based on a PEGylated TAT-derived cell penetrating peptide (G(2)RQR(3)QR(3)G(2)S) and to investigate drug release, self-assembly and stability properties of the carrier system. In the preparation of the drug delivery system, denoted as mPEG-peptide-oxime-DOX, methoxypolyethylene glycol (mPEG) with M-n=1900 Da was used. DOX was attached to the mPEG-peptide carrier system via acid cleavable oxime bond. Control drug delivery system, lack of the peptide (mPEG-oxime-DOX) was also synthesized to assess the effect of the peptide on the physicochemical and DOX release properties of the carrier system. mPEG-oxime-DOX exhibited a pH programmed DOX release with respective % DOX release values of similar to 68% and similar to 28% at pH 5.0 and at pH 7.4 at the end of 54 h. For the mPEG-peptide-oxime-DOX, on the other hand, quite low DOX release (similar to 10-15 %) was observed for both pH values suggesting possible interactions between DOX and the peptide. Initial median size value (D50) of the mPEG-oxime-DOX was measured as similar to 24 nm, independent of pH. However, for the mPEG-peptide-oxime-DOX, quite lower D50 values (similar to 3 nm and similar to 6 nm at pH 5.0 and pH 7.4, respectively) were obtained due to the repulsions between the arginines in the peptide sequence. Sizes of both drug delivery systems, tended to increase upon incubation at physiological conditions for 1 day suggesting that longer PEG chains should be used to enhance the stability of the mPEG-peptide-oxime-DOX and mPEG-oximeDOX systems.
  • Article
    Citation - WoS: 4
    Citation - Scopus: 4
    Optical and Photocatalytic Properties of Zno and Zns Structures Formed as Controlled Calcination Products of L-Cysteine Assisted Aqueous Precipitation
    (Elsevier, 2020) Şen, Selin; Top, Ayben
    ZnO and ZnS structures were obtained by the calcination of the aqueous precipitation products of Zn(NO3)2, NaOH and L-cysteine (Cys). Initial Cys:Zn molar ratios were changed as 0.1:1, 0.5:1, 1:1 and 1.5:1. All the precursors were transformed into ZnO upon calcination at 700 °C. ZnS structures were obtained by calcining the precursors prepared at the Cys:Zn ratios of 1 and 1.5 at 350 °C. In addition to changing chemical composition of the precipitation products, calcination temperature and initial Cys:Zn ratio also affected morphology, surface area, photoluminescence and photocatalytic properties of the final products. Free exciton energy values of the ZnO samples were observed to be between 3.29 eV and 3.35 eV. PL spectra of the ZnO samples indicated blue and green emission centers. Zinc interstitials (Zni), revealed by the blue emissions in the PL spectra were also confirmed by Auger Zn L3M4.5M4.5 spectra. The samples calcined at 350 °C removed rhodamine B mainly by adsorption. All the samples calcined at 700 °C successfully degraded the dye under UV light. Among the samples calcined at 700 °C, ZnO sample prepared at Cys:Zn = 0.5, which has the highest surface area and unique photoluminescence spectrum exhibited the fastest photodegradation rate. © 2020 Elsevier Ltd