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    Gum Arabic Microgels As Template for In Situ Metal-Sulfide Based Quantum Dots Preparation and Their Thermal, Spectroscopic, Optical, and Magnetic Characterization
    (Springer, 2017) Farooq, Muhammad; Sağbaş, Selin; Yıldız, Mustafa; Meral, Kadem; Siddiq, Mohammad; Aktaş, Nahit; Şahiner, Nurettin
    Here, gum arabic (GA) microgel in 5-50 mu m size range was used as a template for in situ quantum dot (QD) preparation. The in situ synthesis of metal sulfide quantum dots (QDs) such as CdS, PbS, CuS, ZnS, CoS, and MnS was accomplished by the absorption of the corresponding metal ions from aqueous solutions and then in situ precipitation with S2- treatments within GA microgels. Transmission electron microscopy (TEM) confirmed the existence of the evenly distributed QDs within GA microgel matrices for each of the prepared QDs. All the fabricated GA-QD composites have shown excellent semiconducting behaviors with relatively larger band gap values of 4.87 eV, 4.60 eV, 6.71 eV, 4.81 eV, 3.68 eV, 5.2 eV, and 4.0 eV for CdS, PbS, ZnS, CuS, CoS, MoS, and MnS, respectively. The results revealed that CdS and ZnS are found to be the most efficient florescence materials amongst the all QDs with 630 and 70 cd/cm(2) fluorescence intensities, respectively. Moreover, the magnetic susceptibility study suggests that Mn(IV), Co(III), and Mo(IV), have mononuclear octahedral geometries whereas Zn(II), Cd(II), and Pb(II) show binuclear geometries.
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    Synthesis, characterization and modification of Gum Arabic microgels for hemocompatibility and antimicrobial studies
    (Elsevier Sci Ltd, 2017) Farooq, Muhammad; Sağbaş, Selin; Şahiner, Mehtap; Siddiq, Mohammad; Türk, Mustafa; Aktaş, Nahit; Şahiner, Nurettin
    Gum Arabic (GA) microgels were successfully prepared via reverse micellization method with high yield (78.5 +/- 5.0%) in 5-100 mu m size range using divinyl sulfone (DVS) as a crosslinker. The GA microgels were degraded hydrolytically 22.8 +/- 3.5% at pH 1 in 20 days, whereas no degradation was observed at pH 7.4 and pH 9 at 37 degrees C. By using diethylenetriamine (DETA), and taurine (TA) as chemical modifying agents, GA microgels were chemically modified as GA-DETA and GA-TA, and the zeta potential values of 5.2 +/- 4.1 and -24.8 +/- 1.3 mV were measured, respectively in comparison to -27.3 +/- 4.2 mV for GA. Moreover, blood compatibility of GA, GA-TA, and GA-DETA microgels was tested via in vitro protein adsorption, % hemolysis ratio, and blood clotting index. All the microgels were hemocompatible with% hemolysis ratio between 0.23 to 2.05, and the GA microgels were found to be highly compatible with a blood clotting index of 81 +/- 40. The biocompatibility of GA, GA-DETA and GA-Taurine microgels against L929 fibroblast cells also revealed 84.4, 89.1, and 67.0% cell viability, respectively, at 25.0 mu g/mL concentration, suggesting great potential in vivo biomedical applications up to this concentration. In addition, 5 and 10 mgImL minimum inhibition concentrations of protonated GA-DETA microgels (GA-DETA-HCl) were determined against E. coli and S. aureus, respectively. (C) 2016 Elsevier Ltd. All rights reserved.
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    Synthesis, Characterization, and Use of Carbon Microspheres for Removal of Different Dyes from Aqueous Environments
    (Springer, 2017) Şahiner, Nurettin; Farooq, Muhammad; Rehman, Saif Ur; Sağbaş, Selin; Şahiner, Mehtap; Siddiq, Mohammad; Aktaş, Nahit
    Herein, we report the synthesis of carbon spheres (CS) using a relatively low-temperature hydrothermal technique using lactose as precursor pre-treated with HCl. The successful synthesis, spherical morphology, porous morphology, and monodispersed nature of CS were confirmed via scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Isoelectric point (IEP) was determined as 3.8, and at neutral conditions the prepared carbon particles are negatively charged at - 43 +/- 2.50 mV. Owing to their spherical morphology, almost uniform distribution and negatively charged surface at neutral conditions, the prepared CS were used as adsorbent for the removal of methylene blue (MB) and Geimsa stain (GS) from aqueous environments at pH 7. It was shown that CS has 97% adsorption capability for GS, whereas for methylene MB, the maximum adsorption capacity was 67% for 0.1-g CS from 50-ppm dye solutions in DI water. The adsorption studies revealed that the Langmuir and modified Fruendlich (MFE) adsorption models resulted in considerably high linear correlation coefficient (r(2)) values and the efficient adsorption of positively charged species on CS can be represented better with the MFE model.