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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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    Hydrogel templated CdS quantum dots synthesis and their characterization
    (Elsevier, 2011) Şahiner, Nurettin; Sel, Kıvanç; Meral, Kadem; Onganer, Yavuz; Bütün, Sultan; Özay, Özgür; Sılan, Coşkun
    This work reports a facile method for preparation of CdS quantum dots (Q-dots), using a crosslinked hydrophilic p(AMPS) hydrogel network by absorption of Cd(II) ions and sequential precipitation with aqueous Na2S within the network at room temperature. The TEM images revealed that prepared CdS Q-dots were distributed throughout the p(AMPS) hydrogel network and their sizes were about 5 nm. The amount of inorganic material inside p(AMPS) hydrogel was determined by TGA measurements to be 16.9% by weight. Additionally, the Cd and S amounts inside the p(AMPS) network were determined by dissolution of particles with HCl (three treatments with 3 M HCl) and by using ICP-AES (for Cd) and an elemental analyzer (for S). From UV-visible absorbance measurements, optical energy gap values of 5.1 +/- 0.1 eV for p(AMPS) and 2.4 +/- 0.05 eV for p(AMPS)-CdS were determined. From the fluorescence spectrum of the p(AMPS)-CdS hydrogel, the peak energy was observed at 2.30 eV. The in situ prepared Q-dots were recovered from hydrogel matrices by placing the p(AMPS)-CdS composite in purified water. (C) 2011 Elsevier B.V. All rights reserved.