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    Effect of pH on Optic and Structural Characterization of Chemical Deposited AgI Thin Films
    (Univ Fed Sao Carlos, Dept Engenharia Materials, 2017) Tezel, Fatma Meydaneri; Kariper, Ishak Afsin
    AgI thin films were grown on amorphous commercial glass substrates with chemical bath deposition (CBD) at different pH values (2, 3, 4, 5, 6), 6 hours deposition time and 60 degrees C. The structure of the nanocrystals was characterized by X-ray diffraction (XRD). The ratio of Ag+ and I-ions changed the crystalline structures. The presence of the Ag+ ions produces the.-phase of AgI and excess of iodine concentration produces beta-phase of AgI. The pH: 4 was like a transition pH for these phases. The number of crystallites per unit area has maximum value at pH: 5, as the structure is re-crystallization to hexagonal phase. Also, the thicknesses of produced thin films were decreased with increased pH values. Therefore, transmission, reflection, extinction coefficients and refractive index of the materials were affected by thicknesses, and calculated to be 32, 35, 3, 11, 9 (%) - 27, 25, 61, 45, 49 (%) - 0.036, 0.032, 0.067, 0.107, 0.075 and 3.21, 3.02, 5.16, 8.35, 5.70 in 550 nm at pH: 2-3-4-5-6 values, respectively. The exciton peaks of AgI were observed at between 320 and 420 nm. Surface properties were investigated by using scanning electron microscopy (SEM).
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    Effects of pH on the optical, structural and supercapacitive properties of BiTe thin films produced via CBD
    (Indian Acad Sciences, 2021) Tezel, Necmi Serkan; Tezel, Fatma Meydaneri; Kariper, Ishak Afsin
    In this study, BiTe thin films are grown on glass substrates by chemical bath deposition method, at different pH levels. Crystallographic structures, crystal dimensions, dislocation densities and crystallization numbers of thin films are characterized by X-ray diffraction, whereas surface morphologies, roughness and film thicknesses are characterized by scanning electronic microscopy and atomic force microscopy. Surface tensions are calculated by Zisman method using different liquids. Capacitance, energy and power densities are calculated for each pH level by using time-dependent current-voltage measurements. Monocrystalline thin films of Bi2Te3 are observed at pH 3 and Bi4Te5 at pH 11, whereas polycrystalline Bi2Te3 and Bi4Te5 structures are formed at pH 7 and 9, respectively. Surface roughness and film thicknesses of polycrystalline thin films are found to be significantly higher than monocrystalline thin films. Capacitance, energy and power density of BiTe thin films produced at pH 3, 7, 9 and 11 are calculated as 503, 562, 569 and 512 F g(-1); 55.19, 61.66, 62.43 and 56.17 Wh kg(-1); and 3311.4, 3699.6, 3745.8 and 3370.2 W kg(-1), respectively. These results show that capacitance, energy and power density of polycrystalline thin films produced at pH 7 and 9, which have high surface load activity, are higher. Electrical resistivity of Bi2Te3 and Bi4Te5 monocrystalline films are lower than those of the polycrystalline BiTe films.
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    High energy supercapacitors based on functionalized carbon nanotubes: Effect of atomic oxygen doping via various radiation sources
    (Elsevier Sci Ltd, 2022) Kariper, Ishak Afsin; Korkmaz, Satiye; Karaman, Ceren; Karaman, Onur
    Herein, carbon nanotubes (CNTs) were oxygen functionalized by irradiation with diverse radiation sources including Am-241, Sr-90, Co-60, and Na-22 for the first time to be used as the electrode material in a high-energy supercapacitor. The oxygen contents of the irradiated CNTs were fine-tuned via the energy of the radiation source. The physicochemical characterization of as-obtained CNTs was conducted by X-Ray Diffraction (XRD), Raman, and Scanning Electron Microscopy, Energy Dispersive X-Ray (SEM-EDX) analysis whereas cyclic voltammetry and galvanostatic charge-discharge techniques were performed to assess the electrochemical performance of the as-assembled symmetrical supercapacitor cells. The CNT irradiated by Am-241 radiation source offered superior specific capacitance values compared to the other irradiated CNTs thanks to its higher content of oxygen functional groups. The highest specific capacitance for CNT Am-241 sample (with 7.32% oxygen) was calculated to be 489.6 F.g(-1) at a current density of 0.1 A.g(-1), which was almost 2.75 fold that of non-irradiated CNT sample. The capacitance retention of as-synthesized CNT Am-241 was determined as 98.50% for the 5,000th CV cycle. The outstanding energy density of 56.90 W.h.kg(-1) was achieved even at a high power density value of 9992.19 W.kg(-1), comparable to the commercial batteries, will pave the way for facile fabrication of high-energy electrochemical energy storage systems based on functionalized carbon nanotubes.
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    MWCNT/Ruthenium hydroxide aerogel supercapacitor production and investigation of electrochemical performances
    (Nature Portfolio, 2022) Korkmaz, Satiye; Kariper, Ishak Afsin; Karaman, Ceren; Karaman, Onur
    In this study, the material obtained from the sonication of the double-walled carbon nanotube and ruthenium chloride was produced as an aerogel. Then, symmetrical supercapacitor devices were made using them, and their electrochemical properties were investigated. XRD and FTIR were used in the structural analysis of the aerogel, STEM in surface images, and elemental analyses in EDX. Electrochemical analysis was performed by galvanostat/potentiostat. From the cyclic voltammetry analysis, the highest specific capacitance for MWCNT/Ruthenium hydroxide aerogels was achieved as 423 F/g at 5 mV/s. On the other hand, the corresponding values calculated from the charge-discharge curves were found to be 420.3 F/g and 319.9 F/g at the current densities of 0.5 A/g and 10.0 A/g, respectively. The capacitance retention of as-synthesized aerogel was 96.38% at the end of the 5000 consecutive consecutive cyclic voltammetry cycles.
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    Structural, surface, optical, and antimicrobial characterization of I2/Polymethyl methacrylate and CuS/I2/polymethyl methacrylate thin films
    (Elsevier, 2022) Tezel, Fatma Meydaneri; Kariper, Ishak Afsin; Kaan, Dilek; Bahar, Dilek
    In this study, I2/PMMA and CuS/I2/PMMA thin films were produced by Chemical Bath Deposition (CBD) on polymethyl methacrylate (PMMA) substrates, and their physicochemical and antimicrobial properties were analyzed. The film's surface tensions were characterized by KSV instruments, and the surface tensions for plain PMMA, I2/PMMA, and CuS/I2/PMMA thin films were 30.27, 28.77, and 31.86 mN/m, respectively. The I2 and CuS/I2 structures in the XRD patterns are amorphous. After coating CuS, the long rod-like extension structures are formed; spherical shapes form some agglomeration in some regions to SEM images. Chemical analysis was performed with an EDX spectrometer attached to SEM. The thicknesses and surface roughnesses of I2/PMMA and CuS/I2/PMMA thin films were determined to be 50.34 nm, 1126 nm; 62.03 nm and 204.99 nm via AFM, respectively. The optical spectra of the films were recorded in the range of 300-1100 nm with a UV-VIS spec-trophotometer. The antibacterial and antifungal properties of I2 and CuS coating were evaluated against facul-tative gram-negative E. Coli and C. Albicans. The coated films exhibited excellent antimicrobial performance.