Yazar "Ozdokur, Kemal Volkan" seçeneğine göre listele

Listeleniyor 1 - 3 / 3
  • [ X ]
    Öğe
    A novel amperometric H2O2 biosensor constructed by cress peroxidase entrapped on BiFeO3 nanoparticles
    (Elsevier Science Sa, 2021) Caglar, Bulent; Icer, Fatih; Ozdokur, Kemal Volkan; Caglar, Sema; Ozdemir, Agah Oktay; Guner, Eda Keles; Beser, Burcu Meryem
    Herein, we synthesized ferromagnetic BiFeO3 nanoparticles with sizes of 20-60 nm and rhombohedral distorted perovskite structure without any co-formed impurity phases by sol-gel method. Structural, morphological, magnetic, electronic and textural properties of BiFeO3 nanoparticles were characterized by using XRD, SEM-EDX, TEM, FTIR, XPS, VSM, UV-DRS, PL and BET techniques. The peroxidase was isolated from the Cress (Lepidium sativum) and purified by using precipitation of ammonium sulfate and chromatographic techniques; gel filtration and ion exchange chromatography which is showed wide range of thermal stability, maximum activity in the acidic environment and close to the body temperature. Afterwards, a novel amperometric biosensor based on Cress peroxidase entrapped on BiFeO3 nanoparticles modified carbon paste electrode was prepared for the first time to sensitive detection of H2O2. The prepared H2O2 biosensor was operated with the aid of chomamperometry technique by applying -0.8 V vs Ag/AgCl electrode. The developed biosensor exhibited a linear response towards to H2O2 in the concentration range of 2.0 10(-7) to 1.0 10(-5) M under the optimal conditions and limit of detection and quantification were estimated as 7.0 10(-8)M (2.7 mu g L-1) and 2.0 10(-7) M (8.7 mu g L-1), respectively. The repeatability of the electrode was calculated as 19.2 for 2.0 10(-7) M (N = 7) and the accuracy was 81.2% for this concentration. In addition, the H2O2 biosensor exhibited excellent stability up to ten days. Finally, the sensor developed was used for the analysis of H2O2 in milk samples and satisfactory recoveries were obtained under the operating conditions.
  • [ X ]
    Öğe
    Application of BiFeO3 and Au/BiFeO3 decorated kaolinite nanocomposites as efficient photocatalyst for degradation of dye and electrocatalyst for oxygen reduction reaction
    (Elsevier Science Sa, 2021) Caglar, Bulent; Guner, Eda Keles; Ozdokur, Kemal Volkan; Ozdemir, Agah Oktay; Icer, Fatih; Caglar, Sema; Dogan, Bilge
    To improve the photocatalytic performance and solve the aggregation problem of BiFeO3 nanoparticles, kaolinite-BiFeO3 photocatalyst was successfully prepared for the first time by decoration of ferromagnetic BiFeO3 nanoparticles onto kaolinite surface. Comparative characteristics of kaolinite, bare BiFeO3 and kaolinite-BiFeO3 photocatalyst were investigated in detail by XRD, TEM, SEM-EDX, XPS, FTIR, VSM, UV-DRS, PL, zeta potential and BET techniques. The photocatalytic activities of the samples were also evaluated by photodegradation of rhodamine B as a model reaction under different irradiations like UVA, visible and sunlight. The kaolinite-BiFeO3 exhibited more superior photocatalytic activity as compared with other samples, which is best fitted to pseudofirst-order kinetic. The reactive species trapping experiments indicated that photogenerated-holes play major roles in the degradation process whereas superoxide radicals possess a secondary effect. Enhanced photocatalytic activity of kaolinite-BiFeO3 is attributed to its kaolinite platform that reduces the recombination opportunities of the photogenerated holes and electrons as well as increases the surface area, decreases the particle size and aggregation of nanoparticles. In addition, we also designed a novel electrocatalytic platform based on gold nanoparticles loaded on kaolinite-BiFeO3 modified carbon paste electrode surface for the examination of electrocatalytic activity for oxygen reduction reaction in alkaline medium. Electrochemical characterizations of the Au/BiFeO3/kaolinite modified carbon paste electrode and other bare surfaces were comparatively carried out with the aid of cyclic voltammetry, electrochemical impedance spectroscopy and chronoamperometry. Au/ BiFeO3/kaolinite modified carbon paste electrode exhibited 15-fold current enhancement together with 100 mV anodic potential shift compared with bare carbon paste electrode.
  • [ X ]
    Öğe
    Fe3O4 nanoparticles decorated smectite nanocomposite: Characterization, photocatalytic and electrocatalytic activities
    (Elsevier Science Bv, 2018) Caglar, Bulent; Guner, Eda Keles; Keles, Kubra; Ozdokur, Kemal Volkan; Cubuk, Osman; Coldur, Fatih; Caglar, Sema
    Magnetite nanoparticles-decorated smectite nanocomposite was prepared by precipitation method and the obtained nanocomposite was used as both nanophotocatalyst for removal of rhodamine B from wastewater under UVA irradiation and electrocatalyst for the electrooxidation of chlorite ion on the carbon paste electrode. The raw smectite, bare magnetite and the synthesized nanocomposite catalyst were comparatively characterized by using XRD, FTIR, SEM, EDX, XPS, VSM, TG/DTG, DTA, DSC, electrophoretic mobility and BET techniques in detail. The XRD, SEM, electrophoretic mobility and VSM results indicated that the magnetite nanoparticles were uniformly distributed on the surface of smectite with a diameter of about 7 nm by electrostatic interactions and the prepared nanocomposite displayed well superparamagnetic behaviour with strong saturation magnetization at room temperature. The XPS, EDX, FTIR and thermal analysis data of synthesized nanocomposite further confirmed that the magnetite nanoparticles were successfully decorated on the smectite without formation of another ferric phase species. Furthermore, the surface area of magnetite smectite nanocomposite is higher than that of raw smectite, which is related to the magnetite nanoparticles decorated onto the smectite. The catalytic activities of all samples were comparatively investigated by using the degradation of aqueous rhodamine B solutions as a model pollutant in the heterogeneous photo-like-Fenton process which is well defined by the pseudo-first-order equation in kinetics. The resultant magnetite-smectite nanocomposite showed excellent magnetic separability and much better photocatalytic activity in a short period compared to the bare magnetite and smectite. The synergetic effect between magnetite and smectite showed high activity not only in photo-degradation but also in electrocatalytic applications. Because the developed nanocomposite material exhibited enhanced catalytic activity towards to chlorite ion oxidation it was applied for the voltammetric quantification of chlorite ion in aqueous medium. After the optimization of the measurement parameters, the limit of detection and quantification of the method were calculated as 3.0 and 10.0 mu M, respectively.