Sürdürülebilir Kalkınma Amaçları
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- ArticleAçık Erişim2021A novel amperometric H2O2 biosensor constructed by cress peroxidase entrapped on BiFeO3 nanoparticles
Caglar, Bulent; İçer, Fatih; Özdokur, Kemal Volkan; Caglar, Sema; Özdemir, Agah Oktay; Guner, Eda Keles; Beşer, Burcu Meryem; Altay, Ahmet; Çırak, Çağrı; Doğan, Bilge
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 choro-amperometry 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 μg L−1) and 2.0 10−7 M (8.7 μg 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.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2021Application of BiFeO3 and Au/BiFeO3 decorated kaolinite nanocomposites as efficient photocatalyst for degradation of dye and electrocatalyst for oxygen reduction reaction
Caglar, Bulent; Guner, Eda Keles; Özdokur, Kemal Volkan; Özdemir, Agah Oktay; İçer, Fatih; Caglar, Sema; Doğan, Bilge; Beşer, Burcu Meryem; Çırak, Çağrı; Tabak, Ahmet
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 pseudo-first-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.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2021TRINUCLEAR SILVER(I) COMPLEX OF NON-STEROIDAL ANTI-INFLAMMATORY DRUG NAPROXEN: SYNTHESIS, CHARACTERIZATION, AND IN VITRO CYTOTOXICITY
Caglar, Sema; Altay, Ahmet; Harurluoğlu, Betül; Caglar, Bulent
Herein, a new silver(I) complex with the non-steroidal anti-inflammatory drug naproxen and nitrogen donor 3-picoline ligands was synthesized, characterized, and subsequently tested for its cytotoxicity against different types of cancer cell lines. Elemental analysis, Fourier transform infrared spectroscopy, thermal, and proton nuclear magnetic resonance techniques showed that the molecular formula of the prepared complex is bis(3-picoline)tris(μ-naproxenato)trisilver(I) and naproxen ligands bind to silver ions in a bridging bidentate mode. 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) results revealed that silver salts and naproxen alone showed quite weak cytotoxic activity against human breast adenocarcinoma (MDA-MB-453), lung adenocarcinoma (A-549), and colorectal adenocarcinoma (HT-29) cell lines (IC50 > 250 µM), whereas the complex displayed dose dependent cytotoxicity against the aforementioned cell lines. The highest cytotoxicity was observed on MDA-MB-453 cells with an IC50 value of 11.73 µM. Moreover, the complex showed higher selectivity against the cancer cell lines compared to fibroblast 3T3-L1 cells. This study provides preliminary scientific data on the complex for further elucidation of its anticancer mechanism of action.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2020Characterization of Various Cation Exchanged and Pillared Artvin Bentonites and Their Use as a Catalyst in a Selected Organic Reaction
Kaya, Mehmet; Caglar, Bulent; Tabak, Ahmet
In this study, the catalytic activities of raw, some metal cations exchanged (Fe3+ and Cu2+) and Fe- and Alpillared Artvin bentonite samples as a catalyst for acetalization reaction of benzaldehyde with 2, 3-butanediol were investigated. The structural and physicochemical properties of clay samples were examined by using XRay powder diffraction (XRD), scanning electron microscope (SEM), Fourier Transform infrared (FTIR) and surface area measurement techniques. The yield of this organic reaction in the presence of Cu-bentonite and Alpillared bentonites were found as very low whereas Fe-bentonite and Fe-pillared bentonite catalysts showed 60 and 63% yield in acetalization under same conditions, respectively. This study showed that modified Artvin bentonite samples which is the one member of Turkey’s important local and natural sources can be used as catalyst in the selected organic reaction and their utilization in industrial process reactions in small scale.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2020CuxZn(1-x)O Nanoparçacıklarıyla Dekore Edilmiş Kaolin Nanokompozitinin Sentezi, Karakterizasyonu ve Fotokatalitik Aktivitesi
Caglar, Bulent; Güner, Eda Keles
Kaolin yüzeyine CuxZn(1-x)O nanoparçacıkları dekore edilerek kaolin-CuxZn(1-x)O nanokompoziti hazırlandı. Saf kaolinin, saf CuxZn(1-x)O nanoparçacıkları ve hazırlanan bu kaolin-CuxZn(1-x)O nanokompozitin fotokatalitik aktiviteleri UVA ışınları altında Rodamin B boyar maddesinin fotokatalitik bozunması incelenerek değerlendirildi. Bütün numuneler SEM-EDX, XRD, FTIR, ve termik analiz (TG / DTG, DTA) teknikleri kullanılarak karakterize edildi. SEM-EDX ve XRD verileri saf CuxZn(1-x)O nanooksitlerin hekzagonal wurtzite yapısında kristallenmiş ve ZnO’in kristal örgüsünün içerisine bakır iyonlarının girmesiyle genişliği 100-250 nm arası çubuk ve içi boş tüp benzeri nanoyapıların oluştuğunu göstermiştir. Kaolin-CuxZn(1-x)O nanokompozitinde de bu metal oksit nanoyapıların aynı kristal ve morfolojide kaolinin tabakaları arasına sızmadan sadece kilin yüzeyinde dekore olduğu tespit edilmiştir. Kaolin ve CuxZn(1-x)O nanoparçacıkları arasındaki sinerjik etkiden ötürü en iyi fotokatalitik bozunma aktivitesine kaolin- CuxZn(1-x)O nanokompozitinin sahip olduğu ve bozunmanın yalancı birinci dereceden kinetik izlediği belirlendi. Ayrıca bu fotokatalitik bozunmaya ait optimum pH ve katalizör miktarı değerleri tespit edildi.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2020The enhanced light harvesting performance of dye-sensitized solar cells based on ZnO nanorod-TiO2 nanotube hybrid photoanodes
Bozkurt Çırak, Burcu; Eden, Çiğdem; Erdoğan, Yaşar; Demir, Zeynep; Özdokur, K. Volkan; Caglar, Bulent; Morkoç Karadeniz, Sibel; Kılınç, Tuba; Ercan Ekinci, Ali; Çırak, Çağrı
In this study, TiO2/ZnO hybrid nanocomposites (TZ) were fabricated by two step synthesis route for potential applications as photoanode in dye sensitized solar cells (DSSC). Titania nanotubes were grown on titanium sheets by electrochemical oxidation. ZnO nanorods were decorated with hydrothermal method by equimolar (0.1 M) precursors on TiO2 nanotubes. Hydrothermal temperatures values were changed to find the optimal ZnO decoration density to increase photo conversion efficiency. The characterization of the photoanodes was made using FE-SEM, XRD and XPS techniques. The results show that hydrothermal reaction temperature can dramatically enhance the light harvesting performance of TZ photoanodes. The photo conversation efficiency of DSSC by TZ photoanode was reached 1.67 % for hydrothermal temperature of 130 °C which is twofold higher than that of DSSC by TiO2 nanotubes (0.81 %). The improvement in photo conversation conversion efficiency can be assigned to synergetic effect in TZ photoanode, lower recombination rate and charge transfer resistance.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2019Novel Copper(II)-Selective Potentiometric Sensor Based on a Folic Acid-Functionalized Carbon Nanotube Material
Topcu, Cihan; Caglar, Bulent; Guner, Eda Keles; Coldur, Fatih; Caglar, Sema; Yıldırım, Özden; Volkan Özdokur, Kemal; Cubuk, Osman
A folic acid-functionalized carbon nanotube nanomaterial was prepared by immobilizing folic acid molecules on the carbon nanotubes through covalent bonds. The material was characterized using Fourier transform infrared spectroscopy, energy-dispersive X-ray spectroscopy and scanning electron microscopy. Fourier transform infrared spectroscopy confirmed that folic acid molecules were grafted on the carbon nanotube surfaces through the amide bonds between the carboxylic acid functional groups of the oxidized carbon nanotubes and the amine groups of the folic acid molecules. The folic acid molecules bonded to carbon nanotube surfaces led to appreciable changes in the morphology. By using currently obtained folic acid-functionalized carbon nanotube nanomaterial as electroactive material in a polyvinyl chloride membrane, a potentiometric copper (II)-selective sensor was developed. Membrane optimization studies showed that the composition exhibiting the best potentiometric properties was 4.0% (w/w) folic acid–carbon nanotube, 64.0% (w/w) o-nitrophenyl octylether, and 32.0% (w/w) polyvinyl chloride. The developed sensor displayed a linear response in the copper (II) concentration ranging from 1.0 × 10–6 to 1.0 × 10–1 M with a correlation coefficient of 0.9993 and a slope of 29.8 ± 0.6 mV/decade of activity. The response time, detection limit, and pH working range were determined to be 4 s, 3.8 × 10–7 M and 4.0–8.0, respectively. The developed sensor showed highly selective and satisfactory potentiometric response for the determination of copper (II) in a Turkish coin.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2019Synthesis and characterization of ZnO nanorice decorated TiO2 nanotubes for enhanced photocatalytic activity
Bozkurt Çırak, Burcu; Caglar, Bulent; Kılınç, Tuba; Morkoç Karadeniz, Sibel; Erdoğan, Yaşar; Kılıç, Selçuk; Kahveci, Enver; Ercan Ekinci, Ali; Çırak, Çağrı
In present study, we report on the synthesis of TiO2/ZnO nanocomposite (TZN) films for potential applications as photocatalyst in heterogeneous photo-degradation of Rhodamine B under UVA irradiations. ZnO nano-rice decorated TiO2 nanotubes were successfully synthesized via a facile and effective two-step route. Firstly, TiO2 nanotube arrays were grown by anodic oxidation. Afterwards, ZnO rice shaped nanostructures were decorated by successive chemical bath deposition cycles of 2, 4, 6 and 8. The XRD, FESEM, XPS and μ-XRF results showed that the rice-shaped wurtzite ZnO nanoparticles with dimensions of ca. 1μm × 100 nm were homogeneously distributed on the anatase TiO2 nanotube arrays with highly uniform in the presence of in zinc nitrate hexahydrate and hexamethylenetetramine precursors with 1:4 M ratios. The photodegradation results showed that the photocatalytic activity of TZN films were gradually increased in parallel with the number of ZnO deposition cycles and the best performance was found for TNZ8 film. The RhB photodegradation efficiency was determined to be 65% for bare TiO2 whereas 95% degradation of Rhodamine B was occurred for TNZ8 film which follow pseudo-first-order kinetic. In addition, TZN films exhibited good photostability after four reuses. Also, photocatalytic activity of TZN were tested under UVC, UVB, UVA and visible region irradiations for comparative purposes.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2019Novel silver(I) complexes bearing mefenamic acid and pyridine derivatives: Synthesis, chemical characterization and in vitro anticancer evaluation
Altay, Ahmet; Caglar, Sema; Caglar, Bulent; Sahin, Zarife Sibel
Two Ag(I) complexes [Ag2(μ-mef)2(2-pymet)2] 1, [Ag2(μ-mef)2(2-pyet)2] 2 containing mefenamic acid, 2-pyridinemethanol and 2-pyridineethanol were synthesized and characterized by using SCXRD, FT-IR, elemental and thermal analysis techniques. The complex 1 was synthesized as a single crystal whereas the complex 2 was obtained as a microcrystalline powder. The complex 1 consists of binuclear structure. The argentophilic interaction occurs among silver(I) ions due to the short Ag⋯Ag distance (2.8710(10) Å). Two Ag(I) centers are connected by carboxylato oxygen-bridge to form the binuclear metal core. The FT-IR spectra and thermal analysis studies confirmed that both complexes exhibited similar structures. In vitro antiproliferative activity of both complexes were evaluated against MCF-7, HT-29 and HepG2 cancer cell lines. The apoptotic effects and intracellular ROS generation from both complexes were investigated in MCF-7 cell line by flow cytometry analysis. The XTT and LDH assays revealed that both complexes showed strong antiproliferative activity with higher selectivity towards cancer cells compared to the normal cells. In addition, Annexin V/propidium iodide assay exhibited that apoptotic cell number was increased in MCF-7 cells with increasing concentrations of Ag(I) complexes. Furthermore, both complexes induced the ROS generation considerably in MCF-7 cells suggesting the possible pro-oxidant activity of the novel synthesized Ag(I) complexes. Taken together, these findings provide a notable support for potential utility of Ag(I) complexes as novel anticancer agents against numerous kind of carcinogenesis.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2019Voltammetric detection of chlorite ion using carbon paste sensor modified with N-cetylpyridinium–bentonite
Cubuk, Osman; Colak, Isıl; Özdokur, Kemal Volkan; Caglar, Bulent; Coldur, Fatih; Topcu, Cihan
A voltammetric carbon paste sensor (CPS) was described for the detection of chlorite ion in water analysis. For the construction of the voltammetric CPS, organo-bentonites were synthesised by intercalation of N-cetylpyridinium (NCP) at different amounts into interlayer gap of bentonite. Some features of the obtained organo-bentonites such as structural, thermal and morphological were investigated by using various techniques. Afterwards, the voltammetric behaviour of the (Formula presented.) solution was investigated with cyclic voltammetry in the potential range of 0.0–1.0 V at a scan rate of 50 mV s−1 based on the obtained organo-bentonites as electroactive material. The characterisation of the prepared organo-bentonites as electroactive material, the effect of the amount of NCP–bentonite (NCP–B) in modified CPS on the 10.0 mM CIO2- response was tested by chancing the percentage of NCP–B in the range of 2.50–12.50% under identical experimental conditions. The pH of the measurement cell was optimised by using 0.04 M Britton–Robinson buffer in the range of pH 2.0–12.0. Under the optimised conditions, developed sensor exhibited a linear response in the range of 2.0 × 10−5 to 2.0 × 10−4 M chlorite ions concentrations. The detection limit and the limit of quantification were figured out as 6.0 × 10−6 and 2.0 × 10−5 M, respectively. The repeatability and reproducibility of the sensor were calculated as 5.0% and 6.8% (N = 5), respectively. Finally, the sensor was successfully applied for the analysis of bottled water, and the mean recovery was found as 103 ± 3%.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2019Synthesis of TiO 2 nanotube/ZnO nanorod hybrid nanocomposite photoanodes for dye-sensitized solar cells
Çırak, Burcu Bozkurt; Demir, Zeynep; Eden, Çiğdem; Erdoğan, Yaşar; Caglar, Bulent; Karadeniz, Sibel Morkoç; Kılınç, Tuba; Ekinci, Ali Ercan; Çırak, Çağrı
TiO 2 nanotube/ZnO nanorod hybrid nanocomposite (ZTN) photoanodes were synthesized, characterized and assembled as dye-sensitized solar cells (DSSCs) at optimum conditions for improving photovoltaic efficiency. The self-organized and high ordered TiO 2 nanotube arrays were growth on titanium foil by anodic oxidation as a substrate for ZnO decoration by hydrothermal method. Zinc nitrate hexahydrate and hexamethylenetetramine precursor concentrations were varied to designate the optimum ZnO decoration density for enhanced photoconversion efficiency. XRD, FESEM and XPS results showed that the crystal structure, morphology, elemental composition and density of ZnO nanorods on the surface of TiO 2 nanotubes are very sensitive to ZnO precursor concentrations. It is found that, the highest overall efficiency of DSSC based on ZTN photoanode was measured 1.8% for precursor concentration of 60 mM which was more than double compared to DSSC based on bare-TiO 2 nanotubes (0.8%). The improvement of DSSC efficiency originates from suppressing the recombination rate and decreasing the charge transfer resistance due to synergetic effect between TiO 2 nanotubes and ZnO nanorods.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2018Fe3O4 nanoparticles decorated smectite nanocomposite: Characterization, photocatalytic and electrocatalytic activities
Caglar, Bulent; Guner, Eda Keles; Keles, Kubra; Özdokur, Kemal Volkan; Cubuk, Osman; Coldur, Fatih; Caglar, Sema; Topcu, Cihan; Tabak, Ahmet
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 photodegradation 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 μM, respectively.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2018Structural characterization of chitosan-smectite nanocomposite and its application in the development of a novel potentiometric monohydrogen phosphate-selective sensor
Topcu, Cihan; Caglar, Bulent; Onder, Ahmet; Coldur, Fatih; Caglar, Sema; Guner, Eda Keles; Cubuk, Osman; Tabak, Ahmet
Chitosan-smectite biocomposite was prepared by intercalation of protonated chitosan molecules into the interlayer space of smectite in monolayer arrangement through cation exchange mechanism and the obtained biocomposite was successfully used as an electroactive component in the structure of a PVC membrane potentiometric sensor for the direct and highly selective determination of monohydrogen phosphate ions. The comparative elemental, structural, thermal and morphological analysis of starting-smectite, neat chitosan and chitosan-smectite were investigated by utilizing EDX, XRD, ATR-FTIR, TG/DTG/DTA, SEM and surface area measurement techniques. The optimum membrane composition, detection limit, response time, pH working range and repeatability of the proposed electrode were determined.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2018Fabrication of TiO2/ZnO/Pt nanocomposite electrode with enhanced electrocatalytic activity for methanol oxidation
Özdokur, Kemal Volkan; Çırak, Burcu Bozkurt; Caglar, Bulent; Çırak, Çağrı; Karadeniz, Sibel Morkoç; Kılınç, Tuba; Erdoğan, Yaşar; Ekinci, Ali Ercan
Platinum decorated heterogeneous catalysts for methanol oxidation reaction have crucial importance for the commercial sustainability of Direct Methanol Fuel Cells (DMFC). In this study, TiO2/ZnO/Pt nanocomposite film was fabricated as a promising electrocatalytic surface to enhance methanol oxidation in alkaline medium. Firstly, an TiO2/ZnO layer was prepared via DC sputtering followed by electrodeposition techniques on FTO electrode and then platinum nanoparticles were decorated onto the obtained nanocomposite film for the first time. The characterization of the developed transparent films was performed by using field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), cycling voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The XRD, FESEM and XPS results showed that metallic Pt nanoparticles were uniformly distributed onto the TiO2/ZnO film consisting of anatase TiO2 and wurtzite ZnO layers with a thickness of ca. 370 and 320 nm, respectively. Five cycles of deposition of ZnO and Pt nanoparticles showed best catalytic activity after optimization. The oxidation peak of 0.5 M methanol at TiO2/ZnO/Pt was located at −0.17 V and the corresponding peak current increased about 10- and 5-fold in comparison to FTO/Pt and FTO/TiO2/Pt electrodes, respectively.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2018Synthesis, structural, thermal elucidation and in vitro anticancer activity of novel silver(I) complexes with non-steroidal anti-inflammatory drugs diclofenac and mefenamic acid including picoline derivatives
Altay, Ahmet; Caglar, Sema; Caglar, Bulent; Sahin, Onur
Six new Ag(I) coordination complexes, namely [Ag4(μ-dicl)4(2-pic)3] 1, [Ag2(μ-mef)2(2-pic)2] 2, [Ag2(μ-dicl)2(3-pic)2] 3, [Ag2(μ-mef)2(3-pic)2] 4, [Ag2(μ-dicl)2(4-pic)2] 5 and [Ag2(μ-mef)2(4-pic)2] 6, were synthesized and characterized by elemental analysis, FT-IR and thermal analysis techniques. The crystal structures of 1, 3, 4 and 5 were determined by X-ray diffraction analysis, whereas 2 and 6 were obtained as microcrystalline powders. X-ray diffraction analysis demonstrated that 1 occurs as a tetranuclear complex, while 3, 4 and 5 have binuclear structures. A short Ag⋯Ag distances of 2.8446 and 2.8823 Å for 1, 2.8409 Å for 3, 2.8942 Å for 4 and 2.8423 Å for 5 were found in the complexes, indicating that argentophilic interactions exist between the silver ions. In 1, the dicl ligands act as μ3-O,O′,O′ bridging ligands between three Ag(I) ions. In 3, 4 and 5, the dicl and mef ligands behave as bridging ligands and bind two Ag(I) ions together with the carboxylato oxygen atoms. The simultaneous TG/DTG and DTA techniques were applied to interpret the mass losses, decomposition temperatures and corresponding processes of the thermal behaviours of the complexes. The experimental and calculated mass losses of the proposed structures for complexes 2 and 6 are quite compatible with each other and these complexes have very similar FT-IR spectra to the other complexes, which reflect their same structural geometries and characteristics. The cytotoxic activities of the complexes (1–6) were tested against three different cancer cell lines, MCF-7, HT-29 and HepG2, and one normal cell line, 3 T3-L1. XTT assay results demonstrated that although all the silver(I) complexes showed good cytotoxic activity, depending on the cell types tested, the complexes with mefanamic acid (2, 4 and 6) were found to predominate over those with diclofenac (1, 3 and 5), as well as the superiority of 3-picoline to 4-picoline and 2-picoline. Moreover, compared with the cytotoxic potential of carboplatin, 4 especially exhibited a significant cancer cell inhibitory rate and lower cytotoxicity toward the normal cell line, with much higher selectivity indexes.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2018Electrochemical Determination of Copper(II) in Water Samples Using a Novel Ion-Selective Electrode Based on a Graphite Oxide–Imprinted Polymer Composite
Topcu, Cihan; Lacin, Gamze; Yilmaz, Vedat; Coldur, Fatih; Caglar, Bulent; Cubuk, Osman; Isildak, Ibrahim
A novel copper(II)-selective electrode based on graphite oxide/imprinted polymer composite was developed for the electrochemical monitoring of copper(II) (Cu2+) ions. The electrode exhibited highly selective potentiometric response to Cu2+ with respect to common alkaline, alkaline earth and heavy metal cations. The composite composition studies indicated that the most suitable composite composition performing the most promising potentiometric properties was 20.0% ionophore (Cu2+-ion imprinted polymer), 10.0% paraffin oil, 5.0% multiwalled carbon nanotubes, and 65.0% graphite oxide. The fabricated electrode exhibited a linear response to Cu2+ over the concentration range of 1.0 × 10− 6–1.0 × 10− 1 M (correlation coefficient of 0.9998) with a sensitivity of 26.1 ± 0.9 mV decade− 1. The detection limit of the fabricated electrode was determined to be 4.0 × 10− 7 M. The electrode worked well in the pH range of 4.0–8.0. The electrode had stable, reversible and fast potentiometric response (3 s). In addition, the electrode had a lifetime of more than 1 year. The analytical applications of the proposed electrode were performed using as an indicator electrode for the potentiometric titration of Cu2+ with ethylene diamine tetraacetic acid solution and for the determination of Cu2+ of spiked river, dam, and tap water samples. The obtained results for potentiometric titration and water samples were satisfactory.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2017Synthesis, crystal structure, spectroscopy, thermal properties and carbonic anhydrase activities of new metal(II) complexes with mefenamic acid and picoline derivatives
Dilek, Esra; Caglar, Sema; Dogancay, Nesrin; Caglar, Bulent; Sahin, Onur; Tabak, Ahmet
The mononuclear six metal(II) complexes ([Co(mef)2(3-pic)2(CH3OH)2] (1), [Ni(mef)2(3-pic)2(CH3OH)2] (2), [Cu(mef)2(3-pic)2] (3), [Co(mef)2(4-pic)2] (4), [Ni(mef)2(4-pic)2] (5), and [Cu(mef)2(4-pic)2] (6) with mefenamic acid and picoline ligands were synthesized, characterized, and their carbonic anhydrase inhibitory activities were evaluated. The six complexes were characterized by elemental analysis, FT-IR spectroscopy, and thermal analyses. The crystal structures of 1, 3, and 6 were determined by X-ray crystallography. The complexes have octahedral geometry. In 1, the mefenamato ligand behaved as monodentate whereas in 3 and 6, the mefenamato ligand acted as a bidentate ligand. Complexes 3 and 6 consist of the mefenamate and 4-picoline ligands. In 1, unlike the other complexes, methanol acted as a ligand and was involved in the coordination. Carbonic anhydrase I and II isoenzymes were purified from human erythrocytes. The in vitro effects of mefenamic acid, 3-picoline, 4-picoline, and the six metal(II) complexes on these isoenzymes were evaluated.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2017Synthesis, surface properties, crystal structure and dye sensitized solar cell performance of TiO2 nanotube arrays anodized under different voltages
Bozkurt Çırak, Burcu; Karadeniz, Sibel Morkoç; Kılınç, Tuba; Caglar, Bulent; Ekinci, Ali Ercan; Yelgin, Hüseyin; Kürekçi, Mehmet; Çırak, Çağrı
In this study, anodic TiO2 nanotube (TNT) arrays with average nanotube diameter from 26 nm to 115 nm and length from 1.3 μm to 6.4 μm were grown by electrochemical method. Anodization process were performed under different voltages from 10 to 50 V in ethylene glycol – ammonium fluoride – water electrolyte. Formation mechanism of TNTs was summarized. Surface morphology, crystal structure, roughness, wettability and elasticity of TNT arrays were characterized by using field emission scanning electron microscope (FESEM), X-Ray diffraction (XRD), atomic force microscope (AFM), optical tensiometer and universal mechanical tester, respectively. Water contact angle measurements and nanoindentation tests proved that water contact angle and elastic modulus of TNT arrays decrease with increasing anodization voltage. Photocurrent-photovoltage curves and electrochemical impedance spectroscopy (EIS) measurements of dye sensitized solar cells (DSSC) were made to investigate the effects of anodization voltages on photoanode performance. The light conversion efficiency and photocurrent density of TNT photoanodes was increased with increasing anodization voltage due to larger nanotube length and surface area. The results show that anodization voltage is significant parameter for the surface properties and dye sensitized solar cell (DSSC) performance TNT arrays.
RDL Kalıcı Kaydıİncele - ArticleAçık Erişim2017Structural, thermal and morphological properties of a novel poly(acrylamide-comethacrylic acid)/organoclay nanocomposite
Caglar, Bulent; Coldur, Fatih; Caglar, Sema; Cubuk, Osman; Tabak, Ahmet; Topcu, Cihan
A novel poly(acrylamide-co-methacrylic acid)/organoclay nanocomposite was prepared and its structural, thermal, and morphological properties were investigated by various techniques. The absence of diffraction peaks for the organomodified-smectite nanocomposite showed that dispersion of the clay nanolayers within the polymer matrix was in the form of an exfoliated nanostructure. Morphological studies confirmed that organomodified-clay dispersed homogeneously in the polymer matrix. Infrared spectroscopy results indicated that the organosmectite is physically dispersed in the polymer network without forming any chemical bonds. The thermal analysis data revealed that there are significant increases in temperatures of decomposition and softening points of polymer with addition of organoclay.
RDL Kalıcı Kaydıİncele - ArticleYalnız künye2016Structural, thermal, morphological and surface charge properties of dodecyltrimethylammonium-smectite composites
Caglar, Bulent; Topcu, Cihan; Coldur, Fatih; Sarp, Gokhan; Caglar, Sema; Tabak, Ahmet; Sahin, Erdal
The present investigation was undertaken to obtain information about the structural, thermal, morphological, surface charge and textural properties of the synthesized dodecyltrimethylammonium-smectite composites at various surfactant concentrations by means of powder X-ray diffraction, attenuated total reflection Fourier transform infrared, thermal analyses, scanning electron microscopy, electrophoretic mobility and surface area measurement techniques. The basal spacing values of organo-smectites varied between 13.55 and 17.00 Å that point out the successful intercalation of the surfactant cations into smectite layers with different molecular arrangements either lateral monolayer or lateral bilayer. Intercalation of surfactant cations led to appreciable decreases in the intensities of the bands at 3402 and 1635 cm-1 which originate from OH stretching and bending vibration of sorbed water molecules, respectively. Thermal analysis data showed that all organo-smectites had lower adsorbed water losses than raw and sodium-smectite and the removal of surfactant species occurred in the temperature range of 130-720 °C. The specific surface areas, pore volumes and micropore surface areas of organo-smectites decreased while the average pore width of these species increased with respect to that of raw smectite. The surfactant cations located in the interlayer spaces caused significant alterations in electrophoretic mobility values and morphology of raw smectite.
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