Zafer Üstündağ

A novel magnetic Fe@Au core–shell nanoparticles anchored graphene oxide recyclable nanocatalyst for the reduction of nitrophenol compounds

In this study, a novel catalyst based on Fe@Au bimetallic nanoparticles involved graphene oxide was prepared and characterized by transmission electron microscope (TEM), and x-ray photoelectron spectroscopy (XPS). The nanomaterial was used in catalytic reductions of 4-nitrophenol and 2-nitrophenol in the presence of sodium borohydride. The experimental parameters such as temperature, the dosage of catalyst and the concentration of sodium borohydride were studied. The rates of catalytic reduction of the nitrophenol compounds have been found as the sequence: 4-nitrophenol>2-nitrophenol. The kinetic and thermodynamic parameters of nitrophenol compounds were determined. Activation energies were found as 2.33 kcal mol(-1) and 3.16 kcal mol(-1) for 4-nitrophenol and 2-nitrophenol, respectively. The nanomaterial was separated from the product by using a magnet and recycled after the reduction of nitrophenol compounds. The recyclable of the nanocatalyst is economically significant in industry.

A novel glucose biosensor platform based on Ag@AuNPs modified graphene oxide nanocomposite and SERS application

This study represents a novel template demonstration of a glucose biosensor based on mercaptophenyl boronic acid (MBA) terminated Ag@AuNPs/graphene oxide (Ag@AuNPs-GO) nanomaterials. The nanocomposites were characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) method. The TEM image shows that Ag@AuNPs in the nanocomposite is in the range of diameters of 10-20 nm. The nanocomposite was used for the determination of glucose through the complexation between boronic acid and diol groups of glucose. Thus, a novel glucose biosensor was further fabricated by immobilizing glucose oxidase (GOD) into MBA terminated Ag@AuNPs-GO nanocomposite film (MBA-Ag@AuNPs-GO). The linearity range of glucose was obtained as 2-6mM with detection limit of 0.33 mM. The developed biosensor was also applied successfully for the determination of glucose in blood samples. The concentration value of glucose in blood samples was calculated to be 1.97±0.002 mM from measurements repeated for six times.

Effect of Au and Au@Ag core–shell nanoparticles on the SERS of bridging organic molecules

Gold nanoparticles (AuNPs) with about 6 nm size were produced and stabilized with mercaptopropionic acid (MPA) film to produce a monolayer protected cluster (MPC) of AuS(CH(2))(2)COOH. 4-Aminothiophenol (ATP) molecules were introduced to the activated carboxylic acid ends of the film surrounding the AuNPs to produce AuS(CH(2))(2)CONHPhSH MPC. These modified AuNPs were again self-assembled with Au@Ag core-shell bimetallic nanoparticles via the -SH groups to produce an organic bridge between Au and Au@Ag metallic nanoparticles. An unusually strong enhancement of the Raman signals was observed and assigned to the plasmon coupling between the AuNPs and Au@Ag NPs bridged assembly. Formation of AuS(CH(2))(2)COOH and AuS(CH(2))(2)CONHPhSH clusters and AuS(CH(2))(2)CONHPhS(Au@Ag) assembly is confirmed by UV-Vis, reflection-absorption IR spectroscopy (RAIRS) and X-ray photoelectron spectroscopy (XPS), as well as by TEM analysis. The SERS activity of the AuNPs and Au@Ag NPs was tested using the HS(CH(2))(2)CONHPhSH molecule as a probe to compare the effectiveness of monometallic and bimetallic systems. SERS spectra show that Au@Ag bimetallic nanoparticles are very effective SERS-active substrates.

High catalytic activity of electrochemically reduced graphene composite toward electrochemical sensing of Orange II

Orange II, an azo dye, is sometimes illegally used as a red dye in food products despite its adverse health effects if consumed. Therefore, the determination of low concentrations of Orange II is an important target. An Orange II sensor was prepared using electrochemically reduced graphene oxide grafted with 5-amino-1,3,4-thiadiazole-2-thiol-Pt nanoparticles (denoted as ERGO-ATDT-Pt) onto a glassy carbon electrode (GCE) and investigated for Orange II detection in 0.1M acetate buffer solution (ABS at pH 4.5) with prominent reversible redox peaks. A wide linear range of 1×10(-)(8)-6×10(-)(7)M with a low detection limit of 3.4×10(-)(10)M (s/n=3) was found for Orange II detection. This developed ERGO-ATDT-Pt/GCE sensor showed good selectivity, excellent stability and better response to the real sample analysis with excellent recovery.

Phosphorus-Nitrogen Compounds: Part 25. Syntheses, Spectroscopic, Structural and Electrochemical Investigations, Antimicrobial Activities, and DNA Interactions of Ferrocenyldiaminocyclotriphosphazenes

Abstract The condensation reactions of hexachlorocyclotriphosphazene (N3P3Cl6) with mono (1 and 2) and bisferrocenyldiamines (3–5 and 7) resulted in the formation of tetrachloro mono- (8 and 9) and bisferrocenylspirocyclotriphosphazenes (10–13). In addition the tetramorpholino mono- (8a and 9a) and bisferrocenylphosphazenes (10a–12a) were obtained from the reactions of the corresponding tetrachlorophosphazenes (8–12) with excess morpholine. The structures of all the phosphazenes were determined using FTIR, MS, 1H, 13C, and 31P NMR and 2-dimensional NMR techniques. The structures of 9a and 13 were determined by single crystal X-ray diffraction techniques. Cyclic voltammetric investigations of compounds 8a, 9a, and 11a revealed that ferrocene redox centers undergo reversible oxidation. These ferrocenylphosphazenes appear to be quite robust electrochemically. Interactions between the compounds 8a, 9a, 11a, and 12a and pBR322 plasmid DNA were investigated by agarose gel electrophoresis. [Supplementary materials are available for this article. Go to the publishers online edition of Phosphorus, Sulfer, and Silicon and the Related Elements for the following free supplemental files: Additional text and figures.] GRAPHICAL ABSTRACT

Phosphorus-nitrogen compounds Part 17: The synthesis, spectral and electrochemical investigations of porphyrino-phosphazenes

The reactions of unsymmetrical porphyrins (1 and 2) with Ni(OAc)2·4H2O in boiling DMF produce porphyrin complexes (3 and 4). From the reactions of free porphyrin ligands 1 and 2 with hexachlorocyclotriphosphazatriene, N3P3Cl6, the new free porphyrino-phosphazene derivatives (5 and 6) are obtained. On the other hand, the reactions of N3P3Cl6 with porphyrin complexes (3 and 4) afford the new porphyrino-phosphazene complexes (7 and 8). In the literature there are a few examples of the porphyrino-phosphazene architectures. The structural investigations of all the compounds have been made by elemental analyses, MS, FTIR, 1H NMR, 31P NMR and UV-visible techniques. The cyclic voltammograms (CVs) are examined in acetonitrile (MeCN) containing 0.1 M tetrabutylammonium-tetrafluoroborate (TBATFB) to investigate the surface attachment properties at the glassy carbon electrode (GCE) and the influence of the presence of metal cations in the porphyrin ring.

Analysis of 2-Benzo[c]cinnoline Nanofilm at the Gold Surface

Abstract A polycrystalline gold surface was modified with 2-benzo[c]cinnoline (BCC) in nonaqueous media using cyclic voltammetry. A multilayer BCC nanofilm at the gold surface was formed by the electrochemical reduction of 2-benzo[c]cinnoline diazonium salt (BCC-DAS). Grafting of BCC molecules onto the gold surface was verified by cyclic voltammetry using various redox probes, electrochemical impedance spectroscopy, and Raman spectroscopy. The BCC film thickness was measured by ellipsometry and calculated as 46 nm indicating a multilayer film formation. The stability and the potential range of the novel Au-BCC modified electrode were also studied in open atmosphere and pure water. The working potential range of Au-BCC electrode was found to be between −1.8 and +1.6 V.

A novel Surface Plasmon Resonance enhanced Total Internal Reflection Ellipsometric application: electrochemically grafted isophthalic acid nanofilm on gold surface.

The scope of this study is to modify a Surface Plasmon Resonance (SPR) sensor slide with isophthalic acid to evaluate the possible application on the detection of copper(II) ions in aqueous media by total internal reflection ellipsometry. A gold sensor surface was modified by an electrochemical diazonium reduction modification method. The modified surfaces are characterized with cyclic voltammetry (CV) and ellipsometry. Isophthalic acid monolayer modified gold slides were used for in situ detection of aqueous Cu(2+) solution with the SPR enhanced total internal reflection ellipsometry (SPRe-TIRE) technique. Layer formation, pH dependency of adsorption, sensor response of the SPRe-TIRE and isothermal kinetic parameters were examined. A high dependency on the number of CV cycles in the monolayer-multiple layer transition was observed. The suggested sensor gave a linear response over a wide range of Cu(2+) concentrations. It was also reported that adsorption on the SPRe-TIRE sensor gave Langmuir adsorption model behavior.

Syntheses and modifications of bisdiazonium salts of 3,8-benzo[c]cinnoline and 3,8-benzo[c]cinnoline 5-oxide onto glassy carbon electrode and the characterization of the modified surfaces

The goal of this study was to prepare novel glassy carbon electrode surfaces using two similar bis-diazonium salts, 3,8-benzo[c]cinnoline (3,8-BCC-BDAS) and 3,8-benzo[c]cinnoline 5-oxide (3,8-BCCNO-BDAS) at the glassy carbon (GC) surface. These diazonium salts were reduced electrochemically and covalently electrografted onto the glassy carbon electrode surface to form modified electrodes. Electrochemical reduction of 3,8-BCC-BDAS and 3,8-BCCNO-BDAS salts on the electrode surface yielded a compact and stable film. The existence of BCC moieties on the GC surface was characterized by X-ray photoelectron spectroscopy, reflectance-adsorption infrared spectroscopy, cyclic voltammetry, ellipsometry, and electrochemical impedance spectroscopy. The stability and working potential range of the novel modified electrodes were also studied. The possibility of analytical application of these novel surfaces for inorganic cations and especially selectivity to copper ions was investigated. 3,8-diaminobenzo[c]cinnoline (3,8-DABCC) and its 5-oxide derivative (3,8-DABCCNO) were synthesized from the reductive cyclization of 2,2′-dinitrobenzidine and prepared their bisdiazonium salts via the tetrazotization reactions of the diamines with NaNO2. The structures of 3,8-DABCC and 3,8-DABCCNO and their corresponding bisdiazonium salts are confirmed by spectral analysis.

Sources of Environmental Pollution in Ankara (Turkey): Geochemistry and Traffic Effects—PEDXRF Applications

ABSTRACT Road dusts were collected from the main streets in the vicinity of Ankara, the capital city of Turkey, including exhaust dust samples from the different fuel-based motor vehicles and sample pieces of brake pads to characterize their metal compositions by polarized energy-dispersive X-ray fluorescence (PEDXRF) spectrometry. Road dust samples were gathered by a vacuum dust sweeper from nine different densely populated residential settlement regions of Ankara, far from large industrial plants. Heavy metal contents of the road dusts were analyzed during the summertime to determine the metal pollution due to the motor vehicle exhaust, abrasion of brake pads, and lithology, ignoring the industrial and heating sources of pollution. The results of the analysis showed that the elements of Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Sn, Pb, and Th in road dust samples were not derived from the lithology and industrial plants but from the motor fuel exhausts and brake pad abrasion. Generally, urban environmental pollution due to the toxic trace metals from traffic is harmful for the human health as well as the ecosystems near Ankara.