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Öğe Effect of Au and Au@ag Core-Shell Nanoparticles on the SERS of Bridging Organic Molecules(ACADEMIC PRESS INC ELSEVIER SCIENCE, 2010) Güzel, Remziye; Üstündağ, Zafer; Ekşi, Haslet; Keskin, Selda; Taner, Bilge; Durgun, Zeynep Gülşah; Turan, Aybüke A. İşbir; Solak, Ali OsmanGold 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(CH2)(2)COOH. 4-Aminothiophenol (ATP) molecules were introduced to the activated carboxylic acid ends of the film surrounding the AuNPs to produce AuS(CH2)(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(CH2)(2)COOH and AuS(CH2)(2)CONHPhSH clusters and AuS(CH2)(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(CH2)(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.Öğe Fabrication of Calix[4]pyrrole Nanofilms at the Glassy Carbon Surface and Their Characterization by Spectroscopic, Optic and Electrochemical Methods(Elsevier Science Sa, 2010) Taner, Bilge; Özcan, Emine; Üstündağ, Zafer; Keskin, Selda; Solak, Ali Osman; Ekşi, Hasletmeso-Octamethylcalix[4]pyrrole (CP) and meso-heptaethylcalix[4]pyrrole-meso-4-aminophenyl (4APCP) modified glassy carbon (GC) electrodes were prepared by the electrochemical oxidation in acetonitrile solution. Binding of the calix[4]pyrroles with the glassy carbon surface was investigated that it is through the etheric linkage revealed from the reflection absorption infrared spectroscopy (RAIRS). Surface films of CP and 4APCP were investigated by cyclic voltammetry (CV), ellipsometry, X-ray photoelectron spectroscopy. RAIRS and the contact angle measurements. The thicknesses of the films were determined by ellipsometry which confirmed that the film was multilayer and homogeneous over the surface. Ellipsometric measurements also provided that the CP and 4APCP film thicknesses were 2.49 nm and 4.58 nm for 6 CV cycle modification, corresponding to 66 mu F/cm(2) and 106 mu F/cm(2) capacitances obtained by CV. The wetting behavior was examined by contact angle measurements and found that the hydrophobicity of the GC-4APCP surface was higher than that of GC-CP, probably due to the aromatic meso substituent present in the former.Öğe Modification of glassy carbon electrode by the electrochemical oxidation of 3-aminophenylcalix[4]pyrrole in nonaqueous media(Wiley, 2012) Taner, Bilge; Deveci, Pervin; Üstündağ, Zafer; Keskin, Selda; Özcan, Emine; Solak, Ali Osman3-Aminophenylcalix[4]pyrrole (3APCP) was grafted to a glassy carbon (GC) surface during the electrochemical oxidation process in 0.1 M tetrabutylammoniumtetra-fluoroborate (TBATFB) containing acetonitrile solution. The presence of a surface film was confirmed electrochemically by comparing voltammograms of dopamine and ferricyanide redox probes at the bare and modified electrodes. Reflection-absorption infrared spectroscopy (RAIRS), XPS, atomic force microscopy (AFM), ellipsometry and the contact angle measurements were also employed to characterize 3APCP film on GC electrode. RAIRS analysis revealed that calix[4]pyrrole was bonded to the glassy carbon surface via the etheric linkage. The stability of the modified GC electrode was also studied. Copyright (C) 2011 John Wiley & Sons, Ltd.Öğe Synthesis, Enhanced Spectroscopic Characterization and Electrochemical Grafting of N-(4-Aminophenyl)aza-18-Crown-6: Application of Dept, Hetcor, Hmbc-Nmr and X-Ray Photoelectron Spectroscopy(ELSEVIER, 2010) Deveci, Pervin; Taner, Bilge; Üstündağ, Zafer; Özcan, Emine; Solak, Ali Osman; Kılıç, ZeynelThis work describes the synthesis, characterization and electrochemical grafting of N-(4-Aminophenyl)aza-18-Crown-6 (4APA18C6). The key step in the synthesis is the reaction of N-phenylaza-18-crown-6 (PA18C6) with sodium nitrite. The compound, N-(4-nitrosophenyl)aza-18-crown-6 (NOPA18C6) could not be isolated purely from the reaction mixture, but a reduction of the residue with SnCl2 gave the desired aza-crown ether, N-(4-aminophenyl)aza-18-crown-6 (4APA18C6). To confirm its proposed structure detailed characterization techniques such as elemental analysis, FT-IR, H-1 NMR, C-13 NMR, DEPT, HETCOR, HMBC and ESI mass-spectrometry were used. Due to the importance of azacrown compounds in the field of analytical chemistry, in the derivatization of dyes, chemical sensors and ionic extraction, as molecular receptors, grafting of 4APA18C6 on the glassy carbon (GC) surface has been investigated by amine oxidation to gain new insight into the modification area. The oxidation mechanism has been established, and the results are in accordance with the attachment of amines to a glassy carbon surface by cyclic voltammetry. The modification of 4APA18C6 molecules onto the glassy carbon surface was verified by cyclic voltammetry (CV), X-ray photoelectron spectroscopy (XPS) reflection-absorption infrared spectroscopy (RAIRS) and ellipsometry. The film on the GC surface was formed according to the layer-by-layer mechanism and the ellipsometric thickness was obtained around 11.5 +/- 1.1 nm.
