Orhan Güney

Reversible adsorption of calcium ions by imprinted temperature sensitive gels

With the aim of developing polymeric gels sensitive to external stimuli and able to reversibly adsorb and release divalent ions, copolymer gels of N-isopropylacrylamide (NIPA) and methacrylic (MAA) monomers were prepared. We chose calcium as a target divalent ion. Two MAAs form a complex with a calcium ion, and the NIPA component allows the polymers to swell and shrink reversibly in response to temperature. The adsorbing site develops an affinity to target ions when the adsorbing molecules come into proximity, but when they are separated, the affinity diminishes. To enhance the affinity to calcium, an imprinting technique was applied using Ca2+ and Pb2+ ions as templates in methylsulfoxide and dioxane media, respectively. The adsorption capacity of the imprinted gels was compared with that of the nonimprinted gels, and the effects of the templates, the solvents, and the amount of methacrylic monomers used in the synthesis and the medium temperature over the Ca2+ adsorption capacity of the gels from aqueou...

Elucidation of multiple-point interactions of pyranine fluoroprobe during the gelation

We have studied the multiple-point interactions of the pyranine (8-hydroxypyrene-1,3,6-trisulfonic acid, trisodium salt; 3sPyOH) fluoroprobe with polymer chains during the free-radical polymerization of acrylamide (AAm) by using the steady state fluorescence measurements. We observed a considerable blue shift from 515nm to 406nm in the emission spectra due to a C-O ether bond formation between the hydroxylic oxygen of 3sPyOH and a terminal C-atom of the growing AAm chain. Furthermore ionic (electrostatic) interactions occur between the three ionized sulfonic acid groups (SO(3)(-)) of 3sPyOH and protonated amide groups on the AAm chains. These electrostatic interactions also cause a gradual red shift in the maximum of the short-wavelength-peak, from 406nm to 430nm. The results showed that the pyranine can be used as a probe for real time monitoring of the polymerization process of AAm system since it monitors both the progression of the polymerization via chemical binding over OH group and the change in the local density of the polymerizing sample by means of the gradual red shift in the short-wavelength-peak via ionic interactions over SO(3)(-) groups.

The polymerization of acrylamide initiated with CE(IV) and KMNO4 redox systems in the presence of glycine

Glycine-Ce(IV) salts and -KMnO 4 initiator systems were used for the polymerization of acrylamide, resulting in water-soluble polyacrylamide, which contains amino acid end groups. The dependence of polymerization yields and molecular weights of polymers on the mole ratio of acrylamide monomer to glycine, the polymerization time, the temperature, and the concentration of sulfuric acid were investigated. The decrease in the mole ratio of acrylamide to glycine resulted in a decrease in the molecular weight, and an increase in the yield of acrylamide polymer, which contains a glycine end group. With increasing acid concentration of the polymeric solution, the polymerization yield and the molecular weight of polymer decrease. Ce(IV) and Mn(IV) reduced to Ce(III) and Mn(II) in the polymerization reaction. The amounts of Ce(III) and Mn(II) bound to polymer were determined. The composition of the polymerization product was investigated and a bimodal character of the molecular weight distribution was observed. The mechanism of this phenomena is discussed.

Effects of coumarin substituents on the photophysical properties of newly synthesised phthalocyanine derivatives

In this study, synthesis of new ligands, 8-hydroxy-3-[p-(3′,4′-dicyanophenoxy)-phenyl]coumarin and 8-hexyloxy-3-[p-(3′,4′-dicyanophenoxy)-phenyl]coumarin, and their phthalocyanines, 2,9,16,23-tetrakis[8-hexyloxy-3-(4-oxyphenyl)coumarin]-metal-free and metallophthalocyanines {M[Pc(OBzCou)4] (M = 2H, Zn(II), Co(II); Bz: benzene; Cou: coumarin)} were synthesised. The novel chromogenic compounds were characterised by elemental analysis: 1H NMR, 13C NMR, MALDI-TOF, IR and UV–vis spectral data. The effect of coumarin substituents on the photophysical properties of metal-free (H2Pc) and zinc phthalocyanines (ZnPc) derivatives has been examined. Spectrophotometric measurements revealed that coumarin-substituted ZnPc derivatives were in the unaggregated form, whereas those of H2Pc species were in aggregated form. It means that substitution of coumarin derivative prevents the cluster formation in the presence of zinc ion in the centre of Pc.

Synthesis and photophysical properties of metallophthalocyanines substituted with a benzofuran based fluoroprobe

The synthesis, characterization and photophysical properties of the tetra- {6-(-benzofuran-2-carboxylate)-hexylthio} substituted copper(II), cobalt(II), manganese(III) and zinc (II) phthalocyanines, {M[Pc(β-S(CH(2))(6)OCOBz-Furan)(4)], which were derived from 6-(3,4-dicyanophenylthio)-hexyl-2-benzofuranate (BzF) (1-4) are reported for the first time. The new compounds have been synthesized and fully characterized by elemental analysis, FTIR, UV-vis, (1)H- and (13)C NMR, MS (Maldi-TOF). In this work, we also report the effects of peripherally bound BzF substituent on the photophysical properties of metallo phthalocyanine derivatives. The effects of changing the central metal ions on quantum yield are discussed. It was found that the substitution of BzF groups on the framework of phthalocyanines diminished the fluorescence quantum yield of these complexes depending on paramagnetic behavior of central metal atoms. In addition, central metal atoms like Co and Cu also caused to decrease in quantum yield of phthalocyanine backbone.

Development and characterization of ion-imprinted sol–gel-derived fluorescent film for selective recognition of mercury(II) ion

Abstract In this work, an ion-imprinted fluorescent sensor by combining sol–gel processing and spin coating was developed. Fluorescent functional silane was first synthesized and reacted with tetramethoxysilane to obtain sol–gel-derived materials and then used as a receptor for selective removal and sensing of Hg2+ in aqueous solution. Ion-imprinted material synthesized in the presence of Hg2+ was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, N2 adsorption–desorption analysis and thermogravimetric analysis by comparing with non-imprinted material obtained in the absence of Hg2+. Surface area, pore volume and diameter were analyzed from the profile of nitrogen adsorption. It was observed that fluorescent sol–gel film exhibits distinctive change in fluorescence emission upon interaction with Hg2+. Steady-state fluorescence experiments were performed for spectral characterization of the films, and the advancement of the reaction was defined. The shift in emission maxima and other spectral changes of the different matrices have been identified, and gelation time of sol–gel network was revealed by monitoring the emission of fluorescent silane in pre-gel solution. The corresponding selectivity factors of the imprinted fluorescent film toward Hg2+ against the other analogs were evaluated.Graphical Abstract

Fluorescence and Turbidimetry Study of Complexation of Human Serum Albumin with Polycations

Complexation of poly(N-ethyl-4-vinylpyridinium bromide) (PEVP) and poly(N-ethyl/cethyl-4-vinylpyridinium bromide) (PECVP) with human serum albumin (HSA) was studied by fluorescence spectroscopy and turbidimetric titration in dilute aqueous solutions. Solubility of polycation-HSA complexes depends on the initial concentrations and ratios of the components, pH, hydrophobic-hydrophilic balance of the macromolecules, and existence of low molecular salt (NaCl). A soluble interpolymer complex which is formed at low concentrations of polycation is insoluble at high polycation concentrations. The average fluorescence quantum yield of HSA decreases as polycation binds to the protein. The maximum reduction in emission intensity of HSA indicates the number of the HSA molecules bound per polymer chain. Quenching of HSA fluorescence by PECVP is decreased in the presence of NaCl at pH 7.0 but not at pH 4.3.

A vic -dioxime ligand bearing fluorescent coumarin moieties and its complexes; preparation, spectroscopy, and electrochemistry

The synthesis of a new vic-dioxime ligand, N,N′2-dihydroxy-O 1,O 2-bis(4-methyl-2-oxo-2H-chromen-7-yl)oxalimidamid (LH2) (1), bearing functional coumarins and its soluble mono- {Ni(II), Cu(II), Co(II)} and dinuclear {UO2(II)} complexes are presented. The fluorescence properties due to the 7-hydroxy-4-methylcoumarin fluorophore, which is conjugated with vic-dioxime that functions as the MN4 core of 1 and its complexes, are also reported. The formation of coordination complexes resulted in the blue shift in excitation spectrum and fluorescence quenching of 1. Both mononuclear {(LH)2M, M=Ni(II), Cu(II), and Co(II)} and homodinuclear {(LH)2(UO2)2(OH)2)} complexes have been obtained with metal : ligand ratios of 1 : 2 and 2 : 2, respectively. The characterizations of the new compounds were made by elemental analysis, 1H-NMR, FT-IR, UV-Vis, and LCMS data. Redox behavior of 1, involving oxime and coumarin moieties, and its complexes with Ni(II), Cu(II), Co(II) and UO2(II) were investigated by cyclic voltammetry. The comparison of the electrochemical behavior of 1 with its complexes enabled us to identify metal-, oxime- and coumarin-based signals.

Elucidation of Mercury Ion Binding Property of a New Aryl Amide Type Podand by Electrochemical and Fluorescence Measurements

Abstract A new aryl amide type podand (AAP), 1,8-bis(o-amidophenoxy)-3,6-dioxaoctane, was synthesized and its mercury ion binding property was elucidated by electrochemical and fluorescence measurements. The effects of supporting electrolyte, pH and scan rate on the electroreduction of AAP and on cyclic voltommogram of mercury ion were investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). It was observed that the complex formation between AAP and mercury ion exhibited pH-dependent behavior in different electrolyte solutions. Elucidation of such properties makes the AAP intriguing candidates as a modifying agent in sensor application for determination of mercury ion in mixture of aqueous solution.

Highly Stretchable DNA/Clay Hydrogels with Self-Healing Ability

We present mechanically strong and self-healable clay hydrogels containing 2-8 w/v % ds-DNA together with a synthetic biocompatible polymer, poly( N, N-dimethylacrylamide). Clay nanoparticles in the hydrogels act like a chemical cross-linker and promote their elastic behavior, whereas DNA contributes to their viscoelastic energy dissipation. The extent of mechanical hysteresis during cyclic tensile tests reveals that the strength of intermolecular bonds in DNA/clay hydrogels is in the range of the strength of hydrogen bonds. The hydrogels exhibit a high stretchability (up to 1500%) and a tensile strength between 20 and 150 kPa. They have the ability to self-heal, which is induced by heating the damaged gel samples above the melting temperature of ds-DNA. When comparing the mechanical properties of the hydrogels before and after healing, the healing efficiency is greater than 100%. We also demonstrate that ds-DNA molecules entrapped in the gel network undergoes thermal denaturation/renaturation cycles, leading to a further improvement in the mechanical properties of the hydrogels.