Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
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Article Citation - WoS: 195Optical Properties of Composites of Pmma and Surface-Modified Zincite Nanoparticles(American Chemical Society, 2007) Demir, Mustafa Muammer; Koynov, Kaloian; Akbey, Ümit; Bubeck, Christoph; Park, Insun; Lieberwirth, Ingo; Wegner, GerhardLocate full-text(opens in a new window)|Full Text(opens in a new window)|View at Publisher| Export | Download | Add to List | More... Macromolecules Volume 40, Issue 4, 20 February 2007, Pages 1089-1100 Optical properties of composites of PMMA and surface-modified zincite nanoparticles (Article) Demir, M.M.a, Koynov, K.a, Akbey, Ü.a, Bubeck, C.a, Park, I.ab, Lieberwirth, I.a, Wegner, G.a a Max Planck Institute for Polymer Research, Ackermannweg 10, D-55128 Mainz, Germany b Seoul National University, School of Chemistry, Korea, South Korea View references (65) Abstract Composites that show visible light transmittance, UV absorption, and moderately high refractive index, based on poly(methyl methacrylate) (PMMA) and zinc oxide (zincite, ZnO) nanoparticles, were prepared in two steps. First, surface-modified ZnO nanoparticles with 22 nm average diameter were nucleated by controlled precipitation via acid-catalyzed esterification of zinc acetate dihydrate with pentan-1-ol. The surface of growing crystalline particles was modified with tert-butylphosphonic acid (tBuPO3H2) in situ by monolayer coverage. Particle size and graft density of -PO3H 2 on the particle surface were controlled by the amount of surfactant applied to the reaction solution. Second, the surface-modified particles were incorporated into PMMA by in-situ bulk polymerization. Free radical polymerization was carried out in the presence of these particles using AIBN as initiator. Volume fraction (0) of the particles was varied from 0.10 to 7.76% (0.5 to 30 wt %). Although the particles are homogeneously dispersed in monomer, segregation of the individual particles upon polymerization was observed. Optical constants of the films ca. 2.0 μm including absorption and scattering efficiencies, indices of refraction, and dispersion constants were determined. The absorption coefficient at 350 nm increases linearly with ZnO, obeying Beer's law at low particle contents. However, it levels off toward a value of about 5000 cm-1 and shows a negative deviation at high concentrations because of aggregation of the individual particles. Waveguide propagation loss coefficients of the composite films were examined by prism coupling. A steep increase of the loss coefficient was found with a slope of 52 dB cm-1 vol %-1 as the volume fraction of the particle increases. The refractive index of the composites depends linearly on volume fraction of ZnO and varies from 1.487 to 1.507 (φ = 7.76%) at 633 nm. The dispersion of refractive index was found to be consistent with Cauchy's formula.Article Citation - WoS: 87Citation - Scopus: 108Synthesis and Characterization of Bentonite/Iron Nanoparticles and Their Application as Adsorbent of Cobalt Ions(Elsevier Ltd., 2010) Shahwan, Talal; Üzüm, Çağrı; Eroğlu, Ahmet Emin; Lieberwirth, IngoThis study reports the synthesis and characterization of iron nanoparticles in the presence of K10 bentonite. Introducing K10 during synthesis of iron nanoparticles resulted in a partial decrease in the aggregation of the nanoparticles. The dispersed nanoparticles showed a typical core–shell structure and were predominantly within the 10–60 nm size range. The composite adsorbent was tested for the removal of Co2+ ions in aqueous solution at various contact times, concentrations, pH, and repetitive loadings. The rate of adsorption was evaluated using first and second order rate equations. The adsorption was described by the Freundlich model. The adsorbent showed effective removal after re-use and the adsorption increased with increasing initial pH.Article Citation - WoS: 83Citation - Scopus: 97Characterization of the Uptake of Aqueous Ni2+ Ions on Nanoparticles of Zero-Valent Iron (nzvi)(Elsevier Ltd., 2009) Efecan, Nazlı; Shahwan, Talal; Eroğlu, Ahmet Emin; Lieberwirth, IngoThis study investigates the fixation of aqueous Ni2+ ions by nanoparticles of zero-valent iron (nZVI) prepared using the borohydride reduction method. The uptake of Ni2+ was tested under various experimental conditions like initial concentration, time, pH, and repetitive application of nZVI. Part of the experiments was devoted to comparing the extent of uptake of Ni2+ ions with those of Cu2+, Cd2+, Zn2+, and Sr2+ ions, which belong to a wide range of standard reduction potentials. Particle size analysis of nZVI in aqueous solution indicated that the material suffered extensive aggregation, much above the extent of aggregation known for dry nZVI. Nevertheless, nZVI showed fast uptake kinetics and very high uptake capacity. The overall results demonstrated the high fixation capability of nZVI towards the studied transition metal ions in aqueous solution. The same conclusion is, however, not valid for the removal of Sr2+ ions.Article Citation - WoS: 163Citation - Scopus: 187Application of Zero-Valent Iron Nanoparticles for the Removal of Aqueous Co2+ Ions Under Various Experimental Conditions(Elsevier Ltd., 2008) Üzüm, Çağrı; Shahwan, Talal; Eroğlu, Ahmet Emin; Lieberwirth, Ingo; Scott, Thomas B.; Hallam, Keith R.Nanosized zero-valent iron (nZVI) is increasingly gaining interest as an efficient sorbent for various types of aqueous pollutants. In this study, nZVI was synthesised by the borohydride reduction method, characterised and then examined for the removal of aqueous Co2+ ions over a wide range of concentrations, from 1 to 1000 mg/L. The size of nZVI particles was predominantly within the range of 20–80 nm, and only limited oxidation was observed in samples aged for a period of 2 months. The experiments investigated the effects of V/m ratio, concentration, contact time, repetitive loading, pH and aging on the extent of retardation of Co2+ ions. Iron nanoparticles demonstrated very rapid uptake and large capacity for the removal of Co2+ ions. Effective uptake was observed even after a number of repetitive trials. The extent of Co2+ uptake increased with the increasing pH. X-ray photoelectron spectroscopy (XPS) indicate that the fixation of Co2+ ions takes place through the interaction of these ions with the oxohydroxyl groups on the iron nanoparticle surfaces in addition to spontaneous precipitate formation at high loadings.