Chemistry / Kimya
Permanent URI for this collectionhttps://hdl.handle.net/11147/4072
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Article Citation - WoS: 6Citation - Scopus: 7Utilization of Electrospun Polystyrene Membranes as a Preliminary Step for Rapid Diagnosis(John Wiley and Sons Inc., 2016) Işık, Tuğba; Horzum, Nesrin; Yıldız, Ümit Hakan; Liedberg, Bo; Demir, Mustafa MuammerRecent advances in clinical practice drive deoxyribonucleic acid (DNA) as an important class of biomarker. Monitoring the change in their concentration suggests the initiation and/or progression of various disorders. However, low quantity of DNA biomarkers in body fluids requires a delicate isolation methodology that provides efficient separation and easy handling. This study describes a newer-generation separation technology relying on electrospun fibers of sub-micrometer diameter of a commodity polymer for DNA biomarkers in simulative serum. Fibrous polystyrene membranes are prepared by electrospinning and they are subjected to post-modification with Au. The composite membranes may provide a convenient environment for the removal of bovine serum albumin (BSA) from BSA and DNA mixtures. The eluent can be used as an efficient tool for detection of DNA biomarkers associated with diagnosis of numerous life-threatening diseases.Letter Citation - WoS: 46Citation - Scopus: 53A Characterization Study of Some Aspects of the Adsorption of Aqueous Co2+ Ions on a Natural Bentonite Clay(Elsevier Ltd., 2006) Shahwan, Talal; Erten, Hasan N.; Ünügür, S.The natural bentonite used in this study contained montmorillonite in addition to low cristobalite. The uptake of aqueous Co2+ ions was investigated as a function of time, concentration, and temperature. In addition, the change in the interlayer space of montmorillonite was analyzed using XRPD, and the distribution of fixed Co2+ ions on the heterogeneous clay surface was recorded using EDS mapping. The sorbed amount of Co2+ appeared to closely follow Freundlich isotherm, with the sorption process showing apparent endothermic behavior. The relevance of the apparent Δ Ho values is briefly discussed. Analysis of the Co-sorbed bentonite samples using SEM/EDS showed that the montmorillonite fraction in the mineral was more effective in Co2+ fixation than the cristobalite fraction. XRPD analysis demonstrated that the interlayer space of montmorillonite was slightly modified at the end of sorption.Article Citation - WoS: 211Citation - Scopus: 246A Radiotracer Study of the Adsorption Behavior of Aqueous Ba2+ Ions on Nanoparticles of Zero-Valent Iron(Elsevier Ltd., 2007) Çelebi, O.; Üzüm, Çağrı; Shahwan, Talal.; Erten, Hasan NRecently, iron nanoparticles are increasingly being tested as adsorbents for various types of organic and inorganic pollutants. In this study, nanoparticles of zero-valent iron (NZVI) synthesized under atmospheric conditions were employed for the removal of Ba2+ ions in a concentration range 10-3 to 10-6 M. Throughout the study, 133Ba was used as a tracer to study the effects of time, concentration, and temperature. The obtained data was analyzed using various kinetic models and adsorption isotherms. Pseudo-second-order kinetics and Dubinin-Radushkevich isotherm model provided the best correlation with the obtained data. Observed thermodynamic parameters showed that the process is exothermic and hence enthalpy-driven.Article Citation - WoS: 47Effect of Filler Amount on Thermoelastic Properties of Poly (dimethylsiloxane) Networks(Elsevier Ltd., 2005) Demir, Mustafa Muammer; Menceloğlu, Yusuf Z.; Erman, BurakEnd-linked poly(dimethylsiloxane) (PDMS) networks were prepared in the presence of fumed silica particles with hydroxyl groups at their surfaces. The silica particles were introduced into the polymer solution prior to end-linking. Hydroxyl ended PDMS chains were end-linked via the tetra functional crosslinker, tetraethoxysilane. The filler content varied in the range 0-5 wt%. Atomic Force Microscopy was used to image and characterize the silica particles. Swelling, stress-strain and thermoelasticity experiments were performed. The temperature coefficient and the energetic part of the force in uniaxial extension are found to increase with increasing silica amount. This observation is ascribed to effects contributed possibly by the adsorption layer around the silica particles.Article Citation - WoS: 109Citation - Scopus: 124Chitosan Fiber-Supported Zero-Valent Iron Nanoparticles as a Novel Sorbent for Sequestration of Inorganic Arsenic(Royal Society of Chemistry, 2013) Horzum Polat, Nesrin; Demir, Mustafa Muammer; Nairat, Muath; Shahwan, TalalThis study proposes a new sorbent for the removal of inorganic arsenic from aqueous solutions. Monodispersed nano zero-valent iron (nZVI) particles were nucleated at the surface of electrospun chitosan fibers (average fiber diameter of 195 ± 50 nm) by liquid phase reduction of FeCl3 using NaBH4. The material was characterized using SEM, TGA, XPS, XRD, and FTIR. The diameter of iron nanoparticles was found to vary between 75-100 nm. A set of batch experiments were carried out to elucidate the efficiency of the composite sorbent toward fixation of arsenite and arsenate ions. The ion concentrations in the supernatant solutions were determined using inductively coupled plasma-mass spectrometry (ICP-MS). The results revealed that the chitosan fiber supported nZVI particles is an excellent sorbent material for inorganic arsenic uptake at concentrations ranging from 0.01 to 5.00 mg L -1 over a wide range of pH values. Based on XPS analysis, As(iii) was found to undergo oxidation to As(v) upon sorption, while As(v) retained its oxidation state. By virtue of the successful combination of the electrospun fibers' mechanical integrity and the large reactivity of dispersed nZVI particles, the applicability of the resulting sorbent material in arsenic sorption holds broad promise.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.