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Publication Metadata only 3D printed poly(lactic acid) scaffolds modified with chitosan and hydroxyapatite for bone repair applications(Elsevier, 2020) N/A; N/A; N/A; N/A; Department of Chemistry; Department of Chemical and Biological Engineering; Department of Chemistry; Nazeer, Muhammad Anwaar; Önder, Özgün Can; Sevgili, İlkem; Yılgör, Emel; Kavaklı, İbrahim Halil; Yılgör, İskender; PhD Student; PhD Student; PhD Student; Researcher; Faculty Member; Faculty Member; Department of Chemical and Biological Engineering; Department of Chemistry; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Sciences; College of Engineering; College of Sciences; N/A; N/A; N/A; N/A; 40319; 241813D printed poly(lactic acid) (PLA) scaffolds surface modified with chitosan (CS) and hydroxyapatite (HA) to produce a novel bioactive composite scaffold is reported. Excellent mechanical properties of PLA, the bioactivity of CS, and osteogenic characteristics of HA are combined to fabricate composite scaffolds using a simple desktop 3D printer. Scaffolds were characterized through attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy, X-ray diffraction (XRD) and water contact angle measurements before and after modification. Formic acid was used as a solvent to prepare stable CS/HA dispersions and was found to be a suitable solvent for producing PLA/CS/HA composites. Surface properties of modified scaffolds were superior in terms of hydrophilicity and bioactivity, which resulted in enhanced attachment and proliferation of human osteosarcoma cells in vitro compared to the unmodified PLA scaffolds.Publication Metadata only 3D printing of cytocompatible gelatin-cellulose-alginate blend hydrogels(Wiley-V C H Verlag Gmbh, 2020) Erkoc, Pelin; Uvak, Ileyna; Odeh, Yazan Nitham; Akdogan, Ozan; Odeh, Yazan Nitham; Akdogan, Ozan; N/A; Department of Chemistry; Department of Chemical and Biological Engineering; Nazeer, Muhammad Anwaar; Batool, Syeda Rubab; Kızılel, Seda; PhD Student; Researcher; Faculty Member; Department of Chemistry; Department of Chemical and Biological Engineering; Graduate School of Sciences and Engineering; College of Sciences; College of Engineering; N/A; N/A; 283763D bioprinting of hydrogels has gained great attention due to its potential to manufacture intricate and customized scaffolds that provide favored conditions for cell proliferation. Nevertheless, plain natural hydrogels can be easily disintegrated, and their mechanical strengths are usually insufficient for printing process. Hence, composite hydrogels are developed for 3D printing. This study aims to develop a hydrogel ink for extrusion-based 3D printing which is entirely composed of natural polymers, gelatin, alginate, and cellulose. Physicochemical interactions between the components of the intertwined gelatin-cellulose-alginate network are studied via altering copolymer ratios. The structure of the materials and porosity are assessed using infrared spectroscopy, swelling, and degradation experiments. The utility of this approach is examined with two different crosslinking strategies using glutaraldehyde or CaCl2. Multilayer cylindrical structures are successfully 3D printed, and their porous structure is confirmed by scanning electron microscopy and Brunauer-Emmett-Teller surface area analyses. Moreover, cytocompatibility of the hydrogel scaffolds is confirmed on fibroblast cells. The developed material is completely natural, biocompatible, economical, and the method is facile. Thus, this study is important for the development of advanced functional 3D hydrogels that have considerable potential for biomedical devices and artificial tissues.Publication Metadata only [BMIM] [PF6] incorporation doubles CO2 selectivity of ZIF-8: elucidation of interactions and their consequences on performance(Amer Chemical Soc, 2016) N/A; N/A; N/A; N/A; N/A; Department of Chemical and Biological Engineering; Department of Chemical and Biological Engineering; Kınık, Fatma Pelin; Altıntaş, Çiğdem; Balcı, Volkan; Koyutürk, Burak; Uzun, Alper; Keskin, Seda; Master Student; Researcher; PhD Student; Master Student; Faculty Member; Faculty Member; Department of Chemical and Biological Engineering; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; N/A; N/A; N/A; N/A; 59917; 40548Experiments were combined with atomically detailed simulations and density functional theory (DFT) calculations to understand the effect of incorporation of an ionic liquid (IL), 1-n-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]), into a metal organic framework (MOF with a zeolitic imidazolate framework), ZIF-8, on the CO2 separation performance. The interactions between [BMIM] [PF6] and ZIF-8 were examined in deep detail, and their consequences on CO2/CH4, CO2/N-2, and CH4/N-2 separation have been elucidated by using experimental measurements complemented by DFT calculations and atomically detailed simulations. Results suggest that IL-MOF interactions strongly affect the gas affinity of materials at low pressure, whereas available pore volume plays a key role for gas adsorption at high pressures. Direct interactions between IL and MOF lead to at least a doubling of CO2/CH4 and CO2/N-2 selectivities of ZIF-8. These results provide opportunities for rational design and development of IL-incorporated MOFs with exceptional selectivity for target gas separation applications.Publication Open Access A new class of porous materials for efficient CO2 separation: ionic liquid/graphene aerogel composites(Elsevier, 2021) Department of Chemical and Biological Engineering; N/A; Department of Chemistry; Zeeshan, Muhammad; Yalçın, Kaan; Keskin, Seda; Uzun, Alper; Öztuna, Feriha Eylül Saraç; Ünal, Uğur; PhD Student; Faculty Member; Faculty Member; Department of Chemical and Biological Engineering; Department of Chemistry; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Graduate School of Sciences and Engineering; College of Engineering; College of Sciences; N/A; N/A; 40548; 59917; N/A; 42079Here, we report a new post-synthesis modification strategy for functionalizing reduced graphene aerogels (rGAs) towards an exceptional CO2 separation performance. 1-N-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) was impregnated on a rGA, prepared by reducing GA at 700 degrees C, at various ionic liquid (IL) loadings of 5, 10, 30, and 50 wt%. The resulting composites were characterized in deep detail by X-ray photoelectron spectroscopy, X-ray diffraction, N-2 physical adsorption measurements, scanning electron microscopy, Fourier transform infrared and Raman spectroscopies, and thermogravimetric analysis. Results indicated the presence of interactions between the rGA surface and the anion of the IL, potentially improving the CO2 affinity. Volumetric gas adsorption measurements using these materials showed that the deposition of [BMIM][PF6] on rGA surface at an IL loading of 50 wt% boosts the CO2/CH4 selectivity by more than 20-times, exceeding an absolute value of 120, a remarkably higher CO2/CH4 selectivity compared to that of other functionalized materials under similar operating conditions. Tunability of both the IL structure and the surface characteristics of rGA offer a tremendous degree of flexibility for the rational design of these IL/rGA composites towards high performance in gas separation applications.Publication Metadata only A new venue toward predicting the role of hydrogen embrittlement on metallic materials(Springer, 2016) N/A; N/A; Department of Chemical and Biological Engineering; Department of Mechanical Engineering; Bal, Burak; Şahin, İbrahim; Uzun, Alper; Canadinç, Demircan; PhD Student; PhD Student; Faculty Member; Faculty Member; Department of Chemical and Biological Engineering; Department of Mechanical Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; N/A; N/A; 59917; 23433This paper presents a new crystal plasticity formulation to predict the role of hydrogen embrittlement on the mechanical behavior of metallic materials. Specifically, a series of experiments were carried out to monitor the role of hydrogen interstitial content on the uniaxial tensile deformation response of iron alloyed with hydrogen, and the classical Voce hardening scheme was modified to account for the shear stresses imposed on arrested dislocations due to the surrounding hydrogen interstitials. The proposed set of physically grounded crystal plasticity formulations successfully predicted the deformation response of iron in the presence of different degrees of hydrogen embrittlement. Moreover, the combined experimental and modeling effort presented herein opens a new venue for predicting the alterations in the performance of metallic materials, where the hydrogen embrittlement is unavoidable.Publication Metadata only Adsorption and transport of CH4, CO2, H-2 mixtures in a bio-MOF material from molecular simulations(Amer Chemical Soc, 2011) N/A; N/A; Department of Chemical and Biological Engineering; Atcı, Erhan; Eruçar, İlknur; Keskin, Seda; Master Student; PhD Student; Faculty Member; Department of Chemical and Biological Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 260094; 40548Accurate description of gas adsorption and diffusion in nanoporous materials is crucial in envisioning new materials for adsorption-based and membrane-based gas separations. This study provides the first information about the equilibrium and transport properties of different gas mixtures in a bio-metal organic framework (bio-MOF). Adsorption isotherms and self-diffusivity coefficients of CH4, CO2, H-2, and their binary mixtures in bio-MOF-11 were computed using grand canonical Monte Carlo and equilibrium molecular dynamics simulations. Results showed that bio-MOF-11 exhibits significantly higher adsorption selectivity for CO2 over CH4 and H-2 than the widely studied MOFs. Bio-MOF-11 outperforms several isoreticular MOFs, traditional zeolites, and zeolite imidazolate frameworks in membrane-based separations of CH4/H-2, CO2/CH4, and CO2/H-2 mixtures due to its high gas permeability and permeation selectivity. The methods used in this work will assess the potential of bio-MOFs in gas separations and accelerate development of new bio-MOFs for targeted applications by providing molecular insights into adsorption transport of gas mixtures.Publication Metadata only Adsorption, diffusion, and separation of CH4/H-2 mixtures in covalent organic frameworks: molecular simulations and theoretical predictions(amer Chemical Soc, 2012) N/A; Department of Chemical and Biological Engineering; Keskin, Seda; Faculty Member; Department of Chemical and Biological Engineering; College of Engineering; 40548Grand canonical Monte Carlo and equilibrium molecular dynamics simulations were used to compute adsorption isotherms and self-diffusivities of CH4/H2 mixtures at various compositions in three representative covalent organic frameworks (COFs). Several properties of COFs such as adsorption selectivity, working capacity, diffusion selectivity, gas permeability, and membrane selectivity were evaluated and were compared with metal organic frameworks (MOFs), zeolites, zeolite imidazolate frameworks (ZIFs), and carbon nanotubes. Results showed that COF-6 outperforms traditional zeolites CHA, LTA, and ITQ-29 and MOFs IRMOF-1, CuBTT, and MOF-177 in adsorption-based CH4 selectivity. Membrane selectivities of COF-5, COF-6, and COF-10 were found to be higher than those of zeolites and similar to ZIFs and MOFs. Adsorption isotherms and diffusivities of CH4/H2 mixtures in the pores of COF-6 were computed using both atomically detailed simulations and theoretical correlations. Results showed that theoretical correlations based on single component adsorption and diffusion data can be used to accurately predict mixture adsorption and diffusion of gases in COFs.Publication Metadata only Advances in constraint theories of rubber-like elasticity of polymers(Pergamon-Elsevier Science Ltd, 2010) Department of Chemical and Biological Engineering; Erman, Burak; Faculty Member; Department of Chemical and Biological Engineering; College of Engineering; 179997Advances in the constraint theories of rubber elasticity during the past few years, based on the constrained junction, tube, and slip-link models, are cited and discussed. (C) 2009 Elsevier Ltd. All rights reserved.Publication Metadata only Aerogel-copper nanocomposites prepared using the adsorption of a polyfluorinated complex from supercritical CO2(Springer, 2012) Kostenko, Svetlana O.; Kurykin, Michael A.; Khrustalev, Victor N.; Khokhlov, Alexei R.; Zhang, Lichun; Aindow, Mark; Department of Chemical and Biological Engineering; Department of Chemical and Biological Engineering; Bozbağ, Selmi Erim; Erkey, Can; Researcher; Faculty Member; Department of Chemical and Biological Engineering; College of Engineering; College of Engineering; N/A; 29633A supercritical deposition method has been used to synthesize aerogel-copper nanocomposites. Carbon, resorcinol-formaldehyde, and silica aerogels (CAs, RFAs, and SAs) were impregnated with a new polyfluorinated copper precursor (CuDI6), which has a high solubility in supercritical carbon dioxide (scCO(2)). Adsorption isotherms of CuDI6 onto various aerogels from scCO(2) were determined at 35 degrees C and 10.6 MPa using a batch method which is based on the measurement of the fluid phase concentration. The relative affinity between CuDI6 and different aerogels changed in the following order: CA > RFA > SA. The effect of temperature on the adsorption isotherms for the CuDI6-CO2-CA system was also studied at 35 and 55 degrees C and at a CO2 density of 736.1 kg/m(3). The CuDI6 uptake at a particular CuDI6 concentration increased with increasing temperature. Adsorbed CuDI6 was found to convert into Cu and Cu/Cu2O nanoparticles on the aerogel supports after chemical or thermal treatments at ambient pressure and at temperatures ranging from 200 to 400 degrees C.Publication Metadata only An all-aqueous approach for physical immobilization of PEG-lipid microgels on organoid surfaces(Elsevier, 2020) N/A; N/A; Department of Chemical and Biological Engineering; Akolpoğlu, Mükrime Birgül; İnceoğlu, Yasemin; Kızılel, Seda; Master Student; Master Student; Faculty Member; Department of Chemical and Biological Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; 28376Emulsion-based generation of hydrogel particles has been widely explored for numerous applications in fields such as biomedical, food, and drug delivery. Water-in-water emulsion (w/w) is an organic solvent-free approach and exploits solely aqueous media to generate nano- or micropartides. This strategy is environment-friendly and favorable for biomedical applications where biocompatibility is the ultimate criterion. Hence, PEG-based microgels can be synthesized with desired size and functionality using w/w emulsion technique. To estimate the influence of emulsification parameters on size and stability of PEG-lipid microgels, optimizations using three independent input variables were carried out: (i) ultrasonication power, (ii) ultrasonication duration, and (iii) duration of light exposure. Physical immobilization of microgels on islet-organoids was achieved through hydrophobic interactions. Cell function and viability were assessed thoroughly after microgel immobilization. Microgel size is dependent on ultrasonication parameters and microgel stability is vastly determined by the duration of light exposure. Immobilization of microgels with 5 mM lipid moiety promoted coating of islet-organoids. Coated organoids retained their function and viability without significant adverse effects. This is important for understanding fundamental aspects of PEG-lipid microgels using w/w emulsion, useful for possible drug/gene delivery applications to increase treatment efficiency and ultimately lead to clinical translation of PEG microgels for biomedical applications.