Researcher:
Ülker, Zeynep

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PhD Student

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Zeynep

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Ülker

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Ülker, Zeynep

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2013 - 20177

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Researcher Of Publications: search.filters.isAuthorOfPublication.96d16259-731d-4640-83c3-ae1aa0a33701

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Now showing 1 - 7 of 7
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    Novel nanostructured composites of silica aerogels with a metal organic framework
    (Elsevier, 2013) N/A; N/A; Department of Chemical and Biological Engineering; Department of Chemical and Biological Engineering; Department of Chemical and Biological Engineering; Ülker, Zeynep; Eruçar, İlknur; Keskin, Seda; Erkey, Can; PhD Student; PhD Student; Faculty Member; Faculty Member; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; 262388; 260094; 40548; 29633
    Novel nanostructured composites of silica aerogel with Cu-BTC were synthesized using a slightly modified version of the conventional sol-gel method used to synthesize silica aerogels. The composite materials had monolithic structures with blue color consisting of well dispersed microporous domains of Cu-BTC in the mesoporous inorganic silica aerogel network. The Cu-BTC content in the composites ranged from 5 to 30 weight percent and the total surface area of the composites ranged from 1025 to 1138 m(2)/g. The microporosity of the composites increased with the increasing amount of Cu-BTC indicating that the micropores of Cu-BTC were accessible and functional. XRD analysis indicated that Cu-BTC retained its crystal structure in the composite despite being immersed in a solution containing water, ethanol and tetraethylorthosilicate. Additionally, it was observed that increasing Cu-BTC content caused a decrease in the average desorption pore radius with a wider pore size distribution. Nitrogen adsorption isotherms for composites could be predicted using the experimentally obtained pure component isotherm for the silica aerogel, theoretically obtained isotherm for Cu-BTC and the weight fractions of the components within the composite material.
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    An emerging platform for drug delivery: aerogel based systems
    (Elsevier, 2014) N/A; Department of Chemical and Biological Engineering; Department of Chemical and Biological Engineering; Ülker, Zeynep; Erkey, Can; PhD Student; Faculty Member; Graduate School of Sciences and Engineering; College of Engineering; 262388; 29633
    Over the past few decades, advances in "aerogel science" have provoked an increasing interest for these materials in pharmaceutical sciences for drug delivery applications. Because of their high surface areas, high porosities and open pore structures which can be tuned and controlled by manipulation of synthesis conditions, nanostructured aerogels represent a promising class of materials for delivery of various drugs as well as enzymes and proteins. Along with biocompatible inorganic aerogels and biodegradable organic aerogels, more complex systems such as surface functionalized aerogels, composite aerogels and layered aerogels have also been under development and possess huge potential. Emphasis is given to the details of the aerogel synthesis and drug loading methods as well as the influence of synthesis parameters and loading methods on the adsorption and release of the drugs. Owing to their ability to increase the bioavailability of low solubility drugs, to improve both their stability and their release kinetics, there are an increasing number of research articles concerning aerogels in different drug delivery applications. This review presents an up to date overview of the advances in all kinds of aerogel based drug delivery systems which are currently under investigation.
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    Three-dimensional optofluidic waveguides in hydrophobic silica aerogels via supercritical fluid processing
    (Elsevier, 2013) Jonas, Alexandr; Department of Chemical and Biological Engineering; N/A; N/A; Department of Chemical and Biological Engineering; Department of Physics; Department of Physics; Department of Chemical and Biological Engineering; Department of Physics; Department of Chemical and Biological Engineering; Eris, Gamze; Şanlı, Deniz; Ülker, Zeynep; Bozbağ, Selmi Erim; Kiraz, Alper; Erkey, Can; Researcher; Researcher; PhD Student; Researcher; Other; Faculty Member; Faculty Member; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); College of Engineering; N/A; Graduate School of Sciences and Engineering; College of Engineering; College of Sciences; College of Sciences; College of Engineering; N/A; N/A; 262388; N/A; N/A; 22542; 29633
    Optofluidic components enable flexible routing and transformations of light beams in integrated lab-on-a-chip systems with the use of carefully shaped fluid parcels. For structural integrity reasons, the working fluid is typically contained within a solid-material chip. One of the outstanding challenges in optofluidics is the preparation and processing of optofluidic waveguides. These require solid cladding materials that are sufficiently strong to contain the fluid while possessing optical properties that allow efficient confinement of light within fluidic channels. Here, we report on a new technique to obtain liquid-core optofluidic waveguides based on total internal reflection of light in three-dimensional water-filled channels embedded in hydrophobic silica aerogel. To form the channels, we employ a fiber made of cage-like silicon-oxygen compound - trifluoropropyl polyhedral oligomeric silsesquioxane (trifluoropropyl PUSS) - which has high solubility in supercritical CO2 (scCO(2)). A U-shaped fiber made of trifluoropropyl PUSS is obtained by melt/freeze processing of PUSS powder and subsequently placed in a silicate sol. After gelation of the sol and aging of the gel, scCO(2) extraction is used to dry the wet gel and extract the POSS fiber, yielding a dry silica aerogel with a U-shaped empty channel inside it. Finally, the silanol groups at the surface of the aerogel are reacted with hexamethyldisilazane (HMDS) in the presence of scCO(2) to render the aerogel surface hydrophobic and the channel is filled with water. We demonstrate efficient waveguiding by coupling light into the water-filled channel and monitoring the channel output. The presented procedure opens up new possibilities for creating complex three-dimensional networks of liquid channels in aerogels for optofluidic applications. (C) 2012 Elsevier B.V. All rights reserved.
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    An advantageous technique to load drugs into aerogels: gas antisolvent crystallization inside the pores
    (Elsevier Science Bv, 2017) N/A; Department of Chemical and Biological Engineering; Department of Chemical and Biological Engineering; Ülker, Zeynep; Erkey, Can; PhD Student; Faculty Member; Graduate School of Sciences and Engineering; College of Engineering; 262388; 29633
    Over the past few years, both organic and inorganic nanoporous aerogels have shown a great promise as drug delivery vehicles. Different methods are utilized to load drugs into aerogels such as the addition of the drug to the reaction mixture in one of the steps before the gel formation or by supercritical deposition to the aerogels. These techniques have disadvantages such as possible reactions of pharmaceutical compounds with reactants used to form gels and low solubility of pharmaceutical compounds in supercritical carbon dioxide (scCO(2)). An alternative technique is to load the drug after gel formation by contacting the gel with a solution of the drug. The drug diffuses into the liquid inside the pores. When this drug-loaded gel is subjected to supercritical drying, scCO(2) not only removes the solvent from the pores but also acts as an antisolvent, which causes the precipitation of the drug in the pores of the aerogel. This is similar to the gas antisolvent crystallization (GAS) process but in this case the process takes place inside the pores. In this study, this technique was used to load paracetamol into silica aerogels. The factors affecting the amount and distribution of the drug inside the aerogel matrix were investigated and a mathematical model to account for the movement of paracetamol inside the pores during supercritical drying leading to a varying drug concentration in the matrix with position was developed. It was concluded that high initial concentrations resulted in more homogeneous drug distributions. Moreover, XRD analysis demonstrated that paracetamol was in crystalline form. The process enables higher amount of loadings than conventional systems and also offers an advantage as it combines two processes such as drying and loading in a single one reducing the time and the operating expenses.
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    Monolithic composites of silica aerogel with poly(methyl vinyl ether) and the effect of polymer on supercritical drying
    (Elsevier, 2015) N/A; N/A; N/A; Department of Chemical and Biological Engineering; Department of Electrical and Electronics Engineering; Department of Chemical and Biological Engineering; Department of Electrical and Electronics Engineering; Özbakır, Yaprak; Ülker, Zeynep; Erkey, Can; PhD Student; PhD Student; Faculty Member; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; 262388; 29633
    Novel monolithic and crack-free poly(methyl vinyl ether) (PMVE)-silica aerogel composites were synthesized using a modified sol gel procedure. The presence of PMVE in solid network of the composite samples was confirmed by a variety of techniques including IR spectroscopy, TGA and BET. Extraction of ethanol from alcogel composite rods using scCO(2) was investigated both by experiments and simulations. Partial differential equations representing mass transfer within the composite alcogel phase and in the flowing scCO(2) phase were developed and solved using finite difference method. Mass of ethanol removed from the samples as a function of time were found to be in good agreement with model results using mass transfer coefficients regressed from the experimental data. Effect of the polymer content on the drying could be estimated by taking into account of porosity change with polymer incorporation. Drying time of the alcogel increased with increasing weight fraction of polymer in the silica network and gel thickness.
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    Applications of aerogels and their composites in energy-related technologies
    (Elsevier, 2014) N/A; N/A; Department of Chemical and Biological Engineering; Department of Chemical and Biological Engineering; Ülker, Zeynep; Şanlı, Deniz; Erkey, Can; PhD Student; PhD Student; Faculty Member; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; 262388; N/A; 29633
    Aerogels were first synthesized in 1932 and are promising materials for a variety of energy-related applications. Their intriguing and adjustable properties such as high surface areas, sharp pore size distributions, low thermal conductivities, and high sorption capacities will continue to make these materials attractive for scientists and researchers from a wide variety of disciplines.
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    PublicationOpen Access
    A novel hybrid material: an inorganic silica aerogel core encapsulated with a tunable organic alginate aerogel layer
    (Royal Society of Chemistry (RSC), 2014) Department of Chemical and Biological Engineering; Department of Chemical and Biological Engineering; Ülker, Zeynep; Erkey, Can; PhD Student; Faculty Member; Graduate School of Sciences and Engineering; College of Engineering; N/A; 29633
    A novel layered material consisting of a silica aerogel core encapsulated by an alginate aerogel layer was developed. The components of the hybrid aerogel had the high surface area and high porosity of pure aerogels which should lead to development of new layered systems for a wide variety of applications.