Browsing by Subject "Porosity"

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    ItemOpen Access
    Bacteria encapsulated electrospun nanofibrous webs for remediation of methylene blue dye in water
    (Elsevier, 2017-04) Sarioglu O.F.; Keskin, N. O. S.; Celebioglu A.; Tekinay, T.; Uyar, Tamer
    In this study, preparation and application of novel biocomposite materials that were produced by encapsulation of bacterial cells within electrospun nanofibrous webs are described. A commercial strain of Pseudomonas aeruginosa which has methylene blue (MB) dye remediation capability was selected for encapsulation, and polyvinyl alcohol (PVA) and polyethylene oxide (PEO) were selected as the polymer matrices for the electrospinning of bacteria encapsulated nanofibrous webs. Encapsulation of bacterial cells was monitored by scanning electron microscopy (SEM) and fluorescence microscopy, and the viability of encapsulated bacteria was checked by live/dead staining and viable cell counting assay. Both bacteria/PVA and bacteria/PEO webs have shown a great potential for remediation of MB, yet bacteria/PEO web has shown higher removal performances than bacteria/PVA web, which was probably due to the differences in the initial viable bacterial cells for those two samples. The bacteria encapsulated electrospun nanofibrous webs were stored at 4 °C for three months and they were found as potentially storable for keeping encapsulated bacterial cells alive. Overall, the results suggest that electrospun nanofibrous webs are suitable platforms for preservation of living bacterial cells and they can be used directly as a starting inoculum for bioremediation of water systems.
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    ItemOpen Access
    Cornea engineering on polyester carriers
    (John Wiley & Sons, Inc., 2006) Zorlutuna, P.; Tezcaner, A.; Kiyat, I.; Aydınlı, Atilla; Hasirci, V.
    In this study, biodegradable polyester based carriers were designed for tissue engineering of the epithelial and the stromal layers of the cornea, and the final construct was tested in vitro. In the construction of the epithelial layer, micropatterned films were prepared from blends of biodegradable and biocompatible polyesters of natural (PHBV) and synthetic (P(L/DL)LA) origin, and these films were seeded with D407 (retinal pigment epithelial) cells. To improve cell adhesion and growth, the films were coated with fibronectin. To serve as the stromal layer of the cornea, highly porous foams of P(L/DL)LA-PHBV blends were seeded with 3T3 fibroblasts. Cell numbers on the polyester carriers were significantly higher than those on the tissue culture polystyrene control. The cells and the carriers were characterized scanning electron micrographs showed that the foam was highly porous and the pores were interconnected. 3T3 Fibroblasts were distributed quite homogeneously at the seeding site, but probably because of the high thickness of the carrier (∼6 mm); they could not sufficiently populate the core (central parts of the foam) during the test duration. The D407 cells formed multilayers on the micropatterned polyester film. Immunohistochemical studies showed that the cells retained their phenotype during culturing; D407 cells formed tight junctions characteristic of epithelial cells, and 3T3 cells deposited collagen type I into the foams. On the basis of these results, we concluded that the micropatterned films and the foams made of P(L/DL)LA-PHBV blends have a serious potential as tissue engineering carriers for the reconstruction of the epithelial and stromal layers of the cornea.
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    Electrospun Fe2O3 entrenched SiO2 supported N and S dual incorporated TiO2 nanofibers derived from mixed polymeric template/surfactant: enriched mesoporosity within nanofibers, effective charge separation, and visible light photocatalysis activity
    (American Chemical Society, 2019) Pradhan, Amaresh C.; Uyar, Tamer
    The α-Fe2O3 promoted and SiO2 supported N and S dual incorporated TiO2 nanofibers (FeSiNST NFs) along with neat oxide NFs have been synthesized by electrospinning via sol–gel. The keen approach is that mixed polyvinylpyrrolidone (PVP) as template and cetyltrimethylammonium bromide (CTAB) as surfactant are responsible for the creation of mesoporosity within NFs. The photoluminescence (PL) spectrum and UV–visible diffuse reflectance spectroscopic (DRS) result revealed the role of α-Fe2O3 as catalytic promoter in FeSiNST NFs by suppressing electron–hole (e––h+) recombination, red shifting, and oxygen vacancies (Ovs). The design of FeSiNST NFs by combining with SiO2 as catalytic support and N and S as visible light absorbers in TiO2, beautifies the present study. The high photocurrent (3.2 mA/cm2), high Efb value (−1.0 V), and low Rct value (∼74 Ω) support the enhanced photocatalysis (photoreduction and photodegradation) by FeSiNST in visible light. Charge transfer phenomena, Ovs, mesoporosity, and separation of e––h+ are the vital factors for an effective photocatalysis achievement.
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    Poly-cyclodextrin cryogels with aligned porous structure for removal of polycyclic aromatic hydrocarbons (PAHs) from water
    (Elsevier, 2017-08) Topuz, F.; Uyar, Tamer
    Cyclodextrins (CDs) are sugar-based cyclic oligosaccharides, which form inclusion complexes with small guest molecules through their hydrophobic cavity. Here we successfully synthesized highly porous poly-cyclodextrin (poly-CD) cryogels, which were produced under cryogenic conditions by the cross-linking of amine-functional CDs with PEG-based diepoxide cross-linker. The poly-CD cryogels showed aligned porous network structures owing to the directional freezing of the matrix, of which the pore size and architecture exposed variations depending on the composition of the reactants. The cryogels were employed for the removal of genotoxic polycyclic aromatic hydrocarbons (PAHs) from aqueous solutions. They reached PAH sorption capacities as high as 1.25 mg PAH per gram cryogel. This high sorption performance is due to interactions between PAHs and the complete swollen network, and thus, is not restricted by interfacial adsorption. Given that the hydrophilic nature of the components, the sorption performance could only be attributed to the inclusion complex formation of CDs with PAH molecules. The poly-CD cryogels could be recycled with an exposure to ethanol and reused without any significant loss in the sorption capacity of PAHs.
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    Preparation, characterization, and investigation of H2 storage capacities of Pruussian Blue analogues
    (2015) Altınsoy, Büşra
    A convenient and efficient hydrogen storage system is a research challenge since hydrogen storage is one of the most critical steps in hydrogen economy. The media where hydrogen molecule is stored is important not only because of safety but also to generate maximum energy and consume minimum energy during the adsorption-desorption process. Porous coordination polymers have been considered as convenient hydrogen sorbents among other hydrogen storage systems due to their structural properties. Research in this field focused also on porous Prussian Blue Analogues incorporating [Fe(CN)6] 3- and [Fe(CN)5NO]3- building blocks due to their robustness at extreme conditions (e.g. high temperature and high pressure), easy preparation, and versatilities. The project discussed herein focuses on the preparation of five new Prussian Blue analogues incorporating [Fe(CN)5NH3] 3- and [Fe(CN)5pyrazine]3- building blocks. It is aimed to improve the porosity and increase the number of polar functional groups on the pore surfaces by substituting one of the cyanide groups with nitrogen donor ammonia or pyrazine group. M3[Fe(CN)5NH3]2 and M3[Fe(CN)5pz]2 type of Prussian Blue analogues with M= Cu2+, Ni2+, Co2+ were prepared and characterized by FTTR, XRD and TGA techniques. The effects of the ligands bound to central cation(Fe2+) and the type of the outer cation in the framework on the CN- stretching mode in IR spectrum have been studied. Cu3[Fe(CN)5NH3]2 , Ni3[Fe(CN)5NH3]2,and Co3[Fe(CN)5NH3]2 compounds have been shown to adopt Fm3mtype structure similar to classic Prussian Blue analogues. Cu3[Fe(CN)5pz]2 compound has exhibited four diffraction angles which belong to Fm3m space group and two additional peaks when Ni3[Fe(CN)5pz]2 has exhibited relatively weak diffraction pattern belonging to Fm3m space group. Thermal stabilities have been discussed and framework changes were observed with increasing temperature. TGA, IR, and XRD techniques have been performed to investigate the structural changes in target materials at different degassing temperatures. The adsorption profiles of nitrogen and hydrogen have been investigated at two different temperatures based on TGA results. Surface areas and hydrogen uptake capacities of five new Prussian Blue analogues have been studied. Co3[Fe(CN)5NH3]2 showed the highest surface area(243.2 m2 /g) while Ni3[Fe(CN)5NH3]2 showed the highest hydrogen uptake capacity(1.79 wt % H2) at 95°C among the studied materials. Cu3[Fe(CN)5pz]2 and Ni3[Fe(CN)5pz]2 compounds were observed to exhibit no hydrogen uptake. It is also observed that surface areas of Co3[Fe(CN)5NH3]2 and Ni3[Fe(CN)5NH3]2 compounds increased, surface areas of other three compounds decreased when they are degassed at 225°C. Hydrogen storage capacity is also increased from 1.07 wt % to 1.85 wt % significantly for Co3[Fe(CN)5NH3]2 by increasing the degassing temperature.