Browsing by Subject "Electrospinning techniques"

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    Encapsulation of active agents in electrospun nanofibers/nanowebs
    (The Fiber Society, 2013) Kayaci, Fatma; Aytac, Zeynep; Celebioglu, Asli; Uyar, Tamer
    In this study, we produce functional nanofibers/nanowebs containing active agents such as essential oils, antibacterials, antioxidants, flavors/fragrances via electrospinning technique. The encapsulation of these active agents into electrospun nanofibers/nanowebs was quite possible, however, their stability and/or shelf-life was limited due to their volatile nature. Nevertheless, by forming cyclodextrin inclusion complexes (CD-IC) with these active agents and incorporating CD-IC into electrospun nanofibers/nanowebs, we achieved high temperature stability, slow release and prolonged shelf-life for these active agents. These functional electrospun nanofibers/nanowebs containing active agents can be quite applicable in active food packaging, textiles, biotechnology, etc.
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    Encapsulation of vanillin/cyclodextrin inclusion complex in electrospun polyvinyl alcohol (PVA) nanowebs: prolonged shelf-life and high temperature stability of vanillin
    (2012-08) Kayaci, F.; Uyar, Tamer
    We produced functional nanowebs, containing vanillin, having prolonged shelf-life and high temperature stability facilitated by cyclodextrin (CD) inclusion complexation. Polyvinyl alcohol (PVA) nanowebs incorporating vanillin/cyclodextrin inclusion complex (vanillin/CD-IC) were produced via electrospinning technique. The vanillin/CD-IC was prepared with three types of CDs; α-CD, β-CD and γ-CD to find out the most favourable CD type for the stabilization of vanillin. PVA/vanillin/CD-IC nanofibres, having fibre diameters around ∼200 nm, were successfully electrospun from aqueous mixture of PVA and vanillin/CD-IC. Our results indicated that vanillin with enhanced durability and high temperature stability was achieved for PVA/vanillin/CD-IC nanowebs due to complexation of vanillin with CD, whereas the PVA nanofibres without CD-IC could not effectively preserve the vanillin. Additionally, we observed that PVA/vanillin/γ-CD-IC nanoweb was more effective for the stabilization and slow release of vanillin suggesting that the strength of interaction between vanillin and the γ-CD cavity is stronger when compared to α-CD and β-CD. © 2012 Elsevier Ltd. All rights reserved.
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    Highly fluorescent pyrene-functional polystyrene copolymer nanofibers for enhanced sensing performance of TNT
    (American Chemical Society, 2015) Senthamizhan, A.; Celebioglu A.; Bayir, S.; Gorur, M.; Doganci, E.; Yilmaz, F.; Uyar, Tamer
    A pyrene-functional polystyrene copolymer was prepared via 1,3-dipolar cycloaddition reaction (Sharpless-type click recation) between azide-functional styrene copolymer and 1-ethynylpyrene. Subsequently, nanofibers of pyrene-functional polystyrene copolymer were obtained by using electrospinning technique. The nanofibers thus obtained, found to preserve their parent fluorescence nature, confirmed the avoidance of aggregation during fiber formation. The trace detection of trinitrotoluene (TNT) in water with a detection limit of 5 nM was demonstrated, which is much lower than the maximum allowable limit set by the U.S. Environmental Protection Agency. Interestingly, the sensing performance was found to be selective toward TNT in water, even in the presence of higher concentrations of toxic metal pollutants such as Cd2+, Co2+, Cu2+, and Hg2+. The enhanced sensing performance was found to be due to the enlarged contact area and intrinsic nanoporous fiber morphology. Effortlessly, the visual colorimetric sensing performance can be seen by naked eye with a color change in a response time of few seconds. Furthermore, vapor-phase detection of TNT was studied, and the results are discussed herein. In terms of practical application, electrospun nanofibrous web of pyrene-functional polystyrene copolymer has various salient features including flexibility, reproducibility, and ease of use, and visual outputs increase their value and add to their advantage.
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    Microalgae immobilized by nanofibrous web for removal of reactive dyes from wastewater
    (American Chemical Society, 2015) Keskin, N. O. S.; Celebioglu A.; Uyar, Tamer; Tekinay, T.
    In this study, we have developed microalgae immobilized by polysulfone nanofibrous web (microalgae/PSU-NFW) for the removal of reactive dyes (Remazol Black 5 (RB5) and Reactive Blue 221 (RB221). Here, an electrospinning technique was used to produce polysulfone nanofibrous web (PSU-NFW) as a free-standing material on which microalgae Chlamydomona reinhardtii was immobilized on PSU-NFW. The decolorization capacities of microalgae/PSU-NFW were significantly higher than that of pristine PSU-NFW. The decolorization rate for RB5 was calculated as 72.97 ± 0.3% for microalgae/PSU-NFW, whereas it was 12.36 ± 0.3% for the pristine PSU-NFW. In the case of RB221 solution, decolorization rates were achieved as 30.2 ± 0.23 and 5.51 ± 0.4% for microalgae/PSU-NFW and pristine PSU-NFW, respectively. Reusability tests revealed that microalgae/PSU-NFW can be used in at least three successive decolorization steps in which the decolorization rate of the RB5 was found to be 51 ± 0.69% after the third reuse step. These results are promising and therefore suggest that microalgae/PSU-NFW could be applicable for the decolorization of dyes because of their versatility and reusability.
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    Polymer-free nanofibers from vanillin/cyclodextrin inclusion complexes: high thermal stability, enhanced solubility and antioxidant property
    (Royal Society of Chemistry, 2016) Celebioglu A.; Kayaci-Senirmak, F.; Ipek, S.; Durgun, Engin; Uyar, Tamer
    Vanillin/cyclodextrin inclusion complex nanofibers (vanillin/CD-IC NFs) were successfully obtained from three modified CD types (HPβCD, HPγCD and MβCD) in three different solvent systems (water, DMF and DMAc) via an electrospinning technique without using a carrier polymeric matrix. Vanillin/CD-IC NFs with uniform and bead-free fiber morphology were successfully produced and their free-standing nanofibrous webs were obtained. The polymer-free CD/vanillin-IC-NFs allow us to accomplish a much higher vanillin loading (∼12%, w/w) when compared to electrospun polymeric nanofibers containing CD/vanillin-IC (∼5%, w/w). Vanillin has a volatile nature yet, after electrospinning, a significant amount of vanillin was preserved due to complex formation depending on the CD types. Maximum preservation of vanillin was observed for vanillin/MβCD-IC NFs which is up to ∼85% w/w, besides, a considerable amount of vanillin (∼75% w/w) was also preserved for vanillin/HPβCD-IC NFs and vanillin/HPγCD-IC NFs. Phase solubility studies suggested a 1:1 molar complexation tendency between guest vanillin and host CD molecules. Molecular modelling studies and experimental findings revealed that vanillin:CD complexation was strongest for MβCD when compared to HPβCD and HPγCD in vanillin/CD-IC NFs. For vanillin/CD-IC NFs, water solubility and the antioxidant property of vanillin was improved significantly owing to inclusion complexation. In brief, polymer-free vanillin/CD-IC NFs are capable of incorporating a much higher loading of vanillin and effectively preserve volatile vanillin. Hence, encapsulation of volatile active agents such as flavor, fragrance and essential oils in electrospun polymer-free CD-IC NFs may have potential for food related applications by integrating the particularly large surface area of NFs with the non-toxic nature of CD and inclusion complexation benefits, such as high temperature stability, improved water solubility and an enhanced antioxidant property, etc.
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    Systematic hydrolysis of PIM-1 and electrospinning of hydrolyzed PIM-1 ultrafine fibers for an efficient removal of dye from water
    (Elsevier, 2017-12) Satilmis, B.; Budd, P. M.; Uyar, Tamer
    In this study, the Polymer of Intrinsic Microporosity (PIM-1) was systematically hydrolyzed in the presence of sodium hydroxide by varying the concentration of base, washing procedure and the time of the reaction. The chemical structure analyses confirmed that PIM-1 could be hydrolyzed by 65% up to 99% conversion depending on the synthesis procedure. The hydrolyzed PIM-1 samples have shown improved solubility which facilitates the fabrication of hydrolyzed PIM-1 ultrafine fibers by electrospinning technique. Extensive optimization studies were performed for the electrospinning of uniform and bead-free fibers from hydrolyzed PIM-1 with different degree of hydrolysis (65%, 86%, 94% and 99%). The electrospun hydrolysed PIM-1 fibrous samples have average fiber diameters (AFD) ranging from 0.58 ± 0.15 μm to 1.21 ± 0.15 μm, depending on the polymer concentration and applied electrospinning parameters. After electrospinning, self-standing hydrolyzed PIM-1 fibrous membranes were obtained which is useful as a filtering material for the adsorption of organic dyes from wastewater. Here, the capability of hydrolyzed PIM-1 electrospun fibrous membranes for the removal of dyes from aqueous solutions was investigated by using a batch adsorption process. The maximum adsorption capacity of fully hydrolyzed PIM-1 fibers was found 157 ± 16 mg g− 1 for Methylene Blue and 4 mg g− 1 for Congo red when the adsorption was conducted by 20 mg L− 1 dye solution without using any dilution. Moreover, maximum dye adsorption was also studied by using concentrated Methylene Blue solutions showing up to 272 mg g− 1 adsorption maximum. In addition, the self-standing fibrous hydrolyzed PIM-1 membrane was employed to separate Methylene Blue from an aqueous system by filtration without the necessity of additional driving force. The results indicate that hydrolyzed PIM-1 electrospun nanofibrous membranes can be a promising filtering material for wastewater treatment