TY - JOUR AB - In the context of the energy transition to renewables, the spotlight is on large systems connected to the power grid, but this also offers room for smaller, more specialized applications. Photovoltaics, in particular, offer the possibility of the self-sufficient supply of smaller electrical appliances on smaller scales. The idea of making previously unused surfaces usable is by no means new, and textiles such as backpacks, tent tarpaulins and other covers are particularly suitable for this purpose. In order to create a non-toxic and easily recyclable product, dye-sensitized solar cells (DSSC), which can be manufactured through electrospinning with a textile feel, are an attractive option here. Therefore, this paper investigates a needle electrospun nanofiber mat, whose spin solution contains polyacrylonitrile (PAN) dissolved in dimethyl sulfoxide (DMSO) as well es TiO2 nanoparticles. In addition to characterization, the nanofiber mat was dyed in a solution containing anthocyanins to later serve as a front electrode for a dye-sensitized solar cell. Although of lower efficiency, the DSSC provides stable results over two months of measurement. AU - Dotter, Marius AU - Placke, Lion Lukas AU - Storck, Jan Lukas AU - Güth, Uwe ID - 2577 IS - 4 JF - Tekstilec KW - dye-sensitized solar cells (DSSC) KW - long-term stability KW - electrospinning KW - polyacrylonitrile (PAN) KW - TiO2 nanoparticles SN - 0351-3386 TI - Characterization of PAN-TiO2 Nanofiber Mats and their Application as Front Electrodes for Dye-sensitized Solar Cells VL - 65 ER - TY - JOUR AB - Polyacrylonitrile (PAN) nanofiber mats are typical precursors for carbon nanofibers. They can be fixed or even elongated during stabilization and subsequent carbonization to gain straight, mechanically robust carbon nanofibers. These processes necessitate additional equipment or are—if the nanofiber mats are just fixed at the edges—prone to resulting in the specimens breaking, due to an uneven force distribution. Hence, we showed in a previous study that electrospinning PAN on aluminum foils and stabilizing them fixed on these substrates, is a suitable solution to keep the desired morphology after stabilization and incipient carbonization. Here, we report on the influence of different metallic and semiconductor substrates on the physical and chemical properties of the nanofiber mats after stabilization and carbonization at temperatures up to 1200 °C. For stabilization on a metal substrate, an optimum stabilization temperature of slightly above 240 °C was found, approached with a heating rate of 0.25 K/min. Independent from the substrate material, SEM images revealed less defect fibers in the nanofiber mats stabilized and incipiently carbonized on a metal foil. Finally, high-temperature carbonization on different substrates is shown to allow for producing metal/carbon nano-composites. AU - Storck, Jan Lukas AU - Brockhagen, Bennet AU - Grothe, Timo AU - Sabantina, Lilia AU - Kaltschmidt, Bernhard AU - Tuvshinbayar, Khorolsuren AU - Braun, Laura AU - Tanzli, Ewin AU - Hütten, Andreas AU - Ehrmann, Andrea ID - 1081 IS - 1 JF - C KW - polyacrylonitrile (PAN) KW - nanofibers KW - electrospinning KW - aluminum KW - copper KW - tin KW - titanium KW - silicon wafer KW - steel KW - stabilization and carbonization TI - Stabilization and Carbonization of PAN Nanofiber Mats Electrospun on Metal Substrates VL - 7 ER - TY - JOUR AB - Electrospinning can be used to prepare nanofibers from various polymers and polymer blends. The adhesion of nanofibers to the substrates on which they are electrospun varies greatly with the substrate material and structure. In some cases, good adhesion is desired to produce sandwich structures by electrospinning one material directly onto another. This is the case, e.g., with dye-sensitized solar cells (DSSCs). While both pure foil DSSCs and pure electrospun DSSCs have been examined, a combination of both technologies can be used to combine their advantages, e.g., the lateral strength of foils with the large surface-to-volume ratio of electrospun nanofibers. Here, we investigate the morphology and adhesion of electrospun nanofibers on different foil substrates containing materials commonly used in DSSCs, such as graphite, poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) or TiO2. The results show that the foil material strongly influences the adhesion, while a plasma pretreatment of the foils showed no significant effect. Moreover, it is well known that conductive substrates can alter the morphology of nanofiber mats, both at microscopic and macroscopic levels. However, these effects could not be observed in the current study. AU - Hellert, Christian AU - Wortmann, Martin AU - Frese, Natalie AU - Grötsch, Georg AU - Cornelißen, Carsten AU - Ehrmann, Andrea ID - 1617 IS - 2 JF - Coatings KW - electrospinning KW - polyacrylonitrile (PAN) KW - nanofibers KW - conductive foils KW - adhesion KW - dye-sensitized solar cells (DSSCs) KW - fiber orientation TI - Adhesion of Electrospun Poly(acrylonitrile) Nanofibers on Conductive and Isolating Foil Substrates VL - 11 ER - TY - JOUR AB - Polyacrylonitrile (PAN) nanofibers, prepared by electrospinning, are often used as a precursor for carbon nanofibers. The thermal carbonization process necessitates a preceding oxidative stabilization, which is usually performed thermally, i.e., by carefully heating the electrospun nanofibers in an oven. One of the typical problems occurring during this process is a strong deformation of the fiber morphologies—the fibers become thicker and shorter, and show partly undesired conglutinations. This problem can be solved by stretching the nanofiber mat during thermal treatment, which, on the other hand, can lead to breakage of the nanofiber mat. In a previous study, we have shown that the electrospinning of PAN on aluminum foils and the subsequent stabilization of this substrate is a simple method for retaining the fiber morphology without breaking the nanofiber mat. Here, we report on the impact of different aluminum foils on the physical and chemical properties of stabilized PAN nanofibers mats, and on the following incipient carbonization process at a temperature of max. 600 °C, i.e., below the melting temperature of aluminum. AU - Storck, Jan Lukas AU - Grothe, Timo AU - Tuvshinbayar, Khorolsuren AU - Diestelhorst, Elise AU - Wehlage, Daria AU - Brockhagen, Bennet AU - Wortmann, Martin AU - Frese, Natalie AU - Ehrmann, Andrea ID - 670 IS - 9 JF - Fibers KW - polyacrylonitrile (PAN) KW - nanofibers KW - electrospinning KW - stabilization KW - carbonization SN - 2079-6439 TI - Stabilization and Incipient Carbonization of Electrospun Polyacrylonitrile Nanofibers Fixated on Aluminum Substrates VL - 8 ER - TY - JOUR AB - Polyacrylonitrile (PAN) belongs to the group of polymers that are often used for electrospinning, as it can be applied as a pre-cursor for carbon nanofibers and is spinnable from the low-toxic solvent dimethyl sulfoxide (DMSO). While the influence of different spinning parameters on fibre morphology and mass per unit area was investigated in a previous study, here we report on the impact of the spinning solution, using DMSO as a solvent and wire-based (needleless) electrospinning. Our results show that a broad range of solid contents can be applied, providing the opportunity to tailor the fibre diameter distribution or to optimize the areal weight of the nanofibrous mat by changing this parameter, while the chemical composition of the fibres remains identical. AU - Grothe, Timo AU - Storck, Jan Lukas AU - Dotter, Marius AU - Ehrmann, Andrea ID - 680 IS - 3 JF - Tekstilec KW - needleless electrospinning KW - polyacrylonitrile (PAN) KW - nanofibrous mat KW - dimethyl sulfoxide (DMSO) KW - Fourier-transform infrared (FTIR) spectroscopy TI - Impact of solid content in the electrospinning solution on the physical and chemical properties of polyacrylonitrile (PAN) nanofibrous mats VL - 63 ER - TY - JOUR AB - Electrospun polyacrylonitrile (PAN) nanofi brous mats belong to typical precursor materials of carbon nanofibres. They have, however, the problem that they need to be fixed or even stretched during stabilisation and ideally also during carbonisation in order to avoid undesired conglutinations and deformations of the original nanofibre morphology, resulting in brittle behaviour of the macroscopic nanofibrous mat, which impedes several applications. In an earlier investigation, blending PAN with ZnO was shown to increase fibre diameters and lead to unproblematic stabilisation and carbonisation of nanofibrous mats. ZnO, on the other hand, may have a negative impact on biotechnological applications such as tissue engineering. Here, we thus report on the morphological and chemical modifi cations due to blending PAN electrospinning solutions with different amounts of casein. By optimising the PAN : casein ratio, relatively thick, straight nanofibres are obtained, which can be stabilised and carbonised unambiguously, without the well-known negative impact on cell adhesion due to the addition of ZnO. AU - Diestelhorst, Elise AU - Mance, Fjoralba AU - Mamun, Al AU - Ehrmann, Andrea ID - 643 IS - 1 JF - TEKSTILEC KW - electrospinning KW - polyacrylonitrile (PAN) KW - casein KW - nanofibrous mat KW - stabilisation KW - carbonisation KW - tissue engineering SN - 0351-3386 TI - Chemical and Morphological Modification of PAN Nanofibrous Mats with Addition of Casein after VL - 63 ER - TY - JOUR AB - The image processing of pictures from fibres and fibrous materials facilitates the investigation of diverse geometrical properties, such as yarn hairiness, fibre bifurcations or fibre lengths and diameters. Such irregular sample sets are naturally suitable to the statistical examination of images, using a random-walk algorithm. This results in the calculation of the so-called Hurst exponent, which is the asymptotic scaling exponent of the mean squared displacement of the walker’s position. Previous investigations have proven the appropriateness of this method for examinations of diff erent fibres, yarns and textile fabrics. In a recent study, we used AFM (atomic force microscopy) images, split into different greyscales, to analyse and quantify differences between various nanofibre mats created from polyacrylonitrile. In addition to the strong influence of the nanofibre diameters, a certain impact of the AFM settings was also seen and must be taken into account in future research. AU - Blachowicz, Tomasz AU - Böhm, Tobias AU - Grzybowski, Jacek AU - Domino, Krzysztof AU - Ehrmann, Andrea ID - 660 IS - 2 JF - TEKSTILEC KW - electrospinning KW - polyacrylonitrile (PAN) KW - nanofibrous mat KW - atomic force microscopy (AFM) KW - Hurst exponent KW - random walk SN - 0351-3386 TI - Evaluation of Mechanical and Physical Characteristics of Eco blended Melange Yarns VL - 63 ER - TY - JOUR AB - The field of carbon nanofibers has been growing in terms of technological development and seeking attention because of their dominant chemical properties, mechanical strength, and electrical conductivity. Catalytic and electrospinning techniques are currently the conventional methods for fabrication of carbon nanofibers in a two-step process that includes stabilization and carbonization of polyacrylonitrile (PAN) nanofibers, respectively. Recently, the industrial and medical sectors dealing with nanofibrous materials are not having ample options but to accept the use of already approved materials which are quite expensive and lack the flexibility in manipulating their surface and chemical properties for specific applications. To overcome these limitations, carbon nanofibers are being validated for their multifunctional role in various forms. This article reviews the recent advancements in the fabrication of carbon nanofibers and additionally pointing out their significance for applications in the industrial and biomedical sector for their potential role in the future. In this article, we explicitly focus on the recent breakthroughs in the field of carbon nanofibers, especially in the area of their commercial applications. Our goal is to depict ways for enhancing the chemical and structural properties of these nanofibers and providing beneficiary, low-cost alternatives to the currently available materials in the medical field as well as the industrial area. AU - Yadav, Daman AU - Amini, Fedi AU - Ehrmann, Andrea ID - 672 JF - European Polymer Journal KW - Carbon nanofibers KW - Vapor grown carbon nanofibers KW - Chemical vapor deposition KW - Polyacrylonitrile KW - Dimethylformamide SN - 0014-3057 TI - Recent advances in carbon nanofibers and their applications – A review VL - 138 ER - TY - JOUR AB - Nanofi brous mats can be used as a substrate for eukaryotic cell growth in biotechnology, tissue engineering, etc. Several adherent cells (e.g. human fibroblasts) have been shown to grow well on fine fibres. For most applications, it is necessary to sterilize nanofibrous mats before adding the cells. Another possibility would be the addition of antibiotics and antimycotics to the cell culture medium to prevent microbial infection. However, antibiotics are disadvantageous since they might promote the growth of resistant bacteria in possible future medical applications of nanofibrous mats. Possible sterilization techniques include autoclaving, UV-sterilization, ozone treatment, heat sterilization and other techniques which usually necessitate more expensive equipment, such as gamma irradiation. Systematic examinations of the infl uence of different sterilization techniques on the cell growth on nanofibrous mats have not yet been reported in the literature. Here, we report on the first experimental investigations of the effect of sterilization with different methods on the properties of polyacrylonitrile (PAN)/gelatine nanofibrous mats, and the resulting growth and adhesion of Chinese hamster ovary cells. While all techniques under investigation yielded sterile nanofibrous mats, autoclaving and heat sterilization change the PAN/gelatine fibre morphology. Ozone, on the other hand, modifies the pH value of the culture medium and partly impedes cell adhesion. UV sterilization also suggests a chemical modification of the nanofibrous mat. Unexpectedly, heat sterilization resulted in the highest amount of adherent Chinese hamster ovary cells grown on PAN/gelatine nanofibrous mats in spite of gelatine melting. AU - Wehlage, Daria AU - Blattner, Hannah AU - Sabantina, Lilia AU - Böttjer, Robin AU - Grothe, Timo AU - Rattenholl, Anke AU - Gudermann, Frank AU - Lütkemeyer, Dirk AU - Ehrmann, Andrea ID - 166 IS - 2 JF - Tekstilec KW - polyacrylonitrile/gelatine nanofibrous mats KW - sterilization KW - autoclaving KW - ozone KW - UV sterilization KW - heat sterilization KW - cell growth KW - adherent cells KW - CHO cells KW - tissue engineering TI - Sterilization of PAN/Gelatin Nanofibrous Mats for Cell Growth VL - 62 ER - TY - JOUR AB - Polyacrylonitrile belongs to the most often used precursors for carbon fibers. Using electrospinning, polyacrylonitrile nanofiber mats can be prepared and afterwards stabilized and carbonized to prepare carbon nanofiber mats which, by adding other materials, will be useful for several applications. One of these materials is TiO2, which has photocatalytic properties and can thus be used as a photocatalyst for photodegradation of dyes. Here, we report on a detailed study of electrospinning, stabilization, and carbonization of electrospun polyacrylonitrile/TiO2 mats with varying TiO2 content. Depending on the amount of TiO2 in the nanofibers, the fiber morphology changes strongly, indicating an upper limit for the preparation of carbon/TiO2 nanofibers with smooth surface, but offering an even increased inner surface of the rougher carbon/TiO2 nanofibers with increased TiO2 content due to better maintenance of the fibrous structure during stabilization. AU - Sabantina, Lilia AU - Böttjer, Robin AU - Wehlage, Daria AU - Grothe, Timo AU - Klöcker, Michaela AU - García-Mateos, Francisco José AU - Rodríguez-Mirasol, José AU - Cordero, Tomás AU - Ehrmann, Andrea ID - 573 JF - Journal of Engineered Fibers and Fabrics KW - Polyacrylonitrile KW - PAN KW - TiO2 KW - nanofiber mat KW - electrospinning KW - composite KW - stabilization KW - carbonization TI - Morphological study of stabilization and carbonization of polyacrylonitrile/TiO2 nanofiber mats VL - 14 ER - TY - JOUR AB - Electrospinning can be used to produce nanofiber mats. One of the often used polymers for electrospinning is polyacrylonitrile (PAN), especially for the production of carbon nanofibers, but also for a diverse number of other applications. For some of these applications—e.g., creation of nano-filters—the dimensional stability of the nanofiber mats is crucial. While relaxation processes—especially dry, wet and washing relaxation—are well-known and often investigated for knitted fabrics, the dimensional stability of nanofiber mats has not yet been investigated. Here we report on the wet relaxation of PAN nanofiber mats, which are dependent on spinning and solution parameters such as: voltage, electrode distance, nanofiber mat thickness, and solid content in the solution. Our results show that wet relaxation has a significant effect on the samples, resulting in a dimensional change that has to be taken into account for nanofiber mats in wet applications. While the first and second soaking in pure water resulted in an increase of the nanofiber mat area up to approximately 5%, the dried sample, after the second soaking, conversely showed an area reduced by a maximum of 5%. For soaking in soap water, small areal decreases between approximately 1–4% were measured. AU - Grothe, Timo AU - Sabantina, Lilia AU - Klöcker, Michaela AU - Juhász Junger, Irén AU - Döpke, Christoph AU - Ehrmann, Andrea ID - 522 IS - 1 JF - Technologies KW - electrospinning KW - filter KW - wet relaxation KW - dimensions KW - polyacrylonitrile (PAN) TI - Wet relaxation of electrospun nanofiber mats VL - 7 ER - TY - JOUR AB - TiO2 is a semiconductor that is commonly used in dye-sensitized solar cells (DSSCs). However, the necessity of sintering the TiO2 layer is usually problematic due to the desired temperatures of typically 500 °C in cells that are prepared on polymeric or textile electrodes. This is why textile-based DSSCs often use metal fibers or metallic woven fabrics as front electrodes on which the TiO2 is coated. Alternatively, several research groups investigate the possibilities to reduce the necessary sintering temperatures by chemical or other pre-treatments of the TiO2. Here, we report on a simple method to avoid the sintering step by using a nanofiber mat as a matrix embedding TiO2 nanoparticles. The TiO2 layer can be dyed with natural dyes, resulting in a similar bathochromic shift of the UV/Vis spectrum, as it is known from sintered TiO2 on glass substrates, which indicates an equivalent chemical bonding. Our results indicate a new possibility for producing textile-based DSSCs with TiO2, even on textile fabrics that are not high-temperature resistant. AU - Ehrmann, Andrea AU - Mamun, Al AU - Trabelsi, Marah AU - Klöcker, Michaela AU - Sabantina, Lilia AU - Großerhode, Christina AU - Blachowicz, Tomasz AU - Grötsch, Georg AU - Cornelißen, Carsten AU - Streitenberger, Almuth ID - 570 IS - 7 JF - Fibers KW - TiO2 KW - dye-sensitized solar cell (DSSC) KW - textile-based DSSC KW - electrospinning KW - nanofiber mat KW - polyacrylonitrile (PAN) TI - Electrospun nanofiber mats with embedded non-sintered TiO2 for dye-sensitized solar cells (DSSCs) VL - 7 ER -