@article{2577, abstract = { 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. }, author = {Dotter, Marius and Placke, Lion Lukas and Storck, Jan Lukas and Güth, Uwe}, issn = {2350-3696}, journal = {Tekstilec}, keywords = {dye-sensitized solar cells (DSSC), long-term stability, electrospinning, polyacrylonitrile (PAN), TiO2 nanoparticles}, number = {4}, pages = {298--306}, publisher = {University of Ljubljana}, title = {{Characterization of PAN-TiO2 Nanofiber Mats and their Application as Front Electrodes for Dye-sensitized Solar Cells}}, doi = {10.14502/tekstilec.65.2022081}, volume = {65}, year = {2023}, } @article{2019, abstract = { Electrospinning is often investigated for biotechnological applications, such as tissue engineering and cell growth in general. In many cases, three-dimensional scaffolds would be advantageous to prepare tissues in a desired shape. Some studies thus investigated 3D-printed scaffolds decorated with electrospun nanofibers. Here, we report on the influence of 3D-printed substrates on fiber orientation and diameter of a nanofiber mat, directly electrospun on conductive and isolating 3D-printed objects, and show the effect of shadowing, taking 3D-printed ears with electrospun nanofiber mats as an example for potential and direct application in tissue engineering in general. }, author = {Bauer, Laura and Brandstäter, Lisa and Letmate, Mika and Palachandran, Manasi and Wadehn, Fynn Ole and Wolfschmidt, Carlotta and Grothe, Timo and Güth, Uwe and Ehrmann, Andrea}, issn = {2227-7080}, journal = {Technologies}, keywords = {needleless electrospinning, poly(lactic acid) (PLA), poly(acrylonitrile) (PAN), nanospider, cell adhesion, cell proliferation, 3D printing}, number = {3}, publisher = {MDPI AG}, title = {{Electrospinning for the Modification of 3D Objects for the Potential Use in Tissue Engineering}}, doi = {10.3390/technologies10030066}, volume = {10}, year = {2022}, } @article{1081, abstract = { 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. }, author = {Storck, Jan Lukas and Brockhagen, Bennet and Grothe, Timo and Sabantina, Lilia and Kaltschmidt, Bernhard and Tuvshinbayar, Khorolsuren and Braun, Laura and Tanzli, Ewin and Hütten, Andreas and Ehrmann, Andrea}, issn = {2311-5629}, journal = {C}, keywords = {polyacrylonitrile (PAN), nanofibers, electrospinning, aluminum, copper, tin, titanium, silicon wafer, steel, stabilization and carbonization}, number = {1}, publisher = {MDPI AG}, title = {{Stabilization and Carbonization of PAN Nanofiber Mats Electrospun on Metal Substrates}}, doi = {10.3390/c7010012}, volume = {7}, year = {2021}, } @article{1615, abstract = { Two-dimensional structures, either periodic or random, can be classified by diverse mathematical methods. Quantitative descriptions of such surfaces, however, are scarce since bijective definitions must be found to measure unique dependency between described structures and the chosen quantitative parameters. To solve this problem, we use statistical analysis of periodic fibrous structures by Hurst exponent distributions. Although such a Hurst exponent approach was suggested some years ago, the quantitative analysis of atomic force microscopy (AFM) images of nanofiber mats in such a way was described only recently. In this paper, we discuss the influence of typical AFM image post-processing steps on the gray-scale-resolved Hurst exponent distribution. Examples of these steps are polynomial background subtraction, aligning rows, deleting horizontal errors and sharpening. Our results show that while characteristic features of these false-color images may be shifted in terms of gray-channel and Hurst exponent, they can still be used to identify AFM images and, in the next step, to quantitatively describe AFM images of nanofibrous surfaces. Such a gray-channel approach can be regarded as a simple way to include some information about the 3D structure of the image. }, author = {Blachowicz, Tomasz and Domino, Krzysztof and Koruszowic, Michał and Grzybowski, Jacek and Böhm, Tobias and Ehrmann, Andrea}, issn = {2076-3417}, journal = {Applied Sciences}, keywords = {Hurst exponent distribution, random walk, atomic force microscopy (AFM), electrospinning, poly(acrylonitrile) (PAN)}, number = {5}, publisher = {MDPI AG}, title = {{Statistical Analysis of Nanofiber Mat AFM Images by Gray-Scale-Resolved Hurst Exponent Distributions}}, doi = {10.3390/app11052436}, volume = {11}, year = {2021}, } @article{1617, abstract = { 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.}, author = {Hellert, Christian and Wortmann, Martin and Frese, Natalie and Grötsch, Georg and Cornelißen, Carsten and Ehrmann, Andrea}, issn = {2079-6412}, journal = {Coatings}, keywords = {electrospinning, polyacrylonitrile (PAN), nanofibers, conductive foils, adhesion, dye-sensitized solar cells (DSSCs), fiber orientation}, number = {2}, publisher = {MDPI AG}, title = {{Adhesion of Electrospun Poly(acrylonitrile) Nanofibers on Conductive and Isolating Foil Substrates}}, doi = {10.3390/coatings11020249}, volume = {11}, year = {2021}, } @article{670, abstract = {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.}, author = {Storck, Jan Lukas and Grothe, Timo and Tuvshinbayar, Khorolsuren and Diestelhorst, Elise and Wehlage, Daria and Brockhagen, Bennet and Wortmann, Martin and Frese, Natalie and Ehrmann, Andrea}, issn = {2079-6439}, journal = {Fibers}, keywords = {polyacrylonitrile (PAN), nanofibers, electrospinning, stabilization, carbonization}, number = {9}, title = {{Stabilization and Incipient Carbonization of Electrospun Polyacrylonitrile Nanofibers Fixated on Aluminum Substrates}}, doi = {10.3390/fib8090055}, volume = {8}, year = {2020}, } @article{680, abstract = {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.}, author = {Grothe, Timo and Storck, Jan Lukas and Dotter, Marius and Ehrmann, Andrea}, journal = {Tekstilec}, keywords = {needleless electrospinning, polyacrylonitrile (PAN), nanofibrous mat, dimethyl sulfoxide (DMSO), Fourier-transform infrared (FTIR) spectroscopy}, number = {3}, pages = {225--232}, title = {{Impact of solid content in the electrospinning solution on the physical and chemical properties of polyacrylonitrile (PAN) nanofibrous mats}}, doi = {10.14502/Tekstilec2020.63.225-232}, volume = {63}, year = {2020}, } @article{643, abstract = {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.}, author = {Diestelhorst, Elise and Mance, Fjoralba and Mamun, Al and Ehrmann, Andrea}, issn = {0351-3386}, journal = {TEKSTILEC}, keywords = {electrospinning, polyacrylonitrile (PAN), casein, nanofibrous mat, stabilisation, carbonisation, tissue engineering}, number = {1}, pages = {38--49}, title = {{Chemical and Morphological Modification of PAN Nanofibrous Mats with Addition of Casein after}}, doi = {10.14502/tekstilec2020.63.38-49}, volume = {63}, year = {2020}, } @article{660, abstract = {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.}, author = {Blachowicz, Tomasz and Böhm, Tobias and Grzybowski, Jacek and Domino, Krzysztof and Ehrmann, Andrea}, issn = {0351-3386}, journal = {TEKSTILEC}, keywords = {electrospinning, polyacrylonitrile (PAN), nanofibrous mat, atomic force microscopy (AFM), Hurst exponent, random walk}, number = {2}, pages = {94--103}, title = {{Evaluation of Mechanical and Physical Characteristics of Eco blended Melange Yarns}}, doi = {10.14502/tekstilec2020.63.94-103}, volume = {63}, year = {2020}, } @article{664, abstract = {Thermally stabilized and subsequently carbonized nanofibers are a promising material for many technical applications in fields such as tissue engineering or energy storage. They can be obtained from a variety of different polymer precursors via electrospinning. While some methods have been tested for post-carbonization doping of nanofibers with the desired ingredients, very little is known about carbonization of blend nanofibers from two or more polymeric precursors. In this paper, we report on the preparation, thermal treatment and resulting properties of poly(acrylonitrile) (PAN)/poly(vinylidene fluoride) (PVDF) blend nanofibers produced by wire-based electrospinning of binary polymer solutions. Using a wide variety of spectroscopic, microscopic and thermal characterization methods, the chemical and morphological transition during oxidative stabilization (280 °C) and incipient carbonization (500 °C) was thoroughly investigated. Both PAN and PVDF precursor polymers were detected and analyzed qualitatively and quantitatively during all stages of thermal treatment. Compared to pure PAN nanofibers, the blend nanofibers showed increased fiber diameters, strong reduction of undesired morphological changes during oxidative stabilization and increased conductivity after carbonization.}, author = {Wortmann, Martin and Frese, Natalie and Mamun, Al and Trabelsi, Marah and Keil, Waldemar and Büker, Björn and Javed, Ali and Tiemann, Michael and Moritzer, Elmar and Ehrmann, Andrea and Hütten, Andreas and Schmidt, Claudia and Gölzhäuser, Armin and Hüsgen, Bruno and Sabantina, Lilia}, issn = {2079-4991}, journal = {Nanomaterials}, keywords = {electrospinning, carbon nanofiber, polymer blend, stabilization, carbonization, poly(acrylonitrile) (PAN), poly(vinylidene fluoride) (PVDF)}, number = {6}, title = {{Chemical and Morphological Transition of Poly(acrylonitrile)/Poly(vinylidene Fluoride) Blend Nanofibers during Oxidative Stabilization and Incipient Carbonization}}, doi = {10.3390/nano10061210}, volume = {10}, year = {2020}, } @article{573, abstract = {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.}, author = {Sabantina, Lilia and Böttjer, Robin and Wehlage, Daria and Grothe, Timo and Klöcker, Michaela and García-Mateos, Francisco José and Rodríguez-Mirasol, José and Cordero, Tomás and Ehrmann, Andrea}, journal = {Journal of Engineered Fibers and Fabrics}, keywords = {Polyacrylonitrile, PAN, TiO2, nanofiber mat, electrospinning, composite, stabilization, carbonization}, pages = {1--8}, title = {{ Morphological study of stabilization and carbonization of polyacrylonitrile/TiO2 nanofiber mats}}, doi = {10.1177/1558925019862242}, volume = {14}, year = {2019}, } @article{522, abstract = {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.}, author = {Grothe, Timo and Sabantina, Lilia and Klöcker, Michaela and Juhász Junger, Irén and Döpke, Christoph and Ehrmann, Andrea}, journal = {Technologies }, keywords = {electrospinning, filter, wet relaxation, dimensions, polyacrylonitrile (PAN)}, number = {1}, title = {{Wet relaxation of electrospun nanofiber mats}}, doi = {10.3390/technologies7010023}, volume = {7}, year = {2019}, } @article{570, abstract = {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. }, author = {Ehrmann, Andrea and Mamun, Al and Trabelsi, Marah and Klöcker, Michaela and Sabantina, Lilia and Großerhode, Christina and Blachowicz, Tomasz and Grötsch, Georg and Cornelißen, Carsten and Streitenberger, Almuth}, journal = {Fibers}, keywords = {TiO2, dye-sensitized solar cell (DSSC), textile-based DSSC, electrospinning, nanofiber mat, polyacrylonitrile (PAN)}, number = {7}, title = {{Electrospun nanofiber mats with embedded non-sintered TiO2 for dye-sensitized solar cells (DSSCs)}}, doi = {10.3390/fib7070060}, volume = {7}, year = {2019}, }