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 - 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.
AU - Bauer, Laura
AU - Brandstäter, Lisa
AU - Letmate, Mika
AU - Palachandran, Manasi
AU - Wadehn, Fynn Ole
AU - Wolfschmidt, Carlotta
AU - Grothe, Timo
AU - Güth, Uwe
AU - Ehrmann, Andrea
ID - 2019
IS - 3
JF - Technologies
KW - needleless electrospinning
KW - poly(lactic acid) (PLA)
KW - poly(acrylonitrile) (PAN)
KW - nanospider
KW - cell adhesion
KW - cell proliferation
KW - 3D printing
TI - Electrospinning for the Modification of 3D Objects for the Potential Use in Tissue Engineering
VL - 10
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 - 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.
AU - Blachowicz, Tomasz
AU - Domino, Krzysztof
AU - Koruszowic, Michał
AU - Grzybowski, Jacek
AU - Böhm, Tobias
AU - Ehrmann, Andrea
ID - 1615
IS - 5
JF - Applied Sciences
KW - Hurst exponent distribution
KW - random walk
KW - atomic force microscopy (AFM)
KW - electrospinning
KW - poly(acrylonitrile) (PAN)
TI - Statistical Analysis of Nanofiber Mat AFM Images by Gray-Scale-Resolved Hurst Exponent Distributions
VL - 11
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 - 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.
AU - Wortmann, Martin
AU - Frese, Natalie
AU - Mamun, Al
AU - Trabelsi, Marah
AU - Keil, Waldemar
AU - Büker, Björn
AU - Javed, Ali
AU - Tiemann, Michael
AU - Moritzer, Elmar
AU - Ehrmann, Andrea
AU - Hütten, Andreas
AU - Schmidt, Claudia
AU - Gölzhäuser, Armin
AU - Hüsgen, Bruno
AU - Sabantina, Lilia
ID - 664
IS - 6
JF - Nanomaterials
KW - electrospinning
KW - carbon nanofiber
KW - polymer blend
KW - stabilization
KW - carbonization
KW - poly(acrylonitrile) (PAN)
KW - poly(vinylidene fluoride) (PVDF)
SN - 2079-4991
TI - Chemical and Morphological Transition of Poly(acrylonitrile)/Poly(vinylidene Fluoride) Blend Nanofibers during Oxidative Stabilization and Incipient Carbonization
VL - 10
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 -