The mixture of polyaniline (PANi) and PANi grafted multi-walled carbon nanotube (PANi-g-MWNT) was prepared by two step reaction sequences. MWNT was first functionalized with 4-aminobenzoic acid via “direct” Firedel-Crafts acylation in polyphosphoric acid (PPA)/phosphorous pentoxide (P2O5) medium to afford aminobenzoyl-functionalized MWNT (AF-MWNT). Then, aniline was polymerized via in-situ static interfacial polymerization in H2O/CH2Cl2 in the presence of AF-MWNT in organic phase to yield the mixture of PANi and PANi-g-MWNT. The mixture was characterized with a various analytical techniques such as Fourier transform infrared spectroscopy (FT-IR), wide angle x-ray diffraction (WAXD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), cyclic voltammogram (CV). Even after dedoping, the mixture displayed semimetallic conductivity (4.9 S/cm). The capacitance of the mixture was also greatly enhanced and its capacitance decay with respect to cycle times was significantly reduced.

Electrospun polymer nanofiber materials have attracted tremendous interest in sensor applications as their effective sensing surface area dramatically increases with decreasing fiber diameter. The highly tunable polymer composite chemistry and surface functionality of the nanofiber material provides a wide platform for exploring different applications, such as filtration media, sound isolation materials, and sensor components. This paper presents a nanofiber sensor platform device composed of electrospun polymer/carbon composite nanofibers combined with electrodes directly printed onto the surface of the electrospun fiber mat. This structure forms an integrated sensor system for detecting various chemical vapors including volatile organic compounds (VOCs) and oxidative gases. In this sensor, the composite polymer nanofibers form a chemo-resistor sensing material, and the conductivity of these composite sensing materials varies with chemical vapor exposure. The sensor performance exhibits very stable baselines with dramatically reduced noise levels compared to conventional interdigitated electrodes. Furthermore, the sensor response to different vapors shows a linear relationship between conductivity change and vapor concentration in the range of ppb – ppm for some analytes, including methanol, chloroform and ozone. The sensitivity and selectivity of these sensors to different vapor analytes will also be discussed.

Electroactive conducting polymers are currently studied for use in smart textiles that incorporate sensing, actuation, control, and data transmission. The development of intelligent garments that integrate these various functionalities over wide areas (i.e. the human body) requires the production of long, highly conductive, and mechanically robust fibers. This study focuses on the electrical, mechanical and electrochemical characterization of high aspect ratio polypyrrole fibers produced using a novel, custom-built fiber slicing instrument. In order to ensure high conductivity and mechanical robustness, the fibers are sliced from tetra-ethylammonium hexafluorophosphate-doped polypyrrole thin films electrodeposited onto a glassy carbon crucible. The computer-controlled, four-axis slicing instrument precisely cuts the film into thin, long fibers by running a sharp blade over the crucible in a continuous helical pattern. This versatile fabrication process has been used to produce free-standing fibers with square cross-sections of 2 μm × 3 μm, 20 μm × 20 μm, and 100 μm × 20 μm with lengths of 15 mm, 460 mm, and 1,200 mm, respectively. An electrochemical dynamic mechanical analyzer built in-house for nano- and microfiber testing was used to perform stress-strain and conductivity measurements in air. The fibers were found to, on average, have an elastic modulus of 1.7 GPa, yield strength of 37 MPa, ultimate tensile strength of 80 MPa, elongation at break of 49%, and an electrical conductivity of 12,700 S/m. SEM micrographs show that the fibers are free of defects and have cleanly cut edges. Preliminary measurements of the fibers’ strain-resistance relationship have resulted in gage factors suitable for strain sensing applications. Initial tests of the actuation performance of fibers in neat 1-butyl-3-methylimidazolium hexaflourophosphate have shown promising results. These monofilament fibers may be spun into yarns or braided into 2- and 3-dimensional structures for use as actuators, sensors, antennae, and electrical interconnects in smart fabrics.

Photo active fibers containing dye anchored Nb2O5 nanorods, hole conduction and electron conduction materials were synthesized by the electrospinning technique. A 1.92 cm2 piece of fabric, composed of randomly aligned nanorods, was tested as a photovoltaic device under standard illumination conditions. The solar fabric exhibited an open circuit voltage (Voc) of ˜0.67 V, a short current density (JSC) of 4.77×10-4 mA/cm2, a fill factor (FF) of ˜15%, and an overall photovoltaic conversion efficiency (η) of 4.5×10-7%. This article presents for the first time the application of Nb2O5 in solar fabric.

In this paper, we report on the preparation and applications of nanofiber networks, particularly in the area of optelectronics. The major topics are (i) carbon nanotubes grown on carbon nanofibers for a field emitter, (ii) dye-sensitized ZnO nanowires grown on carbon nanofibers for a photoelectrochemical cell, (iii) nanofiber coatings for coloring, and (iv) nanofiber coatings on gold substrate for surface plasmon resonance. The results presented here reveal the potential use of nanofiber networks for various optoelectronic devices.

Amyloid fibrils aggregation is a key pathological feature of many severe degenerative disorders including Alzheimer’s disease and clinical dementia. Moreover, amyloids have been classified as intriguing molecules due to their exceptional strength, sturdiness and elasticity. However, physical models that explain the structural basis of these properties remain largely elusive, preventing the description of the link between their hierarchical structure and physical properties. Here we present an atomistic-based multiscale analysis based on computational materiomics, utilized to predict the structure of the two known polymorphous Alzheimer’s Aβ(1–40) amyloid fibers. We report an analysis of the energies, structural changes and H-bonding for varying amyloid fibril lengths, elucidating their size dependent properties. We also propose an explanation for the different stability of the two morphologies. A structural model of amyloid fibers with lengths of hundreds of nanometers at atomistic resolution is obtained. It predicts the formation of twisted amyloid microfibers in close agreement with experimental results. The approach used here provides a link between the fibril geometry, the chemical interactions and the most stable configuration, and resolves the issue of missing atomistic structures for long amyloid fibers.

A method for simply and controllably modifying the surface of polyaniline nanofibres is described. The technique can be used to attach substituents bearing both acid and amine functional groups, making the materials suitable for further modification. Acid/amine functionalisation is achieved by a simple reflux reaction and therefore is a quick and easily scalable process. The modified nanofibres maintain their ability to switch between different states displaying distinctly different properties, thus making them suitable for adaptive sensing applications. As an example, we demonstrate how biomolecules can be attached to these functionalised nanofibres, to produce conducting polymer-based biosensors.

Poly(3,4-ethylenedioxythiophene) (PEDOT) nanofibers were obtained by the combination of electrospinning and vapour-phase polymerization. The fibers had diameters around 350 ± 60 nm, and were soldered at every intersection, ensuring superior dimensional stability of the mats. The nanofiber mats demonstrated very high conductivity (60 ± 10 S/cm, the highest value reported so far for polymer nanofibers) as well as very interesting electrochemical properties, due to the porous and nanostructured nature of the electrospun mats. The mats were incorporated into all-solid flexible supercapacitors that showed interesting performances for applications where flexible and lightweight energy storage devices are required.

Measurement of elongational stresses, stereographic images of jet paths, innovative collection of fluid jets, and utilization of elongational flow for assembly or disassembly of particulate structures, the electron microscopic views inside nanofibers, and the morphological and crystallographic changes that occur during heating of the metastable electrospun fibers illuminate the growing versatility of the electrospinning process.

Single-walled carbon nanotube (SWCNT) and multi-walled carbon nanotube (MWCNT) were functionalized with 3,4-diaminobenzoic acid via “direct” Friedel-Crafts acylation reaction in PPA/P2O5 to afford ortho-diamino-functionalized SWCNT (DIF-SWCNT) and MWCNT (DIF-MWCNT). The resultant DIF-SWCNT and DIF-MWCNT showed improved solubility and dispersibility. To improve interfacial adhesion between CNT and polymer matrix, the grafting of ABPBI onto the surface of DIF-SWCNT (10 wt%) or DIF-MWCNT (10 wt%) was conducted by simple in-situ polymerization of AB monomer, 3,4-diaminobenzoic acid dihydrochloride, in PPA. The resultant ABPBI-g-MWCNT and ABPBI-g-SWCNT showed improved the mechanical and electrical properties.

Photoluminescent nanofibers (PLN) can be formed by combining electrospun polymeric nanofibers and luminescent particles such as quantum dots (QD). The physical properties of PLNs are dependent upon many different nanoscale parameters associated with the nanofiber, the luminescent particles, and their interactions. By understanding and manipulating these properties, the performance of the resulting optical structure can be tailored for desired end-use applications. For example, the quantum efficiency of quantum dots in the PLN structure depends upon multiple parameters including quantum dot chemistry, the method of forming the PLN nanocomposites, and preventing agglomeration of the quantum dot particles. This is especially important in solution-based electrospinning environments where some common solvents may have a detrimental effect on the performance of the PLN. With the proper control of these parameters, high quantum efficiencies can be readily obtained for PLNs. Achieving high quantum efficiencies is critical in applications such as solid-state lighting where PLNs can be an effective secondary conversion material for producing white light. Methods of optimizing the performance of PLNs through nanoscale manipulation of the nanofiber are discussed along with guidelines for tailoring the performance of nanofibers and quantum dots for application-specific requirements.

The manufacturing of magnetic PAN/Fe3O4 nanocomposite fibers is explored by an electrospinning process. The nanocomposite fibers were characterized by scanning electron microscopy (SEM). The magnetic properties of the nanoparticles in the polymer nanocomposite fibers are different from those of the dried as-received nanoparticles.

Electropolymerization of unsubstituted and substituted propylene - dioxythiophenes (i.e., ProDOT & ProDOT-Bz) on ( ˜7 μm diameter) single carbon fiber microelectrodes (SCFMEs) in different electrolytes resulted the network of nanopore structures. Surface morphology of coatings were investigated by Scanning Electron Microscopy (SEM), the attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) was used for the characterization . Electrochemical impedance spectroscopic investigation of these nanostructures has been indicated the capacitive behavior of electrode system. Data were used to simulate at applied potential and explained by equivalent circuit modeling.

Poly(vinylidene fluoride trifluoroethylene chlorofluoroethylene) (P(VDF-TrFE-CFE)) terpolymer nanorods embedded in Anodic Alumina Oxide( AAO) templates with pore sizes of 25, 70, and 200nm diameter were fabricated by extending the time of the wetting process. The instability of the wetting process induced the terpolymer infiltration into the inner space of tepolymer nanotubes, which formed mostly filled terpolymer nanorods. It was observed that all these nanorods embedded in AAO templates still possess relaxor ferroelectric behavior. The broad dielectric peak shifts progressively to higher temperatures with increasing frequency and the frequency- permittivity peak temperature fits well with the Vogel-Fulcher (V-F) relation. Moreover, the freezing temperature of the V-F relation is reduced, with the reduction of nanorod diameter. This indicates that the lateral confinement of the nanorods influences the relaxor ferroelectric behavior of the relaxor ferroelectric P(VDF-TrFE-CFE) terpolymer.

We have synthesized a series of ion exchange functionalized fibers (IXF) from polystyrene (PS) and polyacrylonitrile (PAN). To obtain strong-acid cation exchange fibers, polystyrene was sulfonated using specific sulfonation protocols. Micron sized fibers (average diameter of 100m) were then produced from the functionalized polystyrene using a single-screw extruder equipped with a 30 hole spinneret with orifice diameter of 0.5 mm with a precise screw speed of 5 rpm, pump speed of 15 rpm, and with a feed rate of 2.4 cc/min. The extruder zone temperature was kept at 250 – 270 °C. Fiber was drawn at 120 degree with a draw ratio of 2. Electrospinning of functionalized polystyrene was also carried out to produce ultrafine functionalized fibers of 100 nm in average diameter. We have also electrospun polystyrene and polyisoprene blended nanofibers to increase the strength of the resulting blend nanofibers compared to pure PS nanofibers. To synthesize weak-acid cation exchange fibers polyacrylonitrile (PAN) was electrospun and the nanofibers obtained were alkaline hydrolyzed with 2 N NaOH for 20 minutes at room temperature to convert nitrile bonds to carboxylate. Cation exchange capacity (CEC) of the microfibers and nanofibers was determined. Sulfonated PS microfibers show high CEC of 4.0 meq/gm compared to that of nanofibers with 2.5 meq/gm. CEC of blended nanofibers of PS and polyisoprene was 2.0 meq/gm. In case of PAN fibers, nanosized electrospun fibers were found to show a CEC of 1.5 meq/gm. Weak-base anion exchange fiber synthesis was undertaken using appropriate protocol and its CEC was measured. For all IXF synthesized, fiber diameter was measured using SEM, degree of functionalization was qualitatively determined using FTIR and ion exchange capacity was computed after mass balance on a binary exchange system after equilibrium.

The theoretical background and technical capabilities of the free liquid surface (nozzle-less) electrospinnig process is described. The process is the basis of both laboratory and industrial production machines known as NanospiderTM and developed by Elmarco s.r.o. Technical capabilities of the machines (productivity, nanofiber layer metrics, and quality) are described in detail. Comparison with competing/complementary technologies is given, e.g. nozzle electrospinning, nano-meltblown, and islets-in-the sea. Application fields for nanofiber materials produced by various methods are discussed. Consistency of the technology performance and production capabilities are demonstrated using an example of polyamide nanofiber air filter media.

Recent research indicates that nanophysical properties as well as biochemical cues can influence cellular re-colonization of a tissue scaffold. It has also been shown nanoscale elasticity can strongly influence cellular responses. In the present work, quantitative investigations of the elasticity of a nanofibrillar matrix scaffold that has demonstrated promise for spinal cord injury repair are compared with complementary transmission electron microscopy investigations, performed to assess nanofiber internal structures. Interpretive model improvements are identified and discussed.

Light impinging upon electrospun nanofiber substrates encounters a complex media where a multitude of factors controls the transmittance and reflectance of light through the structure. The chemical composition of the nanofiber plays a significant role in that it determines the index of refraction of individual fibers. However, the surrounding media (e.g., air, encapsulating polymer, etc.) also plays an equally important role. In addition, physical effects such as fiber diameter, fiber morphology, fiber packing density (i.e., structure void volume), and substrate thickness play a large role in determining the light management properties of nanofibers. Our research has demonstrated that the transmittance and reflectance of undoped nanofibers can be adjusted through proper manipulation of these factors. For example, similar electrospinning formulations can produce either highly transmitting or highly reflecting light structures depending upon fabrication parameters that impact the final properties of the nanofiber substrates. In addition, a degree of wavelength dependent reflectance and transmittance can be imparted simply by adjusting the physical properties of the nanofibers to promote preferential light scattering below selected frequencies. This paper provides an overview of various factors impacting the light management properties of nanofiber substrates and the importance of controlling these factors to meet end-use applications.

Due to the difficulty in handling nanofibers, little is reported and understood on the dry adhesion between electrospun nanofibers. In this study, we develop a technique to measure the dry adhesive forces between electrospun nanofibers. Of critical importance is the ability to mimic naturally occurring dry adhesion such as that between gecko's and spider's foot hairs and untreated surfaces. The adhesion test was performed on two poly(e-caprolactone) electrospun ultrafine fibers using a nanoforce tensile tester. It was found that the adhesive force per unit area increased with decreasing fiber diameter. The degree of crystallinity, order parameters of macromolecules in the amorphous region and crystallite orientation of the spun fibers were determined by the differential scanning calorimetry (DSC) and wide angle X-ray diffraction (WAXD). The high measured adhesion between single PCL fibers in comparison to other reported values was attributed to crystal orientation due to electrospinning and the increase of adhesive force per unit area with decreasing fiber diameter.