The most known utilization of catalysts is the use of metal nanoparticles on the electrode of a Proton Exchange Membrane Fuel Cell on which the electrode consists of catalyst, either Pt or Pd on a carbon support. In this research porous polyacrylonitrile (PAN) based carbon nanofibers comprising nanosized metal particles are produced using electrospinning technique. By the optimization of polymer chemistry, electrospinning variables and carbonization procedures the effective metal size is reduced up to 5 nm. It is still possible to enhance the catalytic performance by decreasing the metal concentration and/or enable using less catalytic material for equivalent catalytic performance which can lead to cost savings, amongst other advantages.

Using the electrospinning technique, we have prepared [Ru (pic) 2 (dmso) 2] doped-polyethylene oxide nanofibers for ultraviolet sensing. The diameter of the as-prepared fibers is in the range of 1μm-100nm. These fibers change color from pale yellow to orange when exposed to ultraviolet light (wavelength∼350nm) and return to their original color after approximately 2-3 days. The intensity of the color increases with an increased time of exposure to UV. The color changing behavior in the nanofibrous mat is almost the same as that in cast films prepared from the same solutions. The scanning electron microscope (SEM) studies of the fibers show that the morphology of the fibers remains unchanged after exposure to UV.

An integrated data acquisition/actuator control system is developed to conduct experiments investigating the fundamental dynamics for different operating conditions in an electrospinning system. The relation between measured variables (fiber current, whipping angle, jet length, and expulsion cone volume) to the resulting fiber diameter distribution is analyzed.

Tin oxide microfibers were created through electrospinning using a precursor solution consisting of poly(ethylene oxide) (PEO) and chloroform (CHCl3) which was then mixed with its tin precursor, dimethyldineodecanoatin (C22H44O4Sn). Since the conductivity of SnO2 is affected by any chemisorbed oxygen molecules on its surface, this semiconductor has high potential for use as a gas sensor for both oxidizing and reducing gases. Due to the fact that a greater surface area will produce gas sensors with improved sensitivity, work is underway to reduce the fibers size into the nanoscale range. Thus, this study explores various electronic transport characteristics—such as the conductivity and magnetoresistance—of the tin oxide microfibers. Additionally, the composition and phase of the fibers were characterized through XRD and Raman spectroscopy.

Electrospinning and dc sputtering techniques were combined for the formation of a variety of nano-to-microscale structures of palladium metal. Polyethylene fibers created by electrospinning were used as templates for the dc sputtering of palladium on top of them. Heating the fibers to 320 °C in air eliminated the central polymer core (fugitive phase) resulting in the formation of open and closed core fibers, depending on the amount of Pd previously deposited. The formation of the structures is best explained as a consequence of sputtering being a line-of-sigh technique. Palladium is preferentially sputtered on top of the fiber part facing the target, resulting in a non-uniform deposition. Furthermore, it is proposed that the deposition of palladium on top of the fibers results in the nucleation of palladium crystals growing outward of the surface and producing interesting nanoscale features observed resembling thorns and scales.

A novel template-less method for polymerization of ethyl 2-cyanoacrylate to form an intrinsically nanofibrous polymer is investigated. Effect of the anionic initiator used for polymerization is examined to explain the mechanism of formation of nanofibers or film of polymer. A suitable classification of the initiators is established based on the Hard Soft Acid Base principle to explain the mechanism. Infrared analysis, SEM and Gel permeation chromatography is utilized for characterization of the different polymer samples.

Electrospinning has been thought of as an effective, low cost technique for producing nanofibers for use in gas sensor applications with nanofibers of tin oxide showing particular promise in this area. Critical to the success of tin oxide in these applications are nanowires with a rutile phase structure and well defined current-voltage characteristics which requires controlled fiber diameters. This paper reports on the characterization of the pre and post sintered fibers deposited via electrospinning of two different tin precursor chemicals, dimethyl dineodecanoate tin and dimethyl dichloro tin, both spun within a polyethylene oxide / chloroform binder system. Both tin precursor systems were evaluated at different concentration levels to investigate morphological changes due to concentration. Mats of fibers were spun on silicon wafers and sintered at 600°C for 2 hours. Morphology was characterized by optical microscope while chemical composition was determined via Raman spectrometry. Fibers of dimethyl dineodecanoate tin were found be ∼30μm in diameter and to have considerable component separation upon deposition. After sintering, SnO2 islands were found but there was no fiber appearance. Fibers of dimethyl dichloro tin were found to be ∼10μm in diameter and lacked the component separation seen in the other tin precursor system with some SnO2 domains found directly inline with initial fiber deposition. Comparison of results from both systems shows that the interaction of the polymer and tin precursor is of paramount importance for development of micro- or nanosized ceramic wires deposited by electrospinning.

The synthesis of poly(9,9-dioctylfluorene) conjugated polymer nanowires using the method of solution assisted wetting of nanoporous alumina membrane templates is reported. Polymer nanowires (approx. 109 per template) with a diameter of approx. 200 nm are obtained. Photoluminescence from isolated nanowires fluidically-aligned at glass substrates is found to be dominated by emission from the planar beta-phase of the polymer. The wires also exhibit polarized light emission suggestive of axial alignment of beta-phase segments within the nanowires. Dense arrays of aligned nanowires exhibiting anisotropic emission are also demonstrated.

Electro-hydro-dynamic (EHD) compound jets, with diameters in the micro and nanometric size range, from conical menisci of two co-flowing liquids, is a consolidated platform for the production of nanofibers with inner structure, in a process so-called coaxial electrospinning or co-electrospinning. In contrast to other multi-step template based procedures, the EHD methodology is much more simple and general since, firstly, a solid template is needless and, secondly, the process is seldom affected by the chemistry of the liquids. This gentle process allows selecting the liquid precursors depending on the application sought for the nanofibers. Here, we review different products obtained by this EHD technique: (1) solid and hollow carbon nanofibers from different precursors (polyacrylonitrile, polyvinylpyrrolidone and lignin), (2) nanofibers of biocompatible polymers encapsulating liquids in the form of beads, (3) spinning nanofibers of alginate and (4) in-fiber encapsulation of active microgels.

Electrically conducting fibers of polyaniline doped with Camphorsulfonic acid PAn.HCSA in the Polyethylene Oxide (PEO) matrix were prepared using the non-mechanical electrospinning technique. The morphology of the fibers was studied using the scanning electron microscope (SEM) and Transmission electron microscope (TEM), showing a uniform thickness along the fiber length. The fibers had a diameter ranging from 800nm to 2μm. The electrical conductivity of the non-woven fibrous mat and the cast film was measured using the four-point probe method, for different concentrations of Pan.HCSA in the blend. Some possible factors affecting the electrical conductivity of the fibers/films were discussed.

The strain rate mechanical behavior of 12-micron long polymeric nanofibers was investigated. Experiments were carried out by a novel method that employs a MEMS-based leaf spring load cell attached to a polymeric nanofiber that is drawn with an external PZT actuator. The elongation of the fiber and the deflection of the load cell were calculated from optical microscopy images by using Digital Image Correlation (DIC) and with 65 nm resolution in fiber extension. The nanofibers were fabricated from electrospun polyacrylonitrile (PAN) with MW = 150,000 and diameters between 300-600 nm. At strain rates between 0.00025 s−1 to 0.025 s−1 the fiber ductility scaled directly with the rate of loading while the tensile strength was found to vary non-monotonically: At 0.00025 s−1 material relaxations allowed for near-uniform fiber drawing with up to 120% ductility and 120 MPa maximum tensile strength. At the two faster rates the tensile strength scaled with the rate of loading but the fiber ductility was the result of a cascade of localized deformations at nanoscale necks with relatively constant wavelength for all fiber diameters.

Herein we report the patterning of large conducting polymer nanofiber mats of the polyterthiophene precursor, into regular micron scale arrays of smaller mats each of which has the potential of being independently addressed. These fiber grids, micro mats of conducting polymer fibers, were prepared by the combined techniques of electrospinning, soft photolithography, and solid state electrochemical crosslinking. The micro size mats are shown to retain their electrochromic behavior, subject to expected degradation in air as reported in the literature. Our contribution to the investigation of conducting polymers in display technology is oriented towards processibility and preparation of regular conducting polymer structures.

Electrospinning, a polymer processing technique to create nanofibrous membranes, has been used to fabricate fibrous membranes from solution and melt phases showing supramolecular order. Wormlike micellar phases of low molar mass amphiphiles, including the phospholipid mixture asolectin, were electrospun under normal conditions to form micron-sized fibers. From the melt, well defined phospholipid 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine was electrospun into a similar fibrous membrane. Additionally, thermoreversible physical crosslinks were used to prepare fibers from low molecular weight, star-shaped poly(D,L-lactide) under melt electrospinning conditions.

We present a simple method for fabricating high aspect-ratio polymer nanostructures on a solid substrate by sequential application of molding and drawing of a thin polymer film. In this method, a thin polymer film is prepared by spin coating on a solid substrate and the temperature is raised above the polymer¡¯s glass transition while in conformal contact with a poly(urethane acrylate) (PUA) mold having nano-cavities. Consequently, capillary forces induces deformation of the polymer melt into the void spaces of the mold and the filled nanostructure was further elongated upon removal of the mold due to tailored adhesive force at the mold/polymer interface. The optimum value of the work of adhesion at the mold/polymer interface ranged from 0.9 to 1.1 times that at the substrate/polymer interface. Below or above this range, a simple molding or detachment occurred, corresponding to earlier findings.

Electrospinning has been used to prepare poly(vinyl alcohol) (PVA) nanofibers, with diameters ranging from 1 micron down to 20 nm, that contain dispersions of isolated, well-aligned, single wall carbon nanotubes (SWNTs). The nanofibers were characterized by Raman spectroscopy and single radial breathing modes (RBMs) were found for the SWNTs in the nanofibers indicating debundling of the original SWNT ropes. Moreover a split G' band for some nanotubes and the results of polarized Raman spectroscopy were consistent with the presence of isolated SWNTs, highly aligned along the nanofiber axes.

The determination of the behavior of the jet path in the vicinity of the onset of the primary electrical bending instability is important for the orderly collection of the nanofibers produced by electrospinning. A stable jet was observed with a high frame rate, short exposure time video camera. The collection process was complicated but predictable within limits, so the design and creation of some two or three dimensional structures of nanofibers is feasible, if the considerations described below are incorporated into the design and production processes.

The fluid jet in the straight segment of the path, and the more solid nanofibers in the coils of the primary electrical bending instability were collected on stationary and moving surfaces. The diameter and characteristic path of the jet depended on the exact distance between the orifice and the collector, if other parameters were not changed. The moving surfaces caused the various coils that were collected to be displaced rather than superimposed. The fiber collected on the moving surfaces preserved a record of the electrical and mechanical instabilities that occurred. If the straight segment was very fluid, the jet formed a series of small sessile drops on the collector, but when the jet was more solid, buckling occurred and produced small, complicated loops close to point at which the jet hit the surface. Buckling was observed during collection of the straight segment and the first coils of the electrically driven electrical bending instability. A moving inclined collector was used to collect the fibers. Surface velocities were up to about 5 meters per second. These velocities are commensurate with the velocities at which the solidifying jet approached the surface. A variety of structures of loops, both conglutinated and not, associated with the instabilities were created.

The jets used in this work were formed from solutions of polyethylene oxide, nylon-6, poly lactic acid, and other polymers. Several solvents were used for some of the polymers, and details of the jet path changed when the solvent or the concentration changed. The jets issued from a pendent drop on a glass capillary with an orifice diameter of about 160 microns. A potential difference in the range of 500 to 13,000 volts was applied between the orifice and the collector. The distance from the orifice to the grounded collector varied from 1 mm to 30 cm. Interference colors associated with jet diameters around 10 microns were observed in the straight segment. The color patterns were stable, indicating that the process variations were small.