Immobilization of gold nanoparticles on poly(methyl methacrylate) electrospun fibers exhibiting solid‐state surface plasmon effect

In this study, the surface plasmon effect of Au nanoparticles was successfully realized in the solid state by embedding the Au nanoparticles on the surface of the transparent polymer fibers for the first time. Electrospinning a poly(methyl methacrylate) (PMMA) and HAuCl₄ mixture followed by a wet chemical reduction, the gold nanoparticles were formed on the PMMA nanocomposite electrospun fibers in a well‐distributed manner to give photostable purple color. The Au nanoparticles were all sphere shaped with an average diameter of 12 nm. Specifically, simply adjusting HAuCl₄ salt concentration in the electrospinning solution, it is able to control the electrospun fiber diameter and gold nanoparticle content in the resulting PMMA/Au nanocomposite fibers. Therefore, the developed method described herein is simple and effective for the large volume production of PMMA/Au nanocomposite fibers. Copyright © 2011 John Wiley & Sons, Ltd.     

Effects of diameter and surface area of electrospun nanocomposite fibers on electromagnetic interference shielding

The effects of variation in average diameter and surface area of nanocomposite fibers on electromagnetic interference (EMI) shielding of multi-walled carbon nanotubes (MWCNTs)/polyvinylpyrrolidone (PVP) fibers were investigated in this paper. The EMI shielding effectiveness of electrospun nanocomposite fibers were measured in the X-band frequency range 8.2–12.4 GHz. The electrical conductivity and EMI shielding behaviors of the nanocomposite fibers were reported as function of average diameter and surface area of MWCNTs/PVP nanocomposite fibers. The electrical conductivity measurements demonstrate using thinner nanocomposite fibers results in a lower limit of electrical resistivity, better electrical conductivity performance. The EMI shielding efficiency of thinner nanocomposite fibers increased up to 42 dB. The EMI shielding data for MWCNTs/PVP nanocomposite fibers with various average diameter and surface area showed that absorption was the major shielding mechanism and reflection was the secondary shielding mechanism. It can be related to higher specific surface area of thinner electrospun MWCNTs/PVP nanocomposite fibers that means more surface area for radiative scatter and absorption leading to higher EMI shielding performance.     

Polycaprolactone composites with TiO(2) for potential nanobiomaterials: tunable properties using different phases

TiO(2) nanoparticles of different phases play a key role in property alteration of nanocomposite fibers. Polycaprolactone (PCL)/TiO(2) composite fibers were prepared using the electrospinning method. Pure anatase and rutile phases were synthesized using the sol-gel route for nanocomposite synthesis. The Effect of nanoparticle phases on crystallinity of fibers and interaction with polymer molecules have been studied using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, morphology through SEM, surface properties using BET method and wetting property of fibers commencing from contact angle measurement. Biocompatibility and biodegradation of hybrid materials have been studied in simulated body fluid (SBF) and phosphate buffer (PBS), respectively. The anatase phase with smaller particle dimensions exhibited significant improvement of most of the properties as compared to composites made of the rutile phase. Better interaction between polymer chain and anatase particle PCL-A nanocomposite fibers leads to better mechanical property and biocompatibility vis-à-vis PCL-R and pristine PCL fibers. Biocompatibility of PCL nanocomposite has been testified through proliferation of fibroblast cell and its adhesion; MTT (3-(4,5-dimethythiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay demonstrates good proliferation rate for cells on PCL-A nanocomposite fibres.     

A Polyethylene Nanocomposite Prepared via In‐Situ Polymerization

A novel organic/inorganic nanocomposite of polyethylene (PE) was prepared via in‐situ coordination polymerization. The Ziegler‐Natta catalyst was first supported on the surface of silicate nanowhiskers to subsequently initiate the polymerization of ethylene on the surface of these nanowhiskers. The nanowhiskers were encapsulated by polyethylene and became reinforcement fibers of the composite. The strong interaction between the uniformly dispersed nanowhiskers and the resin matrix resulted in the formation of a kind of organic/inorganic network providing good mechanical properties.     

Structure and nanomechanical characterization of electrospun PS/clay nanocomposite fibers

Electrospinning has been emerging as one of the most efficient methods to fabricate polymer nanofibers. In this paper, PS/clay nanocomposite fibers with varying diameters were electrospun onto solid substrates. The fiber diameters were adjusted from 4 microm to 150 nm by changing the solution concentration. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM) were used to characterize the fiber morphology. Shear modulation force microscopy (SMFM) was utilized to investigate the surface nanomechanical properties of electrospun fibers as a function of the fiber diameter and temperature. In the absence of clay, no change in T(g) was observed, even though a large increase of shear modulus below the glass transition temperature was found. This effect was postulated to result from the molecular chain alignment during electrospinning. The addition of functionalized clays to the spinning solution produced fibers with a highly aligned montmorillonite layer structure at a clay concentration of 4 wt %. Clay agglomerates were observed at higher concentrations. The existence of clay further enhanced the shear modulus of fibers and increased the glass transition temperature by nearly 20 degrees C.     

Microscopic Evaluation of Acid-Etched Optical Fibers

Abstract

Optical and scanning electron microscopy were used to examine the changes in the surface morphology of optical fibers as a result of acid etching. The resulting surface modifications are modeled and the resulting structures are considered as alternatives to conventional fibers for chemical sensor development. Hydrofluoric acid (HF) etching has been performed on the tips of flat-end graded index fibers, and spherical-end graded and step index fibers. The acid treatment caused the formation of a cone-shaped hollow in the center of graded index fiber tips. This structure provides a surface area enhancement of up to 5.3-fold over untreated fibers. In addition, this cone-shaped cavity provides a sub-nanoliter reservoir in which reagent can be held at the sensing tip of the fiber. Spherical-end fibers provide surface area increases of up to 35-fold compared to flat-end fibers. With spherical-end step index fibers, HF etches the cladding, but not the core, thereby providing an even greater surface area for reagent immobilization. The potential utility of these acid etched fibers for the development of fiber-optic chemical sensors (FOCS) is discussed.     

Poly(methyl methacrylate)/silica nanocomposite fibers by electrospinning

Uniform poly(methyl methacrylate) (PMMA)/silica nanocomposite fibers containing up to 20 wt % silica were prepared by electrospinning. The electrospun solutions were prepared by mixing a solution of PMMA in dimethyl formamide (DMF) with colloidal silica in methyl ethyl ketone (MEK). The average fiber diameter decreases from 2.49 μm to 1.69 μm when 20 wt % silica is incorporated as a result of considerably increased solution conductivity, although the solution viscosity increases significantly, which should result in opposite effect. Thinner fibers (down to 350 nm) can be obtained by changing DMF/MEK proportion and by the addition of an ammonium salt. Nano‐sized silica particles (10–40 nm) distributes homogeneously in the fibers, as revealed by transmission electron microscopy. Furthermore, the incorporation of silica nanoparticles can change the thermal properties and surface wettability of the fiber mats. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1211–1218, 2009     

Alignment effect of attapulgite on the mechanical properties of poly(vinyl alcohol)/attapulgite nanocomposite fibers

Poly(vinyl alcohol) (PVA)/attapulgite (AT) nanocomposite fibers have been prepared by wet spinning. The morphology and mechanical properties of the modified PVA fibers have been characterized with transmission electron microscopy, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), birefringence measurements, and mechanical testing. The PVA/AT nanocomposite fibers show much higher tensile strength, initial modulus, and work to break than pure PVA fibers with the same draw ratio. SEM observations demonstrate that the AT nanorods can align orderly along the fiber axis by stretching and have good adhesion to the fiber matrix. The results of birefringence measurements prove that the modified fibers have higher orientation than pure PVA fibers after stretching. The results of DSC analysis indicate that the crystallinity of the PVA fibers can be increased by the addition of AT. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1995–2000, 2006     

Polyaniline/graphene oxide nanocomposite as a sorbent for extraction and determination of nicotine using headspace solid-phase microextraction and gas chromatography–flame ionization detector

A solid-phase microextraction fiber was prepared by polyaniline/graphene oxide nanocomposite as sorbent on the surface of a platinized stainless steel wire using electrospinning technique. The nanocomposite structure was characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. The polyaniline/graphene oxide nanocomposite fiber was used for the determination of nicotine from tobacco samples using headspace solid-phase microextraction method and gas chromatography–flame ionization detection. Influential experimental variables on the extraction efficiency of nicotine, such as extraction time and temperature, humidity and desorption conditions, were evaluated and optimized. Under the optimal experimental conditions? the limit of detection, linear dynamic range, intraday and inter-days precisions were found to be 0.01 μg g^?1, 0.05–700 µg g^?1 (R²?=?0.996), 6.9 and 8.1%, respectively. Comparison of the polyaniline/graphene oxide nanocomposite sorbent with polyaniline and commercial fibers shows longer durability, larger capacity and higher extraction efficiency. The polyaniline/graphene oxide nanocomposite fiber was successfully applied for the determination of nicotine in tobacco samples.     

Polythiophene/hexagonally ordered silica nanocomposite coating as a solid‐phase microextraction fiber for the determination of polycyclic aromatic hydrocarbons in water

A highly porous fiber coated with polythiophene/hexagonally ordered silica nanocomposite was prepared for solid‐phase microextraction (SPME). The prepared nanomaterial was immobilized onto a stainless‐steel wire for the fabrication of the SPME fiber. Polythiophene/hexagonally ordered silica nanocomposite fibers were used for the extraction of some polycyclic aromatic hydrocarbons from water samples. The extracted analytes were transferred to the injection port of a gas chromatograph using a laboratory‐designed SPME device. The results obtained prove the ability of the polythiophene/hexagonally ordered silica material as a new fiber for the sampling of organic compounds from water samples. This behavior is due most probably to the increased surface area of the polythiophene/hexagonally ordered silica nanocomposite. A one‐at‐a‐time optimization strategy was applied for optimizing the important extraction parameters such as extraction temperature, extraction time, ionic strength, stirring rate, and desorption temperature and time. Under the optimum conditions, the LOD of the proposed method is 0.1–3 pg/mL for analysis of polycyclic aromatic hydrocarbons from aqueous samples, and the calibration graphs were linear in a concentration range of 0.001–20 ng/mL (R² > 0.990) for most of the polycyclic aromatic hydrocarbons. The single fiber repeatability and fiber‐to‐fiber reproducibility were less than 8.6 and 19.1% (n = 5), respectively.     

Syndiotactic poly(propylene)/organoclay nanocomposite fibers: influence of the nano‐filler and the compatibilizer on the fiber properties

Melt spinning of nanocomposites prepared from syndiotactic poly(propylene) (sPP) and organolayered silicate (M‐ODA), containing bound octadecyl ammonium chains, was investigated. The influence of the nano‐filler reinforcement and the role of the addition of maleic anhydride grafted isotactic poly(propylene) (iPP‐g‐MA) as compatibilizer with respect to the fiber proportion was examined. The presence of nano‐filler, the drawing ratio, and the compatibilizer addition afforded increased tenacity of the fibers. Only in the presence of the compatibilizer high drawing ratio of the sPP nanocomposite fibers was achieved. Transmission electron microscopy (TEM) was applied to monitor morphology development during nanocomposite fiber spinning in the presence and the absence of the compatibilizer. Copyright © 2005 John Wiley & Sons, Ltd.     

Electrospinning of poly(trimethylene terephthalate)/carbon nanotube composites

Poly(trimethylene terephthalate) (PTT) nanocomposites containing carbon nanotubes (CNTs) with different surface structure and aspect ratio were prepared by melt compounding for electrospinning. The dispersion state of the CNTs in the composites was then examined utilizing rheology tools. The results show that carboxylic surface functionalized CNTs present better dispersion in the matrix than hydroxy surface functionalized CNTs because the former has stronger affinity to the PTT. Besides surface functionalization, the aspect ratio of CNTs is also vital to their final dispersion. The CNTs with lower aspect ratio are dispersed as individuals or small bundles while those with higher aspect ratio are dispersed mainly as flocs with large hydrodynamic radius, showing higher effective volume fraction. The presence of CNTs has a large influence on the morphologies of electrospun fiber and on the appearances of CNTs in the fibers. In the presence of CNTs with lower aspect ratio, continuous composite fibers are obtained. But the structure of those continuous fibers highly depends on the surface group of CNTs. Carboxylic surface functionalized CNTs are well embedded by the PTT and oriented along the fiber axis during electrospinning, leading to bead-free and uniform fiber morphology; while hydroxy surface functionalized CNTs show tortuous conformations with less orientation in the fibers, and as a result, the obtained fibers show beaded and misshaped morphologies. In the case of higher aspect ratio, however, the CNTs prefer to exist as entanglements or knots in the streamlines, and thereby only beaded or even uncontinuous fibers are obtained. Therefore, the formation and fiber morphology of PTT/CNT composite fibers obtained by electrospinning strongly depend on the surface functional groups of the CNTs, as well as on the CNT structure.     

Structure, morphology, thermal stability and carbonization mechanism studies of electrospun PA6/Fe-OMT nanocomposite fibers

In the present work, Fe-montmorillonite (Fe-MMT) was synthesized by hydrothermal method, and then was modified by cetyltrimethyl ammonium bromide (CTAB). The polyamide 6 (PA6)/organic-modified Fe-montmorillonite (Fe-OMT) nanocomposite fibers were prepared by a facile compounding and electrospinning. The catalyzing carbonization studies of the Fe-OMT based on PA6 nanocomposite fibers were performed. It was found from High-resolution electron microscopic (HREM) observations that the silicate clay layers were well dispersed within the nanocomposite fibers and was oriented along the fiber axis. The Scanning electron microscopic (SEM) images indicated that the nanofibers were randomly distributed to form the fibrous web and the Fe-OMT additives decreased the diameters of nanocomposite fibers. The Thermogravimetric analyses (TGA) revealed that the loading of the Fe-OMT led to the crosslinking of the PA6, promoted the charred residue yield and catalytic graphitization effect. The structure and morphology of the purified charred residue, characterized by XRD, HREM, Selected area electron diffraction (SAED) and Laser Raman spectroscopic (LR), approved further the presence of graphite sheets. The possible catalyzing carbonization mechanisms included: (1) catalyzing effect of the Fe³⁺, which promoted the crosslinking of polymer, (2) Hofmann degradation of the Fe-OMT, whose degraded products had also positive role in promoting crosslinking reactions, (3) gas barrier properties of the nano-dispersed silicate clay layers stopped or reduced the releases of the pyrolytic products, which was dehydrogenated and aromatized to form graphite.     

Introduction of a biowaste/graphene oxide nanocomposite as a coating for a metal alloy based SPME fiber: Application to screening of polycyclic aromatic hydrocarbons

The present study introduces a high efficiency metal alloy-based solid-phase microextraction (SPME) fiber coated with a green biowaste nanocomposite of chicken feet yellow membrane mixed with graphene oxide (CFYM/GO). An Al/Cr commercial heating element (aluchrom, AC) has been selected as the fiber substrate and designed as coiled form (CAC-SPME) to enhance its extraction and pre-concentration capacity. The fabricated fiber, CAC-SPME/CFYM/GO, has been employed for the extraction and pre-concentration of some commonly seen PAHs in different standard/real samples prior to their high performance liquid chromatography- ultraviolet (HPLC-UV) analyzing. The synthesized materials and the fibers surface were characterized by field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, Fourier-transform infrared spectroscopy analysis and Brunauer-Emmett-Teller surface area analysis. Under the optimized experimental conditions, low detection limits (LOD, 0.039–0.30 µg L^–1), wide linear ranges (LR, 0.13–643 µg L^–1) and good relative recoveries (RR, 76.20–105.60%) were achieved for all the target analytes. The materials applied to prepare this fiber were low-priced and accessible and also eliminated the need for expensive coating substances. In addition, using of the AC alloy substrate was increased the fiber physicochemical resistance and solved the breakage drawback of the conventional SPME fibers. Moreover, simple fabrication, high rigidity, long service life and high extraction capacity were some of the other advantages of the suggested fiber. Therefore, the proposed method can be utilized successfully for the routine analysis of PAHs in different matrixes.     

The mechanical properties of plasma‐treated carbon fiber reinforced PA6 composites with CNT

The aim of this work is the evaluation of the effects of plasma treatment and the addition of CNT on the mechanical properties of carbon fibre/PA6 composite. A powder impregnation process with integrated inline continuous plasma of carbon fibers was used to produce CF/PA6 composite. CF/PA6 composite was processed into test laminates by compression moulding, and interface dominated composite properties were studied. The tensile and impact strength of composites containing CNT and plasma‐treated carbon fibres improved obviously. The tensile strength of nanocomposite largely increases with the increasing of the CNT content and then decreases when the CNT content is over 2%. The hydroxyl groups of the fibers surface are in favor of the wettability of carbon fibers by the polar matrix resin, which is resulting in a further interaction of the fiber surface with the curing system of the matrix resin.     

静电纺丝法制备超细聚苯乙烯纳米纤维

采用静电纺丝方法制备了超细聚苯乙烯纤维, 通过向溶液中添加有机胺盐并降低溶液浓度将纤维的平均直径降至100 nm, 并研究了盐的添加量对纤维直径的影响.     

Controlling electrospun nanofiber morphology and mechanical properties using humidity

Electrospinning is a fiber spinning technique used to produce nanoscale polymeric fibers with superior interconnectivity and specific surface area. The fiber diameter, surface morphology, and mechanical strength are important properties of electrospun fibers that can be tuned for diverse applications. In this study, the authors investigate how the humidity during electrospinning influences these specific properties of the fiber mat. Using two previously uninvestigated polymers, poly(acrylonitrile) (PAN) and polysulfone (PSU) dissolved in N,N‐Dimethylformamide (DMF), experimental results show that increasing humidity during spinning causes an increase in fiber diameter and a decrease in mechanical strength. Moreover, surface features such as roughness or pores become evident when electrospinning in an atmosphere with high relative humidity (RH). However, PAN and PSU fibers are affected differently. PAN has a narrower distribution of fiber diameter regardless of the RH, whereas PSU has a wider and more bimodal distribution under high RH. In addition, PSU fibers spun at high humidity exhibit surface pores and higher specific surface area whereas PAN fibers exhibit an increased surface roughness but no visible pores. These fiber morphologies are caused by a complex interaction between the nonsolvent (water), the hygroscopic solvent (DMF), and the polymer. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Ascorbic acid as a mediator and template for assembling metallic nanoparticles

In this paper we report the results on the use of L-ascorbic acid (AA) in assembling metal nanoparticles (NPs) into three-dimensional fibrous structures. The degradation product of AA leads to the formation of fibrous structures, which has been used as a template for deposition of metal NPs such as Au, Pt, and Ag. We also report that AA can be used as the reducing agent in generating Au NPs. The spontaneous fiber formation and formation of Au NPs by AA have been coupled to generate fibers made up of composite of Au NPs and the polymer from the degradation products of AA. These fibers appear in the form of a fiber bundle with branched structures having overall dimensions on the order of several millimeters. They have typical widths of 1-4 microm with length of each segment of fiber bundle on the order of 40 microm. The composite fiber bundle has been found to be electrically conducting with surface resistivity on the order of 2.16x10(3) Omegacm. UV-vis spectroscopy, X-ray diffraction, transmission and scanning electron microscopic measurements were used to establish the formation of fibrous structures in the medium.     

Evaluation of liquid ammonia treatment on surface characteristics of hemp fiber

In this study, we investigated the effects of liquid ammonia treatment on the surface characteristics of hemp fibers. We determined the elemental composition, morphological structure, roughness, and wettability of fiber surface using techniques such as electron spectroscopy for chemical analysis, scanning electron microscopy, atomic force microscopy, and contact angle measurements. The lignin coverage on the hemp surface was calculated from the O/C ratio and the C₁ content. The results show that lignin removal from the fiber surface was significantly greater than that from the fiber bulk. After the treatment, the O/C ratio of hemp fibers increased, and cellulose was exposed. The proportion of O₂ species that contributed to formation of hydrogen bonds increased; this further increased the number of hydrophilic groups in the hemp fibers, improving the fiber wettability. The liquid ammonia treatment did not change the large dislocation structures in hemp fibers, but the removal of noncellulosic materials from the fiber surface increased the roughness of the fiber surface.     

On the indirect polyelectrolyte titration of cellulosic fibers. Conditions for charge stoichiometry and comparison with ESCA

The effect of electrolyte (NaHCO3) concentration on the adsorption of poly-DADMAC (poly-diallyldimethylammonium chloride) onto cellulosic fibers with different charge profiles was investigated. Surface carboxymethylated fibers were obtained by grafting carboxymethyl cellulose (CMC) onto the fiber surface and bulk carboxymethylated fibers were obtained by reacting the fibers with monochloroacetic acid. It was shown that nonionic interactions do not exist between cellulose and poly-DADMAC, rather electrostatic interactions govern the adsorption. Charge stoichiometry prevails under electrolyte-free conditions, whereas surface charge overcompensation occurs at higher electrolyte concentrations. It was shown that charge stoichiometry prevails if the thickness of the electric double layer kappa(-1) was larger than the mean distance between the charges on the fiber surface, as predicted by polyelectrolyte adsorption theories, taking lateral correlation effects into account. In a second set of experiments the ESCA technique served to independently calibrate the polyelectrolyte titrations for determining the surface charge of cellulosic fibers. Various molecular masses of poly-DADMAC were adsorbed to carboxymethylated fibers having different charge profiles. The adsorption of low M(w) poly-DADMAC (7.0 x 10(3)), analyzed by polyelectrolyte titration, was about 10 times higher than that of the high M(w) poly-DADMAC (9.2 x 10(5)). Despite the difference in accessibility of these two polyelectrolytes to the fiber cell wall, ESCA surface analysis showed, as expected, only slight differences between the two polyelectrolytes. This gives strong credibility to the idea that surface charge content of cellulosic fibers can be analyzed by means of adsorption of a high-molecular-mass cationic polymer, i.e., by polyelectrolyte titration.