Thermo-mechanical behavior of electrospun thermoplastic polyurethane nanofibers

Analysis of the thermo-mechanical behavior of electrospun thermoplastic polyurethane (TPU) block co-polymer nanofibers (glass transition temperature ∼−50 °C) is presented. Upon heating, nanofibers began to massively contract, at ∼70 °C, whereas TPU cast films started to expand. Radial wide-angle X-ray scattering (WAXS) profiles of the nanofibers and the films showed no diffraction peaks related to crystals, whereas their amorphous halo had an asymmetric shape, which can be approximated by two components, associated with hard and soft segments. During heating, noticeable changes in the contribution of these components were only observed in nanofibers. These changes, which were accompanied with an endothermic DSC peak, coinciding with the start of the nanofibers contraction, can be attributed to relaxation of an oriented stretched amorphous phase created during electrospinning. Such structure relaxation becomes possible when a portion of the hard segment clusters, forming an effective physical network, is destroyed upon heating.     

Largely improved toughness of poly(lactic acid) by unique electrospun fiber network structure of thermoplastic polyurethane

Oriented thermoplastic polyurethane (TPU) fiber and fiber network were first prepared by electrospinning. The as-prepared TPU fiber or fiber network was then pre-fixed in poly(lactic acid) (PLA)/TPU composite to improve the toughness of PLA. For comparison purpose, TPU/PLA composites with sea-island morphology were also prepared by traditional solution blending and mechanical blending. The results show that the toughness of PLA is greatly increased by the special pre-fixed oriented TPU fibers even at a low content, and the toughness is further increased by the TPU fiber network. Our results indicate for the first time that the toughening effect of special TPU fibers or fiber network is much better than that of traditional TPU with sea-island morphology. This study provides guidance to largely improve the toughness of PLA by designing the special phase morphology of TPU.     

Solvent degradation of nylon-6 and its effect on fiber morphology of electrospun mats

In this work, we studied solvent-induced polymer degradation and its effect on the morphology of electrospun fibers. Nylon-6 in formic acid solvent was allowed to degrade by simply allowing it to stand for a long time, and nanofibrous mats were fabricated by taking a fraction of this solution at different time intervals via electrospinning under the same electrospinning conditions. FE-SEM images of the mats indicate that the nanofiber diameter gradually decreased with the standing time of solution, and large numbers of true nano fibers (<50 nm in diameter) were obtained. MALDI-TOF analysis revealed that the formation of low-molecular weight ions was caused by solvent degradation. FT-IR, DSC, XRD, and TGA analyses of electrospun mats showed that some physical properties, such as bond strength, crystallinity, and thermal stability also depended on solvent degradation. The obtained sub-nanofibrous mat has potential applications in different bioengineering fields.     

Mechanical behavior of electrospun fiber mats of poly(vinyl chloride)/polyurethane polyblends

Various polyblends of poly(vinyl chloride) and polyurethane (PU) dissolved in a mixture of tetrahydrofuran and N,N‐dimethylformamide were produced by electrospinning, in different ratios, with several electrospinning conditions, and the relationship between morphology and mechanical behavior of the resulting fiber mats was examined in detail. The surface tension, viscosity, and electrical conductivity of polymer solutions affecting electrospinning were measured, and scanning electron microscopy (SEM) along with a universal testing machine were used to examine the family of polyblends under investigation. The SEM images demonstrated that point‐bonded structures in the fiber mats rose with increasing PU composition, and the mechanical properties of the fiber mats, as determined in a static tensile test, can be considered to have a strong effect by the point‐bonded structure. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1256–1262, 2003     

Phase morphology and mechanical properties of the electrospun polyoxymethylene/polyurethane blend fiber mats

Polyoxymethylene/thermoplastic polyurethane (POM/TPU) blends containing 10–30 wt % of TPU were electrospun using hexafluoroisopropanol as the solvent. The average fiber diameter increases with the increase in TPU content from 0.68 μm for neat POM fibers to 0.92 μm for POM/TPU 7:3 blend fibers due to the increase in solution viscosity. Core/sheath structure with the major component POM as the core and the minor component TPU as the sheath was observed by transmission electron microscopy and further confirmed by surface N contents of the blend fiber mats. The crystalline melting point and the degree of crystallinity of POM have no obvious change by coelectrospinning with TPU due to lack of interaction between POM and TPU as revealed by Fourier transform infrared spectroscopy. Tensile tests showed that the unusual high ductility of POM fiber mat could be further increased by coelectrospinning with 10 or 20 wt % TPU without significantly decreasing the stiffness and strength. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1853–1859, 2009     

Electrically conducting electrospun silk membranes fabricated by adsorption of carbon nanotubes

We present a simple method of obtaining electrically conducting electrospun silk non-woven membranes consisting of nanofibers with multi-walled carbon nanotubes (MWCNTs) adsorbed on their surface. Nanofibrous membranes with fibroin diameters of 460 ± 40 nm were formed from aqueous Bombyx mori fibroin solution by electrospinning. The MWCNTs adhered well to the surface of the highly porous silk nanofibrous membranes when Triton X-100 was used as the surfactant for the dispersion of the MWCNTs in aqueous media. The electrical conductivity of the membranes was 2.4 × 10⁻⁴ S/cm due to the presence of the MWCNTs on their surface. In addition, the strong interaction between the MWCNTs and nanofibers keeps them from separating each other, even after ultrasonication. The combination of the high conductivity of the membranes and the simple process used to fabricate them could lead to significant advances in the development of new materials, such as electromagnetic interference shielding or electrostatic dissipation membranes.     

Bacterial synthesis of magnetic Fe3O4 nanoparticles: Decolorization Acid Red 88 using FeNPs/Ca-Alg beads

The research studied the bacterial synthesis of magnetic iron oxide nanoparticles (FeNPs), their biological activity, and the biodegradation efficiency of Acid Red 88. An iron-resistant bacterial strain S2 was isolated from Choghart iron mine soil and selected to synthesize FeNPs. The phylogenetic analysis depended on 16S rDNA sequence comparison resolution and showed that strain S2 was 99.68% similar to Bacillus zhangzhouensis. FeNPs were identified by UV–Vis, FTIR, and XRD spectroscopy. SEM-EDX conclusions corroborated the size of FeNPs in the range of 20–70 nm in the rhombus form. The finding indicated that FeNPs had antimicrobial activity on tested bacteria. According to the brine shrimp lethality (BSL) test, FeNPs showed great anticancer activity with LC₅₀ value of 0.5 μg/ml. The biodegradation of Acid Red 88 was investigated separately by FeNPs/Ca-Alg beads and FeNPs powder. FeNPs/Ca-Alg beads decolorized Acid Red 88 with 100% efficiency after 24 h, while FeNPs powder decolorized Acid Red 88 with 100% efficiency after 72 h. Moreover, Ca-Alg beads were applied as control and could not decolorize the dye. Decolorization of Acid Red 88 using FeNPs/Ca-Alg beads was investigated by GC/MS analysis. In this analysis, no mass was found related to the initial mass of Acid Red 88. According to these conclusions, it can be inferred that the dye is completely decomposed. The toxicity of Acid Red 88 dye, and the decolorization products, was assessed using BSL and phytotoxicity test. The conclusions determined that Acid Red 88 dye had toxicity effect. Further, the decolorization products could not kill half of the shrimp due to their low toxicity and did not inhibit the germination of radish seeds.     

Thermodynamics of Hg2+ and Ag+ adsorption by 3-mercaptopropionic acid-functionalized superparamagnetic iron oxide nanoparticles

Journal of Thermal Analysis and Calorimetry - Superparamagnetic iron nanoparticles (SPION) have been functionalized with 3-mercaptopropionic acid (3-MPA), characterized and applied for the removal...     

Assembly of Pt nanoparticles on electrospun In2O3 nanofibers for H2S detection

In this paper, we presented a simple and effective solution route to deposit Pt nanoparticles on electrospun In₂O₃ nanofibers for H₂S gas detection. The morphology and chemical structure of the as-prepared samples were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectra (XPS). The results showed that large quantities of In₂O₃ nanofibers with diameters about from 60 to 100 nm were obtained and the surface of them was decorated with Pt nanoparticles (5–10 nm in size). The In₂O₃ nanofibers decorated by Pt nanoparticles exhibited excellent gas sensing properties to H₂S, such as high sensitivity, good selectivity and fast response at relatively low temperature.     

Effect of organoclay on thermal and dynamic mechanical properties of novel thermoplastic polyurethane nanocomposites prepared by melt intercalation technique

Polymer nanocomposites based on thermoplastic polyurethane (TPU) containing organophilic montmorillonite (OMMT) were prepared by melt compounding method followed by compression molding. Different percentage of organically modified nanoclays (1, 3, 5, 7, and 9 wt%) was incorporated into the TPU matrix in order to examine the influence of the nanofillers on nanophase morphology and materials' properties. The microstructure morphology of the nanocomposites was examined by transmission electron microscopy (TEM), energy dispersion X‐ray analysis (EDX), wide angle X‐ray diffraction (WAXD), and atomic force microscope (AFM). The observation established that the organoclay is homogeneously dispersed and preferentially embedded in the TPU soft segment phase. Significant enhancement in the thermal stability of the nanocomposites was observed with the addition of the OMMT under thermogravimetric analysis (TGA). Dynamic mechanical properties of the TPU nanocomposites were analyzed using a dynamic mechanical thermal analyzer (DMTA), which confirms that the addition of OMMT has a strong influence on the storage and loss modulus of the TPU matrix. Copyright © 2009 John Wiley & Sons, Ltd.     

The ultratrace detection of crystal violet using surface enhanced Raman scattering on colloidal Ag nanoparticles prepared by electrolysis

Highly active,stable and affordable surface enhanced Raman scattering(SERS) substrates were obtained by electrolyzing a mixture of AgNO_3(4×10~(-4) mol/L) and Na_3C_6H_5O_7·H_2O(6×10~(-5) mol/L) for 1,2,3 and 4h at 7V.With crystal violet(CV) as a test molecule,a portable Raman spectrometer with 785 nm laser excitation was employed to carry out the SERS detection.Colloidal Ag nanoparticles prepared by electrolyzing for 3 h with the particle size of(65±17) nm is a perfect SERS substrate for the ultratrace ...     

Y2O3:Eu (5 mol%) with Ag nanoparticles prepared by citrate precursor

Y₂O₃:Eu³⁺ (5 mol% Eu³⁺) and Y₂O₃:Eu³⁺ (5 mol% Eu³⁺) containing 1 mol% of Ag nanoparticles were prepared by heat treatment of a viscous resin obtained via citrate precursor. TEM and EDS analyses showed that Y₂O₃:Eu³⁺ (5 mol% Eu³⁺) is formed by nanoparticles with an average size of 12 nm, which increases to 30 nm when Ag is present because the effect of metal induced crystallization occurs. Ag nanoparticles with a size of 9 nm dispersed in Y₂O₃:Eu³⁺ (5 mol% Eu³⁺) were obtained and the surface plasmon effect on Ag nanoparticles was observed. The emission around 612 nm assigned to the Eu³⁺ (⁵D₀→⁷F₂) transition enhanced when the Ag nanoparticles were present in the Y₂O₃:Eu³⁺ luminescent material.     

Improved magnetic properties of self-composite SrFe12O19 powder prepared by Fe3O4 nanoparticles

Sintered polycrystalline strontium hexaferrite, which is one of the most widely used permanent magnetic materials, has been applied in many areas such as electrical and mechanical transductor devices. Improving the coercivity (H_cJ) of M-type strontium hexaferrite with a nominal composition SrFe₁₂O₁₉ (SrM) plays an essential role to adapt to many modern applications, but is limited by the process and purity of raw materials. In this work, we prepared SrM powders with different iron resources, sintering temperatures, and Fe/Sr atom ratios. It was found that using Fe₃O₄ nanoparticles with a Fe/Sr atom ratio of 12 at 1100 °C performed the self-composites with 70% nano-size and 30% micro-size, which had the best performance. The coercivity reaches 348.9 kA/m, which is improved compared to pure SrM obtained by other iron resources in the solid-state method. This process shows a unique formation mechanism and the resulting self-composite microstructure eventually causes enhancement in the properties, which provides a new way for high-performance hexaferrites.     

Synthesis and characterization of new HgS nanoparticles prepared by Hg(II)-triazole-3-thiol as precursor

Nine Hg(II) complexes, [Hg(DiphtS)₂(L-L)](2–7) {where, HDiphtS = 4,5-diphenyl-1,2,4-triazole-3-thiol; L-L = bis(diphenylphosphino)ethane (dppe) (2); 1,3-bis(diphenylphosphino)propane (dppp)(3); 1,4-bis(diphenylphosphino)butane (dppb)(4); 1,1′-bis(diphenylphosphino)ferrocene (dppf)(5); 2,2′-bipyridine (Bipy)(6) and 1,10-phenanthroline (Phen)(7) } or [Hg(DiphtS)₂(L)₂] (8–9) {where L = triphenylphosphine (Ph₃P) (8) and triphenylphosphine sulphide (Ph₃PS) (9)}, have been prepared form the reaction of [Hg(DiphtS)₂](1) with phosphine or amine as co-ligands. Then characterized by the IR, NMR (¹H and ³¹P) spectroscopy, elemental analysis, molar conductivity. The results supported the monodentate behaviour of HDiphtS ligand in all complexes (1–9) in anion form through the sulfur atom. Complexes 1, 2 and 6 have been used as single source precursors for the preparation of ethylene-diamine capped HgS-nanoparticles. Powder X-ray diffraction (PXRD), and scanning electron microscopy (SEM), have been used to characterize the HgS nanoparticles.     

Quenched electrochemiluminescence of Ag nanoparticles functionalized g-C3N4 by ferrocene for highly sensitive immunosensing

In this paper, a novel sandwich electrochemiluminescence (ECL) immunosensor was constructed by ferrocene for quenching Ag nanoparticles functionalized g-C₃N₄ (Ag@g-C₃N₄) emission. The prepared Ag@g-C₃N₄ had strong and stable ECL signals compared to pure g-C₃N₄ and primary antibody (Ab₁) can be immobilized on Ag@g-C₃N₄ by adsorption of Ag nanoparticles. Ferrocene carboxylic acid (Fc-COOH) labeled secondary antibody was immobilized on Au doped mesoporous Al₂O₃ nanorods (Au@Al₂O₃–Fc-COOH@Ab₂) as labels through adsorption ability of Au toward proteins. After a sandwich-type immunoreaction, a remarkable decrease of ECL signal was observed due to the ECL quenching of Ag@g-C₃N₄ by Au@Al₂O₃–Fc-COOH@Ab₂. As a result, the change of ECL intensity has a direct relationship with the logarithm of CEA concentrations in the range of 1 pg mL⁻¹–100 ng mL⁻¹ with a detection limit of 0.35 pg mL⁻¹ (S/N = 3). Additionally, the proposed immunosensor shows high specificity, good reproducibility, and long-term stability.     

The dependence of persistent phosphorescence on annealing temperatures in CaTiO3:Pr nanoparticles prepared by a coprecipitation technique

Red emitting phosphors of CaTiO₃:Pr³⁺ nanoparticles with size ranging from 6 to 95 nm have been prepared by a coprecipitation technique and structurally characterized by X-ray diffraction, energy dispersive spectroscopy and scanning electron microscopy. The fluorescence and phosphorescence of CaTiO₃:Pr³⁺ nanoparticles as a function of annealing temperature are investigated. It is found that fluorescence intensities monotonously increase with increasing temperature. However, a maximum in phosphorescence with the increase of annealing temperature occurs for the sample prepared at 700 °C. Based on the measurement of fluorescence emission, fluorescence excitation and reflectance spectra as well as time decay patterns of fluorescence and phosphorescence, it is demonstrated that the dependence of fluorescence and phosphorescence on annealing temperature originates from the decrease of surface defects with the increase of temperature.     

Hydrophilic Fe3O4 nanoparticles prepared by ferrocene as high‐efficiency heterogeneous Fenton catalyst for the degradation of methyl orange

Hydrophilic Fe₃O₄ nanoparticles were prepared with ferrocene as an iron source via the thermal decomposition method and their catalytic response towards methyl orange was investigated. The effects of the pH, temperature, H₂O₂ dosage, catalyst dosage and initial dye concentration on the degradation of methyl orange were researched in detail. Furthermore, the stability of the catalyst was evaluated by measuring the degradation rate in eight successive cycles. The study demonstrates that methyl orange can be completely degraded i.e., a 99% degratation rate was obtained within 3 min. This excellent catalytic activity is attributed to the small size and good dispersibility of the nanoparticles, which stimulate the rapid and massive generation of reactive oxygen species in the heterogeneous Fenton reaction. In addition, the magnetic separation of the catalyst offers great prospects for fast and economical decontamination of dye polluted water.     

Improvement of interfacial adhesion performance of the kevlar fiber mat by depositing SiC/TiO2/Al2O3/graphene nanoparticles

Modern world seeks dramatic progress in composite materials use in numerous applications. Scientists worldwide are researching on fabricating new composites and attempting to have more applications using these materials. Serious attempts have also been taken to improve the properties of these materials. In this circumstance, a conscious attempt has been made in this present work that studies the effect of SiC/TiO₂/Al₂O₃/ graphene nanoparticles (NPs) deposition on Kevlar fiber. In this process, SiC/TiO₂/Al₂O₃/ graphene NPs have been deposited on Kevlar fiber by dip coating process. For the analysis, physical observation has been performed well at first which confirms nanoparticle deposition on the fiber and formation of adhesive bonding. SEM analysis followed by surface topography has been conducted to observe and further analysis of nanoparticle deposition. Atomic bonding mechanism shows how chemical bonding between fiber and nanoparticles. TGA analysis shows thermal improvement of the fiber by NPs deposition where graphene with binder makes 21.6% improvement in decomposition temperature. Tensile strength and young’s modulus of binder inclusion coated kevlar fabric are improved up to 26% and 5.7%, respectively. Finally, the IR-spectra confirms successful deposition of nanoparticles on the fiber.     

In situ generation of Ag nanoparticles during photopolymerization by using newly developed dyes-based three-component photoinitiating systems and the related 3D printing applications and their shape change behavior

Silver nanoparticles (AgNPs) play a crucial role in biology and medical research as their extensive and efficient antibacterial activity and high electrical and thermal conductivity. However, the generation of them with a certain morphology under mild conditions (under air, solvent-free, room temperature, etc.,) is still a huge challenge. Herein, a simple one-step method is proposed to generate AgNPs in situ at room temperature under air by combining the photopolymerization process with the formation process of AgNPs within a few minutes. In detailed, 12 different dyes based on 2,5-diethylene-cyclopentan-1-one were first synthesized and used as high-performance type II photoinitiator. When using in conjunction of bis-(4-tert-butylphenyl) iodonium hexafluorophosphate (Iod) and ethyl 4-dimethylaminobenzoate (EDB), they can effectively boost the free radical photopolymerization (FRP) of polyethylene glycol diacrylate (PEG-DA) and the cationic photopolymerization (CP) of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate (EPOX) upon irradiation with LED@405 nm. Furthermore, all the formulations containing/without AgNPs can be successfully used to perform the direct laser write experiment. However, even if all of the obtained 3D patterns exhibited reversible swelling performance and shape-memory effects caused by swelling and dehydration for the access to 4D printing, the presence of AgNPs will affect these properties.     

Magnetic poly(glycidyl methacrylate)-based microspheres prepared by suspension polymerization in the presence of modified La0.75Sr0.25MnO3 nanoparticles

With the aim of preparing new magnetic poly(glycidyl methacrylate) (PGMA) microspheres suitable for magnetic separation, La_0.75Sr_0.25MnO₃ nanoparticles were selected as a core material. In order to improve their compatibility with PGMA, the surface of the nanoparticles was treated with penta(methylethylene glycol) phosphate methacrylate (PMGPMA) as a stabilizer. Subsequently, the nanoparticles were encapsulated by the suspension polymerization of glycidyl methacrylate (GMA) resulting in a relatively homogeneous distribution of La_0.75Sr_0.25MnO₃ nanoparticle aggregates inside the polymer microspheres. Microspheres in the size range of a hundred micrometers with a broad particle size distribution were obtained. PMGPMA can be considered to be an efficient compatibilizer between La_0.75Sr_0.25MnO₃ nanoparticles and PGMA. Both PMGPMA-coated La_0.75Sr_0.25MnO₃ nanoparticles and magnetic PGMA microspheres were characterized in terms of morphology, particle size, composition and magnetic properties by the appropriate methods, such as X-ray diffraction, FTIR spectroscopy, thermogravimetric analysis (TGA), transmission electron microscopy (TEM), light microscopy and SQUID magnetometry.