Electrical properties of ultrafine nylon-6 nanofibers prepared via electrospinning

We report on the preparation and electrical characterization of nylon-6 nanofibers via electrospinning technique. During electrospinning, the polymer solution became highly ionized and emerging out of the micro-tip syringe by forming mesh-like ultrafine nanofibers structure in between the main fibers. The resultant nylon-6 nanofibers were well-oriented with uniform structure. The diameter of the ultrafine nanofibers (7 to 40 nm) is one order less than those of main fibers (100 to 200 nm). The current-voltage (I-V) measurements revealed a linear curve with an occurrence of negative differential resistance (NDR) behavior. The existence of NDR region in the nylon-6 nanofibers can be attributed to the tunneling current through the ultrafine structures. The fabrication of nanofibers, in the form of ultrafine mesh-like form, is relatively fast and inexpensive, and it paves the way to build up of new dimension for nano device applications.     

Preparation and characterization of electrospinning PLA/curcumin composite membranes

In this paper, curcumin-loaded electrospinning Poly(lactic acid) (PLA) composite membranes were prepared. Curcumin with different contents (1, 3, and 5 wt%) was loaded to study its anticoagulation property as a drug-eluting stent. The structure of the composite membrane was analyzed by Fourier Transform Infrared (FTIR) spectroscopy, and the results suggested that both PLA and curcumin were present in the composite membrane without chemical reaction between them. Scanning electron microscopy (SEM) and related analysis revealed that the average diameters of composite nanofibers were between 756 and 971 nm with better uniformity in the range of the experiment, furthermore the average diameters of composite nanofibers decreased with the curcumin content increase; The in vitro anticoagulation behavior of curcumin-eluting stents was investigated through static platelet adhesion test, revealing that the anticoagulation property of composite membranes was superior to the pure PLA membrane, and the anticoagulation behavior significantly improved with increasing curcumin by dint of SEM observation.     

Fabrication and characterization of polyamide6-room temperature ionic liquid (PA6-RTIL) composite nanofibers by electrospinning

In the present work, polyamide6-room temperature ionic liquid (PA6-RTIL) composite nanofibers and membranes were successfully prepared for the first time by an electrospinning technique. The surface morphology, component analysis, mechanical properties, thermal properties and conductivity of the PA6-RTIL composite membranes were investigated by field-emission scanning electron microscope (FE-SEM), fourier transform infrared spectrometer (FT-IR), tensile testing, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and digit multimeter, respectively. The morphology, fiber diameter, mechanical strength of the obtained fibers can be controlled by changing experimental parameters for electrospinning, especially the content of RTIL in original electrospun mixture solution. The composite fibrous membranes showed ideal mechanical properties and significantly enhanced conductivity, which may be attributed to intrinsic high mechanical strength of PA6 and conductivity of RTIL.     

Evaluation of effective electrospinning parameters controlling gelatin nanofibers diameter via modelling artificial neural networks

The aim of this work was to evaluate the effective parameters for prediction of the electrospun gelatin nanofibers diameter using artificial neural network (ANN) technique. The various sets of electrospinning process including temperature, applied voltage and polymer and solvent concentrations were designed to produce pure gelatin nanofibers. The obtained results by analyzing Scanning Electron Microscopy (SEM) images indicated that the produced nanofibers diameter was in the range of 85 to 750 nm. Due to the volume of the data, k fold cross-validation method was used for data setting. Data were divided into the five categories and trained and tested using ANN technique. The results indicated that the network including 4 input variables, 3 hidden layers with 10, 18 and 9 nodes in each layers, respectively, and one output layer had the best performance in the testing sets. The mean squared error (MSE) and linear regression (R) between observed and predicted nanofibers diameter were 0.1531 and 0.9424, respectively. The obtained results demonstrated that the selected neural network model had acceptable performance for evaluating involved parameters and prediction of nanofibers diameter.     

Preparation of poly(vinyl alcohol)/ZrO2 composite nanofibers via co-axial electrospinning with higher ZrO2 particle content

Poly(vinyl alcohol) (PVA)/zirconium oxide (ZrO₂) composite nanofibers with a skin-core structure were prepared and the effect of ZrO₂ particle content on uniform web formation was investigated. The optimized polymer concentration, tip to collector distance, and applied voltage for electrospinning were 11 wt%, 12 cm, and 20 kV, respectively. Skin-core PVA/ZrO₂ composite nanofibers containing up to 12 wt% ZrO₂ were successfully prepared, but it was difficult to obtain PVA/ZrO₂ composite nanofiber webs via conventional electrospinning. Increasing the amount of ZrO₂ caused the morphology of the PVA/ZrO₂ composite nanofibers to become a non-uniform nanoweb with irregular nanofiber diameters. While it was difficult to obtain a uniform nanofiber web containing a content of ZrO₂ over 6 wt% for conventional electrospinning, a more uniform nanofiber web could be obtained at up to 9 wt% ZrO₂ using a skin-core dual nozzle. More uniform webs could also be obtained when ZrO₂ was in the skin rather than the core.     

Preparation and characterization of nanoscaled poly(vinyl alcohol) fibers via electrospinning

Nanoscaled PVA fibers were prepared by electrospinning. This paper described the electrospinning process, the processing conditions, fiber morphology, and some potential applications of the PVA nano-fibers. PVA fibers with various diameters (50–250 nm) were obtained by changing solution concentration, voltage and tip to collector distance (TCD). The major factor was the concentration of PVA solution which affected the fiber diameter evidently. Increasing the concentration, the fiber diameter was increased, and the amount of beads was reduced even to 0%. The fibers were found be efficiently crosslinked by glyoxal during the curing process. Phosphoric acid was used as a catalyst activator to reduce strength losses during crosslinking. Scanning electron micrograph (SEM) and differential scanning calorimetric (DSC) techniques were employed to characterize the morphology and crosslinking of PVA fibers. It was found that the primary factor which affected the crosslinking density was the content of chemical crosslinking agent.     

Preparation of self-clustering highly oriented nanofibers by needleless electrospinning methods

Polyacrylonitrile (PAN) oriented nanofibers were produced by homemade needleless electrospinning device. Spiral coils were adopted to replace the traditional spinning needles in this equipment. The tracks of multi-jets were controlled by adjusting the microcurrent during the eletrospinning process. The microcurrent value and the motion track of the spinning jet during the spinning process were observed, the fiber morphology and the mechanical properties of fiber membranes were measured. The results revealed that the average diameters of the electrospun fibers were increased from 490 nm to 740 nm. with the addition of organic salt. Meanwhile, the self-clustering phenomenon was obviously observed, and the mechanical properties of obtained fibers were also altered, the tensile strength was improved from 3.63 MPa to 23.90 MPa, while the strain decreased from 74.6 % to 27.1 %.     

Preparation and characterization of (polyurethane/nylon-6) nanofiber/ (silicone) film composites <Emphasis Type="Italic">via</Emphasis> electrospinning and dip-coating

This paper reports on the preparation and characterization of nanofibers and nanofiber/film composites fabricated by electrospinning and dip-coating. The polymers in this study consist of polyurethane, nylon-6, and silicone. Scanning electron microscopy (SEM), fiber distribution, X-ray diffraction (XRD) analysis, Fourier transform infrared spectroscopy (FTIR) and tensile tests were conducted. The electrospun nylon-6 nanofiber/dip-coated silicone film (dried for 5 min) showed the optimum tensile strength and strain results, showing an increase in tensile strength of 63 % compared to pure nylon-6 nanofiber alone. XRD and FTIR verified the presence of individual polymers in the composite matrix. The electrospun PU nanofiber produced the biggest fiber diameter, while electrospun nylon-6, and PU/nylon-6 produced uniform fiber diameters, with PU/nylon-6 obtaining very random and curved fiber morphology.     

Preparation and characterization of hair keratin/gelatin blend films

Abstract: Keratin solution was extracted from human hairs and used as subject for preparation of keratin/gelatin blend films. This study was aimed to explore the suitable method using for keratin extraction and extend to study the blend film properties. The blend films were prepared by simple evaporation method. After homogeneously mixed between keratin and gelatin solution at different ratios, the solution were placed on the plates and left in an oven at 40 degrees C for 3 days. All of the films were then analyzed for their morphology, secondary structures and thermal properties by using SEM, FTIR and TGA, respectively. The result from SEM images showed that native keratin films have the highest rough surface compared to other films. In addition, the smooth surface of films gradually increased when the gelatin content increased. Keratin blending with gelatin showed structural changes, especially at the absorption bands of 3300-2900 cm(-1) as well as the amide I, II and III regions. Moreover, thermal properties of the keratin films were enhanced by blending with gelatin. This study suggested that gelatin help to improve some properties of keratin while still remain its strength.     

Preparation,characterization of antibacterial PLA/TP nanofibers

Polylactic acid (PLA)/Tea polyphenol (TP) composite nanofilms were prepared using an electrospinning process. The mixed dichloromethane (DCM) and N,N-dinethylformamide (DMF) (70:30, v/v) was found to be the most suitable solvent for electrospinning. Various blends of PLA/TP solutions were formed. The morphology of the electrospun nano-scale fibers was investigated by scanning electron microscope (SEM), and the antibacterial performance was tested using shake flask method. The average diameter of the fibers is between 380 and 850 nm. It was found that the fiber diameter decreases as TP content increases, however the fibers may become brittle when the blend ratio of PLA and TP reached 50/50 (w/w). The antibacterial performance can be improved at the beginning when TP content increased. But it gradually gets impaired when TP content surpasses a certain value. The highest inhibitory rate against Escherichia coli and Staphylococcus aureus are 96.9 and 97.6 % respectively.     

Preparation and characterization of PVA/PU blend nanofiber mats by dual-jet electrospinning

A series of blend nanofiber mats comprising poly(vinyl alcohol) (PVA) and polyurethane (PU) were prepared by dual-jet electrospinning in various parameters. Orthogonal experimental design was used to investigate how those parameters affected on fiber diameters and fiber diameter distribution. Altogether three parameters having three levels each were chosen for this study. The chosen parameters were tip-to-collector distance (TCD), voltage and tip-to-tip distance (TTD). Fiber diameters, thermal properties, mechanical properties and hydrophilicity of the blend nanofiber mats were examined by scanning electron microscopy (SEM), thermogravimetric analysis (TGA), tensile test, contact angle and water absorption test, respectively. The results showed that the optimum conditions for PVA/PU blend nanofiber mats fabricated by dual-jet electrospinning were TCD of 20 cm, voltage of 18 kV and TTD of 4 cm. Besides, the thermal stability of PVA/PU blend nanofiber mats had been improved compared with pure nanofibers. Furthermore, the elongation and tensile strength of the blend nanofiber mats were significantly increased compared with pure PVA and pure PU, respectively. And the blend nanofiber mats exhibited well hydrophilicity.     

Preparation and characterization of Ceftazidime loaded electrospun silk fibroin/gelatin mat for wound dressing

Fabrication of Ceftazidime (CTZ) loaded silk fibroin/gelatin (SF/GT) nanofibers (NFs) without the loss of structure and bioactivity of CTZ was demonstrated by electrospinning method. The structure, morphology and mechanical properties of the electrospun SF/GT nanofibrous mats were characterized using FT-IR, SEM and DSC. The drug release profile of different electrospun fibers was analyzed using spectrophotometric method, and also diffusion method was applied to assess the antibacterial effect of NFs. Cell viability was evaluated by MTT assay. The results show that the average diameter of drug loaded NFs at the optimum polymer to drug feeding ratio (10:1) was 276.55±35.8 nm, while increasing the feeding ratio to 1:1 increases the average diameter to 825.02±70.3 nm. FT-IR of drug loaded NFs was revealed that CTZ was successfully encapsulated into NFs while viability study approved cytocompatibility of SF/GT NFs. CTZ was released from NFs during 6 h, and formation of inhibition zone in diffusion test demonstrated the antibacterial effect of drug loaded NFs. Altogether, the CTZ loaded SF/GT NFs can improve the drug effectiveness particularly in the prevention of post-surgical adhesions and infections for wound dressing.     

Fabrication of PVA-BaSO4 hybrid nanofibers and dispersion of BaSO4 particles via ultrasonic electrospinning

We reported the preparation and characterization of the poly(vinyl alcohol) (PVA)/BaSO₄ hybrid nanofibers prepared by normal and ultrasonic electrospinning, respectively. Compared to normal electrospinning, BaSO₄ particles in the resultant PVA/BaSO₄ hybrid nanofibers prepared by ultrasonic electrospinning were well-dispersed without severe agglomerations, as confirmed by scanning electron microscopy (SEM) analysis. X-ray diffraction (XRD) analysis indicated that typical crystalline peaks of PVA and BaSO₄ particles were dramatically decreased by ultrasonication during electrospinning. Moreover, the size of BaSO₄ aggregates became smaller.     

Isolation, characterization and biological evaluation of jellyfish collagen for use in biomedical applications

Fibrillar collagens are the more abundant extracellular proteins. They form a metazoan-specific family, and are highly conserved from sponge to human. Their structural and physiological properties have been successfully used in the food, cosmetic, and pharmaceutical industries. On the other hand, the increase of jellyfish has led us to consider this marine animal as a natural product for food and medicine. Here, we have tested different Mediterranean jellyfish species in order to investigate the economic potential of their collagens. We have studied different methods of collagen purification (tissues and experimental procedures). The best collagen yield was obtained using Rhizostoma pulmo oral arms and the pepsin extraction method (2-10 mg collagen/g of wet tissue). Although a significant yield was obtained with Cotylorhiza tuberculata (0.45 mg/g), R. pulmo was used for further experiments, this jellyfish being considered as harmless to humans and being an abundant source of material. Then, we compared the biological properties of R. pulmo collagen with mammalian fibrillar collagens in cell cytotoxicity assays and cell adhesion. There was no statistical difference in cytotoxicity (p > 0.05) between R. pulmo collagen and rat type I collagen. However, since heparin inhibits cell adhesion to jellyfish-native collagen by 55%, the main difference is that heparan sulfate proteoglycans could be preferentially involved in fibroblast and osteoblast adhesion to jellyfish collagens. Our data confirm the broad harmlessness of jellyfish collagens, and their biological effect on human cells that are similar to that of mammalian type I collagen. Given the bioavailability of jellyfish collagen and its biological properties, this marine material is thus a good candidate for replacing bovine or human collagens in selected biomedical applications.     

Fabrication of silver nanoparticle/polyvinyl alcohol/polycaprolactone hybrid nanofibers nonwovens by two-nozzle electrospinning for wound dressing

In this study, two biodegradable polymers, polycaprolactone (PCL) and polyvinyl alcohol (PVA) were used to fabricate nanofiber nonwovens (NFNs). Also, the silver nanoparticles (AgNPs) successfully reduced by using tea polyphenols (TP) and incorporated in the NFNs via electrospinning. The morphologies of the NFNs and AgNPs were analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), respectively. The PCL nanofibers and PVA nanofibers interweaved each other, and AgNPs with average diameter 1.53±0.15 nm were embedded in the PVA nanofibers. The properties of electrospun NFNs were characterized by pore property, swelling/weight loss, water contact angle, mechanical property, and antibacterial activity. The nanofibers cross-linked to each other forming the 3Dnetwork porous structure with diameter about 1-1.5 μm. Although the hydrophobic PCL was added in the hybrid NFNs, the NFNs still showed hydrophilic propriety, high swelling degree (i.e. swelling degree is 330 % for 48 h), and low weight loss (i.e. weight loss is 22.4 % for 48 h). Also, the hybrid PCL/PVA/AgNPs NFNs exhibited a suitable mechanical property for wound dressings (i.e. tensile strength is 4.27 MPa, and breaking elongation is 88 %). Moreover, the hybrid NFNs effectively inhibited growth of Escherichia coli and Staphylococcus aureus. In summary, this PCL/PVA/AgNPs NFNs may provide a promising candidate for accelerating wound healing.     

Electrospun meta-aramid/cellulose acetate and meta-aramid/cellulose composite nanofibers

Meta-aramid/cellulose acetate and meta-aramid/cellulose composite nanofibers were successfully prepared in this paper. There were some new interactions formed among composite ingredients and the beads of nanofibers decreased with increasing the weight proportion of ingredients and concentration of composite solution. The meta-aramid/cellulose acetate composite solution was more favorable for electrospinning because of its lower viscosity and surface tension than meta-aramid/cellulose composite solution, and the uniform nanofibers were obtained when the weight proportion of meta-aramid/cellulose acetate was larger than 1:2, however, it was feasible for meta-aramid/cellulose composite solution when the weight proportion of composite solution exceeded 4:1. The thermal property and mechanical property of composite nanofibers were improved after blending meta-aramid with cellulose acetate or cellulose.     

Preparation of electrospun LA-PA/PET/Ag form-stable phase change composite fibers with improved thermal energy storage and retrieval rates via electrospinning and followed by UV irradiation photoreduction method

In this paper, novel electrospun LA-PA/PET/Ag phase change composite fibers with different amount of Ag nanoparticles were prepared via the technique of electrospinning followed by UV irradiation method. The morphological structure, thermal energy storage properties, thermal energy storage and release rates of prepared LA-PA/PET/AgNO₃ and LA-PA/PET/Ag composite fibers were investigated by scanning electron microscope (SEM), high-resolution transmission electron microscope (HR-TEM), differential scanning calorimeter (DSC), and the measurement of melting and freezing times, respectively. The SEM images revealed that electrospun LA-PA/PET/AgNO₃ and LA-PA/PET/Ag composite fibers possessed the smooth morphologies with cylindrical shape. The corresponding average fiber diameters gradually decreased with increasing content of the AgNO₃ in the solutions, and slightly smaller than those of the LA-PA/PET composite fibers with oblate morphology and wrinkled surfaces. Yellow-brown coloration of electrospun LA-PA/PET/Ag phase change composite fibers were observed after UV irradiation treatment, which demonstrated that Ag ions were successfully reduced to Ag nanoparticles. The TEM images revealed that these reduced Ag nanoparticles were homogenously dispersed within the composite fibers. The results from DSC measurements indicated that the phase change temperatures and enthalpies of electrospun LA-PA/PET/Ag phase change composite fibers with different Ag content have not be influenced by the UVirradiation treatment. The thermal energy storage and release rates of electrospun LA-PA/PET/Ag phase change composite fibers were also improved due to the combination of reduced Ag nanoparticles. These UV-irradiated electrospun phase change composite fibers with excellent thermal energy storage properties can be acted as a novel form-stable PCMs for the applications related to storage and retrieval of thermal energy.     

Preparation of electrospun silk fibroin/Cellulose Acetate blend nanofibers and their applications to heavy metal ions adsorption

Silk fibroin (SF)/Cellulose Acetate (CA) blend nanofibrous membranes were prepared by electrospinning and their heavy metal absorbabilities were examined in an aqueous solution after ethanol treatment. The electrospun nanofibrous membranes were comprised of randomly oriented ultrafine fibers of 100–600 nm diameters. As a result of field emission electron microscope (FEEM), the anti-felting properties of the blend nanofibrous membranes were markedly improved after treatment with 100 % ethanol when SF was blended with CA. Metal ion adsorption test was performed with Cu²⁺ as a model heavy metal ion in a stock solution. The SF/CA blend nanofiber membranes showed higher affinity for Cu²⁺ in an aqueous solution than pure SF and pure CA nanofiber membranes. Especially, the blend nanofibrous membranes with 20 % content of CA had an exceptional performance for the adsorption of Cu²⁺, and the maximum milligrams per gram of Cu²⁺ adsorbed reached 22.8 mg/g. This indicated that SF and CA had synergetic effect. Furthermore, the parameters affecting the metal ions adsorption, such as running time and initial concentration of Cu²⁺, had been investigated. The results showed that the adsorption of the Cu²⁺ sharply increased during the first 60 min, the amount of metal ions adsorbed increased rapidly as the initial concentration increased and then slope of the increase decreased as the concentration further increased. This study provides the relatively comprehensive data for the SF/CA blend nanofibrous membranes application to the removal of heavy metal ion in wastewater.     

RGO/Nylon-6 composite mat with unique structural features and electrical properties obtained from electrospinning and hydrothermal process

In this work, the reduced graphene oxide (RGO) sheets were effectively uploaded through nylon-6 fibers using combined process of electrospinning and hydrothermal treatment. Good dispersion of graphene oxide (GO) with nylon-6 solution could allow to upload GO sheets through nylon-6 fibers and facilitate the formation of spider-wave-like nano-nets during electrospinning. GO sheets present on/into nylon-6 spider-wave-like nano-nets were further reduced to RGO using hydrothermal treatment. The impregnated GO sheets into nylon-6 nanofibers and their reduction during hydrothermal treatment were confirmed by FE-SEM, TEM, FT-IR and Raman spectra. The electrical characteristics of pristine nylon-6, GO/nylon-6 and RGO/nylon-6 nanofibers were investigated and it was found that RGO/nylon-6 composite mat had better electrical conductivity than others. The formation of spider-wave-like nano-nets as well as indirect route of incorporation of RGO sheets on electrospun nylon-6 mat may open a new direction for future graphene/polymer electronics.     

Preparation of PHEMA/nHAP nanocomposites via <Emphasis Type="Italic">in situ</Emphasis> polymerization in supercritical carbon dioxide for biomedical applications

Poly(2-hydroxyethylmethacrylate) (PHEMA)/hydroxyapatite (HAP) nanocomposites were synthesized through a new route involving nano-sized HAP (nHAP) particles or modified nHAP mixed with monomer 2-hydroxyethylmethacrylate via in situ polymerization in supercritical carbon dioxide (scCO₂). Fourier-transform infrared spectroscopy showed phosphate peak increased with nHAP content in composite. X-ray diffraction patterns of PHEMA/nHAP revealed the presence of crystallized nHAP. Thermogravimetric analysis showed that the ultimate nHAP content in PHEMA/nHAP composites is consistent with its initial amount. Scanning electron microscopy revealed that nanocomposite particles are much smaller than PHEMA particles. PHEMA/nHAP composites with average diameter of approximately 600 nm were obtained in scCO₂ with 94 % yield. Mechanical properties of PHEMA/nHAP nanocomposites were better than those of PHEMA, and compressive modulus and strength of composites with 30 wt.% nHAP were 193 and 29 MPa, respectively. Nanocomposite adsorption toward bovine serum albumin was evaluated, and results indicated that analyte adsorption amount can reach up to 282 mg/g.