جستجوی مقالات مرتبط با کلیدواژه « Nanofibers » در نشریات گروه « مواد و متالورژی »

The primary objective of the current research is to produce polymeric nanofibers of chitosan and polyvinyl alcohol containing chicory plant extract and then evaluate their antibacterial effects. As remarked by numerous published articles, the chicory plant proved to be able to modulate the activity and growth of bacteria. For this reason, chicory plant extract was added to the fiber precursor in the amounts of 1, 2, and 3 %. Finally, the morphology and antibacterial properties of the resultant nanofibers were investigated. The results from Field Emission Scanning Electron Microscope (FESEM) confirmed the formation of uniform fibers whose diameters decreased from 144 nm to 95 nm with an increase in the amount of the extract in the sample. In addition, Energy Dispersive X-ray (EDX) and X-map analyses confirmed the presence of elements of carbon, oxygen, nitrogen, chlorine, potassium, sodium, and copper in the precursor of the fibers containing the extract and their uniform distribution. In this study, Fourier Transform Infrared Spectroscopy (FT-IR) helped identify the functional groups and chemical bonds in the synthesized nanofibers. According to the Ultraviolet-Visible thermometry (UV-VIS) results, one emission in the ultraviolet region with the wavelength of 263 nm and two emissions in the ultraviolet and visible regions with the wavelengths of 263 nm and 372 nm were observed in the absorption spectrum of nanofibers without and with the extract, respectively. examination of the antibacterial properties in the present study confirmed that upon increasing the amount of the extract in the sample, the antibacterial effect of the electrospun nanofibers would be intensified in exposure to both Escherichia coli and Staphylococcus aureus.

In this study, a waterproof hybrid nanofibrous membrane with breathability and high resistance to water penetration was prepared. For this purpose, polyurethane-poly(vinylidene fluoride) hybrid nanofibers with different ratios and with addition of silica nanoparticles were produced by electrospinning method. The effect of different ratios of the studied polymers on the morphology and performance of nanofibrous membranes such as breathability and waterproof properties were studied. Scanning electron microscopy and analysis of air permeability, hydrostatic pressure and water vapor permeability were used for this purpose. Morphological study of hybrid nanofibrous membrane shows the fabrication of uniform and bead-free fibers with average diameter of 60 to 80 nm. Moreover, increasing the ratio of PVDF polymer in nanofibrous membrane by 70% increased their air permeability and hydrostatic pressure. The results also show that the nanofibrous membrane containing 70:30 PVDF/PU, exhibits better breathability and waterproof properties, as its air permeability and water vapor permeability were obtained 68.6 mL/cm2.s and 2853 g/m2/day, respectively.

In this study, seven-layer nanofiber structures consisting of polycaprolactone/ chitosan polymers loaded with methotrexate and 5-fluorouracil anti-cancer drugs, for controlled drug delivery, were produced and evaluated. For this purpose, the second, fourth and sixth layers were loaded with drug and placed between the drug-free layers. The surface morphology of drug-free and drug-loaded nanofibers was investigated by scanning electron microscopy (SEM) and Fourier transform infrared spectrometry (FTIR) was used to study their chemical structure. The drug release rate in phosphate buffered saline (pH=7.4) and the released drug concentration were measured by spectrophotometry. Mechanical properties of single- and multi-layered samples were also investigated. SEM images showed formation of uniform and beadless fibers. FTIR spectrum confirmed presence of the drugs in the polymer mixture with no interaction. It was found that by increasing the chitosan content, a brittle structure with decreased elongation is formed. The release behavior of methotrexate and 5-Fluoracil drugs in neutral pH environment for 26 days was evaluated and the results exhibited a slow and sustained release.

In this study, polyurethane nanofibers containing carbon nanotubes modified with metal oxide nanoparticles including copper oxide and chromium oxide were prepared. First, carbon nanotubes were modified by hydrothermally (CNT-CuO-h) and ultrasonically (CNT-CuO-s) synthesized copper oxide nanoparticles, as well as chromium oxide, and then 12% polyurethane solution containing 0.7% modified carbon nanotube were electrospuned. Morphology and energy dispersive X-ray diffraction (EDX) results indicating the distribution and dispersion of metal oxide nanoparticles on carbon nanotubes, as well as the uniform distribution of bead-free nanofibrous composites. Moreover, structural analysis through Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction patterns (XRD) indicate the modification of carbon nanotube with copper and chromium oxides. Investigation of hydrogen sulfide adsorption on nanofibrous membrane containing modified carbon nanotubes and its comparison with nanofibrous membrane containing carbon nanotubes and activated carbon indicate a significant enhancement in gas adsorption capacity of samples containing carbon nanotubes modified with metal oxides. The results showed that adding only 0.7% (wt.%) carbon nanotube modified with copper oxide (CNT-CuO-h) to polyurethane nanofiber membranes increases the hydrogen sulfide adsorption capacity and gas breakthrough time by three times.

In this study, polyurethane foam was prepared using various nanostructures including polymer nanofibers, carbon nanotubes, and nickel oxide nanoparticles. Polyurethane, poly (methyl methacrylate) and poly (vinyl alcohol) nanofibers were first fabricated by electrospinning method and added to the foam during the formation of polyurethane foam along with carbon nanotube and nickel oxide nanoparticles. The morphology, mechanical properties and sound absorption behavior of the foam were evaluated using scanning electron microscopy (SEM), Instron an impedance tube. The results indicate that the nanofibers are uniform and free of beads, as well as the presence of these nanofibers within the pores and porosity of the foam. Polyurethane foam reinforced with polymer nanofibers also showed higher compressive strength than pure polyurethane foam. Sound absorption studies of foam showed that the addition of nanostructures improves the sound absorption efficiency of polyurethane foam in the frequency range of 250-610 Hz. Polyurethane foam reinforced with poly (methyl methacrylate) nanofibers and carbon nanotubes as well as nickel oxide nanoparticles exhibits the highest sound absorption at all frequencies, especially at low frequencies.

In this research, keratin (Kr)/ poly caprolactone (PCL)/ hydroxyapatite (HA) scaffold was made by electrospinning method. Then, the effect of HA nanoparticles on properties of scaffold B (Kr 33%, PCL 50% and HA 17%) and scaffold A (Kr 40% and PCL 60%) were studied. The surface morphology, functional groups on the surface of samples, porosity, and specific surface area were evaluated by Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectrophotometer (FTIR), liquid displacement method, and BET test, respectively. The mean diameter of fibers in samples A and B was measured 184 nm and 108 nm, respectively. Results showed that the specific surface area in scaffolds with HA nanoparticles was almost 2 times higher than that of the scaffold without HA. The biodegradability of scaffolds was examined in phosphate buffer solution (PBS) and the results showed an increase in the weight loss percentage of the scaffold B. The cell viability and adherence of osteosarcoma cell line (Saos-2) on the scaffold surface was observed via MTT assay and the results showed an increase in cell growth on PCL/Kr scaffolds with HA nanoparticles. Thus, scaffolds containing HA nanoparticles can be a good choice for tissue engineering applications.

The aim of this study was to fabricate carbon nanotube (CNT) and bioactive glass nanoparticles (BG) (at levels of 5 and 10 wt%) incorporated electrospun chitosan (CS)/polyvinyl alcohol (PVA) nanofibers for potential neural tissue engineering applications.The morphology, structure, and mechanical properties of the formed electrospun fibrous mats were characterized using scanning electron microscopy (SEM) and mechanical testing, respectively. In vitro cell culture of embryonal carcinoma stem cells (P19) were seeded onto the electrospun scaffolds. The results showed that the incorporation of CNTs and BG nanoparticles did not appreciably affect the morphology of the CS/PVA nanofibers. The maximum tensile strength (7.9 MPa) was observed in the composite sample with 5 %wt bioactive glass nanoparticles. The results suggest that BG and CNT-incorporated CS/PVA nanofibrous scaffolds with small diameters, high porosity, and promoted mechanical properties can potentially provide many possibilities for applications in the fields of neural tissue engineering and regenerative medicine.

In this paper, Nano fibers (Engelhard Corporation titanosilicate number 10 / polyacrylonitrile) ETS-10 / PAN, as a composite exchanger to absorb heavy metals, were synthesized and optimized. Several parameters were affected on this absorption. Results show that the optimization sizes of the Nano fibers are about 75 nanometers. Structures were analyzed by Scanning Electron Microscope (SEM) and Energy Dispersive X-Ray Analysis (EDAX). Furthermore, identification and measurement of the pore and absorbent surface to volume ratio was performed with BET analysis.

In this study, the polyacryliamodoxime (PAAO) powder was synthesized by treating the polyacrylonitrile (PAN) powder through chemical procedures, and used to hydrolyze the simulated nerve agent, i.e., dimethoate. GC-MS spectroscopy technique demonstrated the ability of PAAO powder to hydrolysis over 95% of dimethoate pesticide within 12 hours. Since the properties of substances in nano scale are improved, it was planned to synthesize PAAO nano fibers via two (i) conversion of PAN powder to PAAO powder and preparing its nanofiber; (ii) preparation of PAAO nanofibers from PAN nanofibers. Successful operation of the amidoximation was confirmed by FTIR technique. Thermal behavior of PAN and PAAO powders were investigated by thermogravimetric analyzer (TGA). SEM technique was used to study the morphology of PAAO nanofibers. SEM images revealed that PAAO nanofibers is uniform and bead-less, hence, it could be used as a coating for self–decontamination procedure.

Multiple nozzle electrospinning systems can be designed to increase both productivity and thickness for large scale nanofibers production. In the present study describes the results of the experimental investigation and modeling of multiple jets during the electrospinning of polyacrylonitrile (PAN) solutions. Several multiple nozzle electrospinning setups were tested. PAN solutions (15 w/v%) were electrospun varying the number of nozzles between 1 and 4. Nanofiber morphology was observed under a scanning electron microscopy (SEM). With increasing the number of nozzles in the electrospinning setup from 1 to 4, the average nanofibers diameter increased from 223±26 nm to 519±78 nm. The geometrical alignment and number of the nozzles showed significant effects on the average diameter and the divergence angle between jets. The divergence angle enlargement due to the increase of jets number from 2 to 4, made necessary to increase collector dimensions from 20cm×25cm to 40cm×45cm. It indicates that the interaction between the polymer jets from individual nozzles plays a great role in the electrospun nanofibers formation.

In the present study, electrospinning of polyvinyl alcohol (PVA) has been attempted to generate various nanofibers structures. The effects of polymer solution properties (e.g. Berry number (Be) and polymer concentration) on electrospinnability of the PVA solutions have investigated. Fiber morphology was observed under a scanning electron microscopy (SEM). For the polymer electrospun from low concentration (Be<2.5), polymer droplets have formed. The polymer electrospun from semi-dilute solution concentration (2.5

Keywords: Poly (vinyl alcohol), Nanofibers, Electrospinning, Concentration, Berry Number}