Structurally modified electrospun poly(methyl methacrylate) nanofibers as advanced host matrices for PbS quantum dots

The present work deals with the studies of the host matrix nature of pure and structurally modified surface roughened and coaxial hollow electrospun poly(methyl methacrylate) (PMMA) nanofibers to lead sulphide (PbS) quantum dots. The various structural and molecular analyses conducted on these samples proved the advancements and structural modifications made in the properties of pure PMMA nanofibers by electrospinning and selective dissolution. The successful incorporation of the quantum dots to pure and structurally modified PMMA nanofibers and hence the host matrix nature of these nanofibers is proved by different spectral analyses of the samples. The coaxial hollow PMMA nanofibers are found to be the best host matrix among these PMMA nanofibers as proved by the optical studies of the samples. Photoluminescence analyses of the samples showed the influence of these quantum dots on the optical properties of PMMA nanofibers. It is observed here that, the quantum dots enhance the intensity of coaxial hollow PMMA nanofibers to about four times than its virgin form. The pure and structurally modified PMMA nanofibers incorporated with PbS quantum dots are proved to be efficient for the degradation of methylene blue dye where coaxial hollow PMMA nanofibers incorporated with PbS quantum dots is the best.     

Modification of thermoplastic polyurethane nanofiber membranes by in situ polydopamine coating for tissue engineering

To improve the interaction between cells and scaffolds, the appropriate surface chemical property is very important for tissue engineering scaffolds. In this work, the dopamine (DA) was first introduced into thermoplastic polyurethane (TPU) matrix to obtain TPU/DA nanofibers by electrospinning. Subsequently, the TPU@polydopamine (PDA) composite nanofibers with core/shell structure were fabricated by in situ polymerization of PDA. In comparison with TPU nanofibers, the uniformization of PDA coating layer on the surface of TPU/DA composite nanofibers significantly increased due to the addition of DA, which used as the active sites to guide the PDA particles accumulated along with the fiber direction. The hydrophilicity and water uptake ability of TPU@PDA composite nanofibers were larger than those of TPU nanofibers. The TPU@PDA composite nanofibers possess excellent comprehensive mechanical properties of high strength, stiffness, elasticity, and recoverability because of the hydrogen bonding occurrence between PDA and DA, as well as between PDA and TPU matrix. The attachment and viability of mouse embryonic osteoblasts cells (MC3T3-E1) cultured on TPU@PDA composite nanofibers were obviously enhanced compared with TPU nanofibers. Those results suggested that the modified TPU@PDA composite nanofibers have superior mechanical and biological properties, which promoting them potentially useful for tissue engineering scaffolds.     

Surface functionalization of polymer nanofibers by silver sputter coating

The surface properties of polymer nanofibers are of importance in many applications. In this study, the electrospun polyamide nanofibers were used as substrates for creating functional coating on the nanofiber surfaces. A direct current (DC) sputter coating was used to deposit functional silver nanofilm onto the nanofibers. Atomic force microscopy (AFM) and environmental scanning electron microscopy (ESEM) were employed to study the topography and chemical composition of the nanofibers, respectively. The AFM results indicate a significant difference in the morphology of the nanofibers before and after the sputter coating. The observations by AFM also show the change in the morphology of the nanofibers with coating time. A full energy dispersive X‐ray analysis (EDX) mounted on the ESEM was also used to detect the elemental composition of the functional nanofibers. EDX examination reveals the change in the chemical compositions of the nanofiber surfaces. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 2006     

Prussian blue nanoparticles potentiostatically electrodeposited on indium tin oxide/chitosan nanofibers electrode and their electrocatalysis towards hydrogen peroxide

Chitosan (CS) nanofibers were successfully used to modify indium tin oxide (ITO) electrode by electrospinning technique. Then, Prussian blue (PB) nanoparticles were electrodeposited on the CS nanofibers by potentiostatic technique in an acidic solution containing single ferricyanide. By this method, direct synthesis of PB nanoparticles on the nanofibers that were used for modifying electrode came true. Transmission electronic microscopy (TEM) showed that the average size of PB nanoparticles was about 50 nm. Selected-area electron diffraction (SAED) showed diffusive diffraction spots, indicating the mosaic structure of the PB nanoparticles on the CS nanofibers. X-ray powder diffraction (XRD) displayed the long-range disorder of CS nanofibers and demonstrated the formation of PB nanoparticles. Results of the scanning electron microscope (SEM) images indicated that the PB nanoparticles could be electrodeposited on the CS nanofibers. The amount of the PB nanoparticles on the CS nanofibers increased with increasing potential value of the electrodeposition. In addition, the cyclic voltammetric response displayed two characteristic redox couples of PB. The modified electrode exhibited electrocatalytic activity towards reduction of H₂O₂.     

Electrochemical synthesis and optical properties of helical polyaniline nanofibers

Helical polyaniline (PANI) nanofibers were facilely synthesized via a direct electrochemical method without using any template in the presence of (1S)-(+)-camphor-10-sulfonic acid (d-CSA) or (1R)-(−)-camphor-10-sulfonic acid (l-CSA) as the dopant. The helical morphologies of the PANI nanofibers prepared from potentiostatic deposition were confirmed with SEM and TEM. The helical PANI nanofibers induced by d-CSA and l-CSA exhibited mirror-imaged circular dichroism spectra in the UV-vis range, indicating the stereochemical selectivity of the electrochemical polymerization. The colors and optical activities of these nanofibers can be maintained on an indium-tin oxide (ITO) coated electrode with a dedoping/redoping treatment. The optical activities of the helical PANI nanofibers reversibly varied with different oxidized forms, which were easily controlled by the different potentials applied to the nanofibers.     

Structurally modified poly(methyl methacrylate) electrospun nanofibers as better host matrix for noble metal nanoparticles

Poly(methyl methacrylate) (PMMA) nanofibers are proved as good host matrix for various nanomaterials. Here, the possibilities offered by the process of electrospinning are exploited for the production of pure and structurally modified surface roughened and coaxial hollow PMMA electrospun nanofibers with unique advantages and surface characteristics, which is proved through various structural analyses. The host matrix nature of these pure and structurally modified surface roughened and coaxial hollow PMMA nanofibers to gold nanoparticles (AuNPs) are proved through different structural and morphological analyses. The host matrix nature of pure and structurally modified surface roughened and coaxial hollow PMMA nanofibers to AuNPs are compared with that of pure PMMA nanofibers by comparing their structural and optical properties. It is found here that, the surface roughened PMMA nanofibers act as better host matrix with more uniform distribution of particles and intensity enhancement than the pure and coaxial hollow PMMA nanofibers. Pure and coaxial hollow PMMA nanofibers show almost two times enhancement in intensity while the surface roughened PMMA nanofibers show almost five times enhancement in intensity after incorporating AuNPs. The host matrix nature of PMMA nanofibers is thus proved to be improved by making structural modifications on PMMA nanofibers in a simple and cost-effective way. This makes them more suitable and adaptable in their applications. This superior property of surface roughened PMMA nanofibers over pure PMMA nanofibers can be used in all the application fields of PMMA nanofibers like optical works, catalytically supporting agents, antibacterial supporting systems and so on.     

Functionalization of polyamide 6 nanofibers by electroless deposition of copper

Polyamide 6 (PA6) nanofibers were prepared via electrospinning. The electrospun PA6 nanofibers were functionalized using electroless deposition technique. Oxygen low temperature plasma treatment was applied to substitute the conventional roughening process using concentrated sulfuric acid-potassium dichromate. The deposition of copper (Cu) on the PA6 nanofibers was characterized using scanning electron microscopy (SEM), atomic force microscopy (AFM), and energy dispersive X-ray spectroscopy (EDX). The observations revealed the uniform coating of the PA6 nanofibers with thin films of Cu. It was also found that the surface conductivity of the PA6 nanofibers was significantly improved by the Cu deposition. The combination of electrospinning and electroless deposition will provide a new approach to producing the functional nanofibers for various applications.     

Biocompatible Smart Matrices Based on Poly (3,4-ethylenedioxythiophene)-Poly (N-isopropylacrylamide) Composite

The study investigated the use of composite of conducting poly(3,4-ethylenedioxythiophene) and temperature responsive poly(N-isopropylacrylamide) nanofibers as scaffold for tissue engineering application. The nanofibers of PNIPAm and PEDOT-PNIPAm composite were fabricated using electrospinning technique. FTIR was used to check the chemical structure of the composite while the conducting nature of the composite material was investigated by means of cyclic voltammetry. The average diameter of the PNIPAm and the composite nanofibers was investigated by using scanning electron microscopy, which indicates that the composite has some what more average diameter than the PNIPAm nanofibers alone. The biocompatibility of the material was studied by seeding L929 fibroblast cells on the nanofibers surface. It was seen that PEDOT-PNIPAm composite nanofibers shows highest cell growth and % live of around 98% indicating the use of these nanofibers as scaffold for the tissue engineering application.     

Rapid hemostasis by nanofibers of polyhydroxyethyl methacrylate/polyglycerol sebacic acid: An in vitro / in vivo study

Porous nanofibers were prepared from a combination of polyglycerol sebacate (PGS) and polyhydroxyethyl methacrylate (PHEMA) and loaded with tranexamic acid (TA) using the electrospinning method. The nanofibers were optimized for their morphology, diameter size, porosity, TA loading, release profile and mechanical behavior. Their cytotoxicity was studied based on 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide assay on L929 cells. The hemostasis control on a tail-cut model in rats was investigated. The best formulation contained 35% of the total polymers, 20% PGS and 10% TA in proportion to the total polymer quantity. These nanofibers had 64% porosity, 8.59% water sorption and 1.47% weight loss after 28 days with no cytotoxicity on the L929 cells. TA loaded nanofibers showed significantly less bleeding volume compared to the other groups, but no significant difference in bleeding time was seen with the blank nanofibers. In other words, the blank nanofibers alone had a hemostatic effect. TA loaded nanofibers were effective in bleeding control and hemorrhagic situations by reducing bleeding time and volume.     

Electrospun antibacterial nylon nanofibers through in situ synthesis of nanosilver: preparation and characteristics

A new method for production of nylon nanofibers with antibacterial properties containing silver nanoparticles (nylon nanofibers/Ag NPs) is introduced via in situ synthesis of nano-silver by reduction of silver nitrate in the polymer solution prior to electrospinning. The properties of the electrospinning solutions and the structures of the electrospun fibers were studied using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDAX), UV?Cvis spectrophotometer and reflection spectrophotometer. Further, the antibacterial properties of the nanofibers were investigated against Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive) bacteria. Interestingly, an antibacterial properties has been found on nylon 6 nanofibers while the nylon nanofibers/Ag NPs showed excellent antibacterial activities against both tested bacteria. The produced nylon nanofibers/Ag NPs can be a good candidate for biomedical applications, water and air filtration.     

Study on the mechanical and thermal properties of polylactic acid/hydroxyapatite@polydopamine composite nanofibers for tissue engineering

Electrospun nanofibers have attracted tremendous attention because of their similar structure with extracellular matrix. In this work, the polydopamine (PDA) coating layer was first applied to modify hydroxyapatite (HA) nanoparticles and obtain functional HA@PDA nanoparticles. Subsequently, the polylactic acid (PLA)/HA@PDA composite nanofibers were prepared via electrospinning. The hydrophilicity and water absorption of PLA/HA@PDA composite nanofibers were larger than those of PLA and PLA/HA composite nanofibers. The thermal stability, static and dynamic mechanical properties of PLA/HA@PDA composite nanofibers significantly increased because the PDA coating layer on the surface of the HA nanoparticles acted like a glue-like transition layer, which led to an increase in interfacial adhesion between HA@PDA nanoparticles and the PLA matrix. The attachment and viability of mouse embryonic osteoblast cells (MC3T3-E1) cultured on the PLA/HA@PDA composite nanofibers were significantly increased compared with those cultured on the PLA and PLA/HA composite nanofibers. These results suggested that the PLA/HA@PDA composite nanofibers have superior mechanical and biological properties, which makes it potentially useful for tissue engineering scaffolds.     

Preparation and characterization of poly(vinyl alcohol) nanofiber mats crosslinked with blocked isocyanate prepolymer

Poly(vinyl alcohol) (PVA) nanofibers crosslinked with blocked isocyanate prepolymer (BIP) were successfully prepared using the electrospinning process and subsequent thermal treatment. Fourier transform infrared spectroscopy and solid‐state ¹³C NMR spectroscopy demonstrated that chemical crosslinks between the hydroxyl group of PVA and the isocyanate group of BIP were formed. Thermogravimetric analysis and differential scanning calorimetry results indicated that when the BIP content was increased, the thermal stability of PVA/BIP nanofibers increased, and the crystallinity of PVA decreased. Field emission scanning electron microscopy was used to measure the average diameter (200–300 nm) of the electrospun PVA/BIP nanofibers. The water contact angles were 10.2° and 113° for the pristine PVA nanofibers and PVA nanofibers crosslinked with 8 wt% BIP, respectively. The tensile strength of the crosslinked PVA nanofibers was 53.7 MPa, which was seven times higher than that of pristine PVA. The improved tensile strength and water resistance of the crosslinked PVA/BIP nanofibers were due to a combination of increased crosslinking density and decrease in the number of hydroxyl groups on the surface of the PVA/BIP nanofibers. Copyright © 2010 Society of Chemical Industry     

Electrospun polyester/cyclodextrin nanofibers for entrapment of volatile organic compounds

Polyester (PET) nanofibers incorporating cyclodextrins (CD) were obtained via electrospinning. α‐CD, β‐CD, and γ‐CD were used to functionalize PET nanofibers. Bead‐free PET/CD nanofibers were obtained from lower polymer concentration indicating that the incorporation of CD in polymer solution improved the electrospinnability of the PET nanofibers. XRD studies indicated that CD were distributed into nanofiber without forming crystalline aggregates. FTIR peak shift was observed possibly due to interaction between CD and PET. TGA confirmed that initial CD loading (25%, w/w) in the polymer solution was preserved for the PET/CD nanofibers. The presence of most of CD on the surface of PET/CD nanofibers was confirmed by XPS analysis and contact angle measurement. DMA results indicated that incorporation of CD improved the mechanical property of the nanofibers. Our studies showed that PET/CD nanofibers can effectively entrap aniline vapor as a model volatile organic compound (VOC) from surrounding owing to their very large surface area and inclusion complexation capability of CD. The entrapment efficiency of aniline vapor was found to be better for PET/γ‐CD nanofibers compared to PET/α‐CD and PET/β‐CD nanofibers. Our findings suggested that electrospun PET nanofibers functionalized with CD may be used as filtering material for removal of VOC in air filtration. POLYM. ENG. SCI., 54:2970–2978, 2014. © 2014 Society of Plastics Engineers     

Environmentally friendly biological nanofibers based on waste feather keratin by electrospinning with citric acid vapor modification

Waste feather keratin (FK)-based nanofibers by electrospinning and citric acid (CA) vapor modification has been successfully prepared and investigated. FK, poly(vinyl alcohol), and poly(ethylene oxide) have been used as raw materials and CA vapor as cross-linker. The structural, thermal, hydrophobicity, and mechanical properties of FK-based nanofibers by CA vapor modification with various cross-linking time have been completely explored. In order to investigate the effect of H₂O vapor on CA vapor modification, H₂O vapor modification was performed on the FK-based nanofibers at the same conditions. The results show that the average diameter of nanofibers increased from 250.83 ± 29.65 nm to 338.79 ± 31.43 nm by CA vapor modification with 15 h. Similarly, the thermal stability and water resistance of FK-based nanofibers by CA vapor modification have been significantly improved. The tensile strength (σ_b) and elongation at breakage point (ε_b) of FK-based nanofibers after CA vapor modified for 15 h were about 1.5 and 2 times higher than that of nonmodified nanofibers, respectively. By comparison, scanning electron microscopy results suggest that the FK-based nanofibers modified by H₂O vapor cannot maintain the morphology of the nanofibers, resulting in large-scale adhesion. The thermal properties of FK-based nanofibers with H₂O vapor modification have no obvious change. The hydrophobicity and mechanical properties of FK-based nanofibers by H₂O vapor modification are not as good as that of CA vapor modification. In summary, these results exhibit that nontoxic and natural CA can be used as cross-linking agent to enhance the comprehensive performance of FK-based nanofibers. This study provides a new method to modify FK-based nanofibers and refined the waste feathers, which not only protected the environment, but also gained benefits, which has a broad application prospect.     

Fabrication and DOE Optimization of Electrospun Chitosan/Gelatin/PVA Nanofibers for Skin Tissue Engineering

Chitosan/gelatin-based nanofibers display excellent biological performance in tissue engineering because of their biocompatible composition and nanofibrous structure with a high surface-to-volume ratio mimicking the native extracellular matrix. In this study, to save time and cost of experiments, a response surface methodology based on Box–Behnken design (BBD) is developed to predict the mean diameter of (chitosan:gelatin)/poly(vinyl alcohol) (PVA) nanofibers in three volume ratios of chitosan:gelatin by considering PVA percentage, applied voltage, and flow rate as input variables. The morphology and chemical composition of nanofibers are investigated through scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR), respectively. The optimum conditions to yield the minimum diameter of nanofibers with chitosan:gelatin ratios of 25:75, 50:50, and 75:25 are found and result in 165, 121, and 92 nm, respectively, which show good accordance with BBD estimated results. The tensile testing indicates that nanofibers containing higher ratio of chitosan:gelatin result in higher tensile stress and lower toughness and tensile strain. The water contact angle analysis (WCA) shows the appropriate hydrophilicity of crosslinked nanofibers. The MTT assay shows excellent cell viability and cell attachment of nanofibers for mouse fibroblast (L929) cells. The results indicate that optimum nanofibers are potent candidates for wound healing applications.     

Preparation and characterization of antimicrobial electrospun poly(vinyl alcohol) nanofibers containing benzyl triethylammonium chloride

The aim of this study was to characterize antimicrobial electrospun poly(vinyl alcohol) (PVA) nanofibers containing benzyl triethylammonium chloride (BTEAC) as an antimicrobial agent. The antimicrobial BTEAC-PVA nanofibers were prepared through electrospinning at the optimal conditions of 15 kV voltage and a 1.0 mL h^− 1 flow rate. Based on the minimum inhibitory concentration (MIC) test results against Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli and Klebsiella pneumonia, BTEAC-PVA nanofibers containing 2.6% BTEAC were fabricated to test the antibacterial and antiviral activities. The average diameter of the BTEAC-PVA nanofibers increased from 175.7 to 464.7 nm with increasing BTEAC concentration from 0 to 2.6%. The antimicrobial activities of the BTEAC-PVA nanofibers were tested against bacteria. The antibacterial tests with 2.6% BTEAC-PVA nanofibers demonstrated that bacterial reduction in PVA nanofibers was similar to the control value, indicating that PVA had a minimal effect on bacteria death. For the BTEAC-PVA nanofibers, the bacterial reduction ratio increased with increasing contact time, demonstrating that BTEAC-PVA nanofibers successfully inhibited the growth of bacteria. In addition, the antiviral tests against viruses (bacteriophages MS2 and PhiX174) showed that the BTEAC-PVA nanofibers inactivated both MS2 and PhiX174.     

Electrospinning of polyacrylonitrile solutions containing diluted sodiumthiocyanate

The effect of NaSCN salt on the spinnability of polyacrylonitrile (PAN) solutions, its resulting morphology, mechanical property, and the flame resistance of the resulting electrospun nanofibers were studied. The intent was to develop a method to produce nanosized carbon fiber precursors with good properties. Electrospun PAN nanofibers from 9.7–9.9 wt% PAN/sodiumthiocyanate (NaSCN) (aq)/Dimethylformamide (DMF) solutions with 1.0–2.9 wt% NaSCN (aq), and 10–15 wt% PAN/DMF solutions without salt exhibited good spinnability and morphology with no beading in the range of applied voltage (18–20 kV) and take‐up velocity (9.8–12.3 m/s). The relatively high take‐up velocity produced good yarn alignment. The diameter distributions of the PAN nanofibers containing the NaSCN salt were narrower than those of the PAN/DMF nanofibers without the salt. It was determined that the maximum content of salt for production of electrospun PAN nanofibers with good morphology was below 3.8 wt% (40 wt% based on PAN). The salt concentration can positively influence on the narrow diameter distributions of the resulting electrospun fibers. Also, it could be confirmed that the salt effect on mechanical property and flame resistance of electrospun PAN nanofibers. In particular, the elongation of the PAN nanofiber with 2.9 wt% NaSCN (aq) was significantly increased as much as 186% compared with that of 10 wt% PAN nanofiber without the salt. The flame resistance and mechanical properties of the stabilized PAN nanofibers with NaSCN (aq) increased after oxidization process. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers.     

Hydrophilic non-wovens made of cross-linked fully-hydrolyzed poly(vinyl alcohol) electrospun nanofibers

Fully-hydrolyzed poly (vinyl alcohol) (PVA) nanofibers were successfully electrospun from aqueous solutions of PVA in the presence of acetic acid. A continuous spinning of uniform PVA nanofibers proceeded by the addition of acetic acid due to the changes of electronic conductivity and surface tension of aqueous solution of PVA. When cross-linking agent 1 was added to aqueous solution of PVA and subsequent thermal treatment of as-spun nanofibers, chemically cross-linked PVA nanofibers were achieved to resist disintegration in contact with hot water and the tensile mechanical property of nanofiber non-wovens was greatly improved by the formation of cross-linking points. Magnetite was deposited uniformly onto the hydrophilic surface of cross-linked PVA nanofibers and the resulted nanofibers decorated with magnetite showed a magnetic responsiveness. The deposition of magnetite on the PVA nanofibers can generate self-standing magnetic non-wovens.     

C2H2 gas sensor based on Ni-doped ZnO electrospun nanofibers

Pure and Ni-doped ZnO nanofibers were synthesized using the electrospinning method. The morphology, crystal structure and optical properties of the nanofibers were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and photoluminescence (PL) spectroscopy, respectively. It is found that Ni doping does not change the morphology and crystal structures of the nanofibers, and the ultraviolet emissions of ZnO nanofibers present red shift with increasing Ni doping concentration. C₂H₂ sensing properties of the sensors based on the nanofibers were investigated. The results show that the C₂H₂ sensing properties of ZnO nanofibers are effectively improved by Ni doping, and 5 at% Ni-doped ZnO nanofibers exhibit a maximum sensitivity to C₂H₂ gas.     

Fabrication and Thermal Dissipation Properties of Carbon Nanofibers Derived from Electrospun Poly(Amic Acid) Carboxylate Salt Nanofibers

Polyimides (PIs) possess excellent mechanical properties, thermal stability, and chemical resistance and can be converted to carbon materials by thermal carbonization. The preparation of carbon nanomaterials by carbonizing PI‐based nanomaterials, however, has been less studied. In this work, the fabrication of PI nanofibers is investigated using electrospinning and their transformation to carbon nanofibers. Poly(amic acid) carboxylate salts (PAASs) solutions are first electrospun to form PAAS nanofibers. After the imidization and carbonization processes, PI and carbon nanofibers can then be obtained, respectively. The Raman spectra reveal that the carbon nanofibers are partially graphitized by the carbonization process. The diameters of the PI nanofibers are observed to be smaller than those of the PAAS nanofibers because of the formation of the more densely packed structures after the imidization processes; the diameters of the carbon nanofibers remain similar to those of the PI nanofibers after the carbonization process. The thermal dissipation behaviors of the PI and carbon nanofibers are also examined. The infrared images indicate that the transfer rates of thermal energy for the carbon nanofibers are higher than those for the PI nanofibers, due to the better thermal conductivity of carbon caused by the covalent sp² bonding between carbon atoms.