Electrospun polyindole nanofibers as a nano-adsorbent for heavy metal ions adsorption for wastewater treatment

Polyindole nanofibers were prepared via electrospinning method using acetonitrile as solvent. The obtained electrospun polyindole nanofibers were characterized with SEM, TEM, FTIR and BET surface areas measurements. Adsorption experiments were carried out in batch sorption mode to investigate the effect of pH, contact time and diameter of polyindole nanofibers. The Cu(II) adsorption was highly pH dependent and the optimum pH was found to be 6. The maximum adsorption capacities for electrospun polyindole nanofibers and polyindole powders were 121.95 and 18.93 mg/g attained in 15 and 60 min, respectively. With the diameter of polyindole nanofibers increasing, the adsorption capacity slightly decreased. The adsorption isotherm data fitted well to the Langmuir isothermal model which indicates that the monolayer adsorption occurred. The kinetics data analysis showed that the adsorption process could be described by pseudo-second order kinetic model, suggesting a chemisorption process as the rate limiting step. Thermodynamic parameters ΔHº, ΔSº and ΔGº for the Cu(II) adsorption by polyindole nanofibers were calculated. The results showed that the Cu(II) adsorption was feasible, spontaneous and endothermic. Desorption results revealed that the adsorption capacity can remain up to 75 % after 10 times usage. The electrospun polyindole nanofibers would have promising application for removal of Cu(II) from wastewater treatment.     

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.     

Facile fabrication of PVAc-g-PVDF coating on surface modified cotton fabric for applications in oil/water separation and heavy metal ions removal

Selective separation is an effective method for the removal of heavy metal ions and waste oil from wastewater. Polyvinylidene fluoride (PVDF) was functionalized with polyvinyl acetate (PVAc) by in-situ polymerization, and novel PVAc-g-PVDF coating on surface modified cotton fabric were prepared. The contact angle (CA), pure water flux (PWF) and self-cleaning ability of coated cotton fabric were investigated in detail. In addition, the separation performance of coated cotton fabric was reflected by the removal of heavy metal ions in simulated wastewater. The results revealed that the PVAc-g-PVDF-coated cotton fabric was free of waste oil adhesion and was self-cleaning from waste oil in aqueous environment. Meanwhile, this coated cotton fabric can effectively separate oil/water mixtures with a high flux and high oil rejection, and was easily recycled for long-term use. More importantly, the heavy metal ions rejection ratio and adsorption capacity of cotton fabric were also improved with the addition of PVAc-g-PVDF coating. PVAc-g-PVDF-coated cotton fabric exhibited excellent rejection stability and reuse performances after several times fouling and washing tests. It can be expected that the present work will provide insight into a scaled-up fabrication process of PVAc-g-PVDF coating for purifying wastewater.     

Highly stable coated polyvinylpyrrolidone nanofibers prepared using modified coaxial electrospinning

Hydrophobic polyvinylpyrrolidone (PVP) nanofibers, which is intensely hygroscopic, has been successfully prepared to improve their moisture resistance using a modified coaxial electrospinning process. A stearic acid (SA) solution was exploited as the sheath fluid to coat the fibers. Scanning electron microscopy demonstrated that the SA-coated PVP nanofibers became increasingly small with a rise in the sheath-to-core flow rate ratio; continuing to increase the sheath flow rate beyond a cut-off point resulted in nanofibres with very complicated morphologies. Transmission electron microscope images showed that SA formed a thin layer on the PVP nanofibers, with SA nanoparticles present on the fiber surfaces when a sheath-to-core flow rate ratio of 0.2:0.8 was used. Attenuated total reflectance-Fourier transform infrared spectroscopy verified the coating of SA onto the PVP nanofibers, and also the formation of hydrogen bonds between the SA and PVP molecules. The SA-coated PVP nanofibers were found to have much enhanced moisture resistance over pure PVP fibers. Modified coaxial electrospinning hence comprises a novel and powerful strategy for nanocoating and surface modification of polymer nanofibers.     

A novel method for manufacturing nanofibers

This study presents a method for the fabrication of ultrafine polymeric nanobers utilizing centrifugal and electrostatic forces simultaneously. To reduce the diameter and variability of nanofibers produced from polyacrylonitrile (PAN) and poly-L-lactic acid (PLLA), a unique electro-centrifuge spinning device was designed using rotating nozzle and collector, whereas the fabrication process (spinning head) was skillfully sealed from ambient airflow. The polymer solution was continuously delivered by a rotating nozzle and the nanofibers were collected by a rotating cylindrical collector at the same rotational speed as the nozzle. Field emission scanning electron microscope (FESEM) results demonstrated that this method has a significant effect on the quality and fineness of nanofibers. The diameters of nanobers were controlled by adjusting the rotation speed of spinning head. The effect of the rotation speed on the morphology of the nanofibers fabricated by this device was also evaluated. In order to provide a useful context for the current nanofiber production method, nanofibers obtained in this method were compared with those produced by other methods. The results show that air-sealedcentrifuge-electrospinning system (ASCES) is a facile method for the fabrication nanobers with smaller diameters and high uniform structures.     

Bipolar membrane modified by cation/anion exchange nanofibers containing copper phthalocyanine derivatives with different substituents

Carboxymethyl cellulose (CMC)-polyvinyl alcohol (PVA) and chitosan (CS)-polyvinyl alcohol were cross-linked by Fe³⁺ and glutaraldehyde respectively to prepare the cation exchange membrane layer and the anion exchange membrane layer, polyvinyl alcohol-sodium alginate (SA)-copper phthalocyanine tetrasulfonic acid (CuTsPc, or copper tetracarboxy phthalocyanine: CuTcPc) cation exchange nanofibers or polyvinyl alcohol-chitosan-copper tetraaminophthalocyanine (CuTAPc) anion exchange nanofibers prepared by electrospinning technique were introduced into the interlayer to obtain the modified bipolar membrane (BPM). The experimental results showed that in comparison with the BPM without the cation/anion exchange nanofibers interlayer, the water splitting efficiency of the modified BPM was obviously increased, and its membrane impedance decreased. When the concentration of CuTsPc in the PVA-SA-CuTsPc nanofibers was 3.0 %, the transmembrane voltage drop (IR drop) of the CMC-PVA/PVA-SA-CuTsPc/CS-PVA BPM was as low as 0.5 V at a high current density of 90 mA·cm^?2.     

Polycarbazole modified carbon fiber microelectrode: Surface characterization and dopamine sensor

Electropolymerization of carbazole (Cz) by cyclic voltammetry (CV) onto carbon fiber microelectrodes (CFME) (diameter ∼7 μm) in dichloromethane (CH₂Cl₂) solution of 0.1 mol·dm⁻³ tetraethyl ammonium perchlorate (TEAP) results in the formation of polycarbazole (PCz) thin film coatings. CV results showed that these PCz thin films have reversible redox behavior in monomer-free electrolyte solution. The resulting thin polymer films were characterized using Fourier transform infrared attenuated total reflectance spectroscopy (FTIR-ATR) and atomic force microscopy (AFM). Results performed at optimum experimental conditions indicate that electrodes show a reversible and stable behavior over sixty eight days of testing for dopamine in 100 μmol·dm⁻³ buffer solution. A detection limit for PCz thin films as low as 0.1 μM (3S/N) was obtained for the polycarbazole (PCz) thin films formed using CV. Hence, this novel sensor can be considered as promising sensor for dopamine detection.     

Influence of alkaline metal ions on flame retardancy and thermal degradation of cellulose fibers

Cellulose-Na and cellulose-K fibers are obtained by alkalization and etherification of viscose fiber. Flame retardancy and thermal degradation of cellulose-Na and cellulose-K fibers are investigated using limiting oxygen index (LOI), cone calorimetry (CONE), thermal gravimetry (TG), and differential TG (DTG). The LOI values of cellulose-Na and cellulose-K fibers are 33 and 30, compared with about 20 for viscose fiber. In CONE studies, cellulose-Na and cellulose-K fibers show much lower heat release rates, total heat release and effective heats of combustion than viscose fiber does. In addition, TG and DTG studies reveal that the second initial degradation temperature, the temperature of maximum degradation rate and the maximum degradation rate for cellulose-Na and cellulose-K fibers are much lower than those of viscose fiber. Cellulose-Na and cellulose-K fibers generate much more residue or carbonaceous char than viscose fiber does. Scanning electron microscopy studies of combustion residues after LOI testing indicate that cellulose-Na and cellulose-K fibers produce massive, thick residue crusts.     

Electrospun nanofibers of poly(NPEMA-co.-CMPMA): Used as Heavy metal ion remover and water sanitizer

Homo and copolymers of monomers 2-(N-phthalimido) ethylmethacrylate (NPEMA) and 4-Chloro-3-methyl phenyl methacrylate (CMPMA) were prepared in N,N-dimethyl formamide (DMF) solution at 70 °C using 2,2-azobisisobutyronitrile (AIBN) as initiator. The solution of poly(NPEMA-co.-CMPMA) in 20 % DMF was used to fabrication electrospun nanofiber by electrospinning technique. IR data were primarily employed to characterize polymers. The formation of nanofibers was identified by SEM study. The metal ion uptake capacity of copolymers and nanofibers were obtain by batch equilibrium method using different metal ion solution. The antimicrobial activity of the copolymers, Polymer nanocomposites and their nanofibers were tested against different microbial organisms by using quantitative method. The main objective of this investigation was to find whether nanofiber are better remover of metal ions compared to copolymers. It was also aimed to study the efficacy of nanofibers of copolymers and copolymer composite with nano Ag as water sanitizer.     

Colorimetric detection of transition metal ions with azopyridine-based probing molecule in aqueous solution and in PMMA film

We report on an azopyridine derivative for probing transition metal ions and fabrication of its films. The probe, AP, showed a sensitive absorption change toward transition metal ions, especially cobalt ion, even at the concentration of ppm range, accompanied by yellow-to-red color transition with noticeable isosbestic point. In addition, the AP-containing PMMA film with high transparency can be fabricated by spin-casting without any aggregation of AP. The film with PMMA matrix shows good sensitivity toward cobalt ion similar to the case in the solution with a feature of metallochromic transition.     

RSM and ANN approaches for modeling and optimizing of electrospun polyurethane nanofibers morphology

This paper focused on using response surface methodology (RSM) and artificial neural network (ANN) to analyze polyurethane (PU) nanofibers morphology synthesized by electrospinning. The process was characterized in detail by using experimental design to determine the parameters that may affect the nanofibers morphology such as polymer concentration, a tip to collector distance and applied voltage. It was concluded that solution concentration plays an important role (relative importance of 79.85 %) against nanofibers diameter and its standard deviation. Based on the results, applied voltage has a different effect on the nanofiber diameter at low and high solution concentrations. Moreover, the tip to collector distance parameter has no significant impact on the average nanofiber diameter. The finest PU nanofiber (201 nm) was obtained from experimental under conditions of: 9 w/v% polymer concentrations, 12 cm tip to collector distance and 16 kV applied voltage. The results show a very good agreement between the experimental and modeled data. It was demonstrated that both models (specially, in case of neural network) are excellent for predicting diameter of PU nanofibers. Furthermore, numerical optimization has been performed by considering desirability function to access the region in design space that introduces minimum average diameter.     

Manufacturing polymethyl methacrylate nanofibers as a support for enzyme immobilization

Nanofibers have a great potential for enzyme immobilization application due to their large surface area to volume ratio besides their porous structure. In this work, we produce polymethyl methacrylate (PMMA) nanofibers via electrospinning method in dimethylformamide (DMF) as solvent. Thereafter, we employ a chemical method on final PMMA nanofiberous web to covalently immobilize acetylcholinesterase (AChE) enzyme on membrane surface. Morphology and tensile properties of nanofibers are studied as first steps of characterization to make sure of obtaining a properly stable membrane for enzyme carrying application. Thereafter, the stability and activity of immobilized enzymes as two main characteristic parameters are tested and reported for different applications such as biosensor manufacturing.     

A highly selective rhodamine based color turn on and fluorescence turn off sensor toward late IB metal ions

A fluorescence “turn-off” and color “turn-on” probe for late IB metal ions (Fe³⁺/Co²⁺/Ni²⁺/Cu²⁺/Zn²⁺) was developed based on rhodamine B. The probe was synthesized by condensation between rhodamine B and 8-hydroxyjulolidine-9-carboxaldehyde, which provided excellent selectivity function for late IB metal ions detection. It binds Cu²⁺ in a 1:1 stoichiometry in acetonitrile solution. This probe displays distinct color and fluorescence change upon the addition of late IB metal ions and little interference with other biologically relevant metal ions. Limit of detection for Cu²⁺, Fe³⁺, and Co²⁺ is higher than that of Zn²⁺ and Ni²⁺. In addition, the limit of detection toward Cu²⁺ is about 312 times lower than the World Health Organization (WHO) recommended level in drinking water.     

Electrospun titanium dioxide nanofibers: Fabrication,properties and its application in photo-oxidative degradation of methyl orange (MO)

In this study, we synthesed two kind of TiO₂ nanomaterial (nanoparticles and nanofiber) for photocatalitic degradation of methyl orange (MO) as pollutant. TiO₂ nanoparticles were synthesized by sol-gel technique using titanium (IV) isopropoxide as precursor. Polyvinyl acetate (PVAc)/TiO₂ hybrid nanofibers were fabricated by combining sol-gel process with electrospinning technology, which consisted of PVAc as organic segment and TiO₂ as inorganic part. Crystalline phase of TiO₂ nanomaterials was investigated by X-ray diffraction (XRD). The XRD results show that the TiO₂ nanomaterials crystallize in anatase with some rutile phase and these consist of titanium dioxide nano-crystals. The surface structures of TiO₂ nanomaterials were examined using scanning electron microscopy (SEM). SEM scanning revealed that the nanoparticle and nanofibrous structure was formed. Fourier transform infrared spectroscopy (FTIR) was employed to analyze the chemical structures of the PVAc/TiO₂ hybrid nanofibers. The FTIR analysis indicated the newly formed associated hydrogen bond because of the hybrid effect between PVAc and TiO₂ sol. Finally, The photooxidative decomposition of methylene blue by using the titania nanomaterials was examined and compared.     

Preparation of amidoxime-modified polyacrylonitrile nanofibers immobilized with laccase for dye degradation

A novel approach to preparing multifunctional composite nanofibrous membrane was developed. Polyacrylonitrile (PAN) nanofibrous membrane was fabricated by electrospinning and then the nitrile groups in PAN copolymer was chemically modified to obtain amidoxime modified PAN (AOPAN) nanofiber membrane which was further used as a functional support for laccase immobilization. During the process of reactive dye degradation catalyzed by the AOPAN nanofiber membrane immobilized with laccase, metal ion adsorption occurred at the same time. The chemical modification was confirmed by Fourier transform spectroscopy (FTIR). Scanning electron microscope (SEM) was employed to investigate the surface morphologies of the electrospun nanofibers before and after laccase immobilization. The effects of environmental factors on laccase activity were studied in detail. It was found that the optimum pH and temperature for the activity of immobilized laccase was 3.5 and 50 °C. The relative activity retention of the immobilized laccase decreased dramatically during the initial four repeated uses. After 20 days’ storage, the activity retention of immobilized laccase was still high above 60 %. It has also proved that laccase immobilized on AOPAN nanofiber membrane performed well in dye degradation and metal ion adsorption.     

基因组DNA快速提取及在转基因大豆检测中的应用

基因组DNA的提取是DNA分子水平研究和检测的重要环节.为补充完善现场检测方法,根据硅膜吸附DNA的特性,结合过滤膜和注射器,开发一种现场快速提取植物基因组DNA的方法.选取大豆、棉花、油菜、玉米、水稻5种主要作物的叶片和种子为样品提取DNA,利用PCR和普通重组酶聚合酶扩增(recombinase polymeras...     

Fabrication of electrospun Poly L-lactide and Curcumin loaded Poly L-lactide nanofibers for drug delivery

The present work reports the preparation of Poly L-Lactide (PLLA) and Curcumin loaded Poly L-Lactide (CPLLA) nanofibers by electrospinning. A series of PLLA solution (12 wt %) and C-PLLA (12 wt % PLLA) solution containing Curcumin (0.5 wt % and 1 wt %)) were electrospun into nanofibers. SEM images showed the average diameter of PLLA and C-PLLA in the range of 50?C200 nm. The TEM images showed the dispersion of Curcumin on C-PLLA nanofibers. The XRD pattern indicated decreases of crystallinity with the increase in the amount of Curcumin. The characteristic peak of Curcumin was confirmed by FTIR. The TGA results showed the degradation of PLLA and C-PLLA close to 300 °C. The percentage porosity and the contact angle of PLLA were found to be 90.2 % and 115±3 ° with deionised water, respectively. The water uptake percentage was found to be 17.6 %. The percentage cumulative release of Curcumin at the end of 8th day for 0.5 and 1.0 wt % formulations was 81.4±1.3 and 86.7±1.7 % respectively. The in-vitro biological cytotoxicity studies were performed using C6 glioma cells and NIH 3T3 fibroblast by MTT assay and SEM analysis.     

Fluorosilicone modified polyacrylate emulsifier-free latex: Synthesis,properties, and application in fabric finishing

Fluorosilicone modified polyacrylate emulsion was successfully synthesized via emulsifier-free emulsion polymerization using polymerizable surfactant and sol-gel process. TEM analysis indicated that the hybrid particles were spherical-like particles with narrow size distributions. The influence of synthetic conditions on the physical and chemical properties of fluorosilicone modified polyacrylate was investigated, including the mass ratio of methyl methacrylate (MMA)/butyl acrylate (BA) and the content of dodecafluoroheptyl methacrylate (DFMA) and ethyl silicate (TEOS). The water absorption decreased as the MMA/BA mass ratio was reduced from 5/4 to 2/4, then increased afterwards. With the reducing of MMA/BA mass ratio, the tensile strength decreased, while the elongation at break increased. The thermal stability of the hybrid film was improved with the increasing of TEOS amount. Finally, the contact angle results showed that the finished fabric had the excellent water repellency. Meanwhile, the SEM measurements confirmed that the finished fabric had the rough surface. XPS analysis demonstrated that there was a layer of fluorosilicone modified polyacrylate film covered on the finished fabric surface, and fluorinated segments had the tendency to be enriched at the film-air interface.     

Preparation and characterization of nylon-6/gelatin composite nanofibers via electrospinning for biomedical applications

Easy fabrication, porosity, good mechanical properties, and composition controllable of the electrospun nanofiber mat make this material a promising candidate for wound dressing applications. In the present study, nylon6/gelatin electrospun nanofiber mats are introduced as novel wound dressing materials. The introduced mats were synthesized by electrospinning of nylon6 and gelatin mixtures, three mats containing different gelatin content were prepared; 10, 20 and 30 wt%. Interestingly, addition of the gelatin did not affect the mechanical properties of the nylon 6, moreover the mat containing 10 wt% gelatin revealed higher mechanical properties due to formation of spider-net like structure from very thin nanofibers (～10 nm diameter) bonding the main nanofibers. Biologically study indicates that gelatin incorporation strongly enhances the bioactivity performance as increasing the gelatin content linearly increases the MC3T3-E1 cell attachment. Overall, the obtained results recommend exploiting the introduced mats as wound dressing material.     

Conjugating S-nitrosothiols with fluorescent nanofibers for the controlled release and real-time detection of nitric oxide

In this work, a novel hybrid fibrous vehicle was developed for the release and real-time detection of nitric oxide (NO). The vehicle consisted of poly(L-lactide)/chitosan (PLLACS), cadmium tellurium quantum dots (CdTe QDs), and conjugating S-nitrosothiols. CdTe QDs were placed on the surface of PLLACS fibers as NO fluorescent probes through coaxial electrospinning; in this method, the PLLACS was used as filament material. Water-dispersible CdTe QDs were synthesized using mercaptoacetic acid as a stabilizer. The amino groups of chitosan served as reactive sites where chitosanbased S-nitrosothiols were formed. The fibrous PLLACS-QDs-NO composite was found to release NO under UV. The released NO could be detected in real time on the basis of the fluorescence quenching mechanism of QDs. These PLLACSQDs-NO nanofibers provide insights into novel designs of biocompatible NO delivery systems.