Enhanced simulated solar sono-photocatalytic performance and antibacterial activities of ZnO/NiO heterojunction nanofibrous membranes

ZnO/NiO heterojunction nanofibrous membranes with different Zn/Ni molar ratios were successfully prepared via electrospinning. The microstructures of the nanofibers were characterized by using scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. The ZnO/NiO heterojunction nanofibrous membranes showed superior photocatalytic performance on Congo red, particularly under ultrasonic action and simulated solar irradiation. The degradation of Congo red could reach 100% after 40 min with a high degradation constant of 0.064 min^?1. Additionally, the catalyst maintained high photocatalytic activity over five cycles. Furthermore, the heterojunction nanofibrous membranes had good antibacterial effects on Escherichia coli and Staphylococcus aureus with an inhibition zone width of above 8 mm. The generation of superoxide free radical and hydroxyl free radicals played important roles for the heterojunction nanofibrous membranes. This work is significant for studying the potential applications of nanofibers in waste water remediation.     

Holistic insights on polyimide nanocomposite nanofiber

ABSTRACT

Polyimides form an important class of high-performance polymers. Polyamides with aromatic macromolecular architecture have revealed excellent conducting, mechanical, and thermal properties for aerospace, automotive, electronics, and other technical industries. Recently, polyimide nanofiber and polyimide nanocomposite nanofiber have been focused for fabrication, essential physical features, and subsequent performance. Due to diversity of dianhydrides, diamines, and reinforced nanoparticles, various polyimide nanocomposite nanofibers have been judiciously designed. This comprehensive review highlights indispensable perspectives of polyimide nanocomposite nanofiber particularly polyimide/graphene, polyimide/carbon nanotube, and polyimide/inorganic nanoparticle-based nanofibers. It is envisioned that nanocomposite nanofibers have various high-value applications such as membranes, battery separators, electrodes, etc.     

Thiol-modified cellulose nanofibrous composite membranes for chromium (VI) and lead (II) adsorption

Oxidized cellulose nanofibers (CNF), embedded in an electrospun polyacrylonitrile (PAN) nanofibrous scaffold, were grafted with cysteine to increase the adsorption capability for chromium (VI) and lead (II). Thiol-modified cellulose nanofibers (m-CNF) were characterized by titration, FT-IR, energy dispersive spectroscopy (EDS) and SEM techniques. Static and dynamic Cr(VI) and Pb(II) adsorption studies of m-CNF nanofibrous composite membranes were carried out as a function of pH and of contact time. The results indicated these membranes exhibited high adsorption capacities for both Cr(VI) (87.5 mg/g) and Pb(II) (137.7 mg/g) due to the large surface area and high concentration of thiol groups (0.9 mmol of –SH/gram m-CNF). The morphology and property of m-CNF nanofibrous composite membranes was found to be stable, and they could be used and regenerated multiple times with high recovery efficiency.     

Fabrication and Piezoelectric Property of BaTiO3 Nanofibers

BaTiO₃ (BTO) nanofibers were fabricated by sol–gel combined with electrospinning method. The effects of the concentration of acetic acid and sintering temperatures on the crystal phase and microstructure of the samples were investigated by scanning electron microscopy, X‐ray diffraction, and transmission electron microscopy (TEM). BTO nanofibers with improved surface morphology were obtained as the ethanol to acetic acid ratio (E/A) was 8:3. The fibers calcined at 750°C for 2 h exhibited good morphology and crystallization. TEM studies revealed that the BTO nanofibers were polycrystalline, with diameters being on the order of hundreds nanometer, where the existence of domains offered proof of ferroelectric structure. The ferroelectric domains and piezoresponse of BTO nanofibers were characterized by piezoresponse force microscopy. The calculated d₃₃ was 20 pm/V at maximum strain amplitude.     

Nano/micro-structured poly(ϵ-caprolactone)/gelatin nanofibers with biomimetically-grown hydroxyapatite spherules: High protein adsorption,controlled protein delivery and sustained bioactive ions release designed as a multifunctional bone regenerative membrane

Bioactive and biodegradable fibrous membranes are highly attractive for periodontal bone regeneration. Herein, we demonstrate a new approach for fabrication of a novel nano/micro-structured fibrous membrane made of biodegradable poly(?-caprolactone)/gelatin (PCL/GEL) nanofibers and biomemtically-grown hydroxyapatite spherules (HAs). The proposed approach includes electrospinning fabrication of PCL/GEL nanofibers containing nanobioglass (NBG) agglomerates and their biomimetic transformation into HAs. The NBG agglomerates (~1.9 μm in diameter) enabled the growth of biomimetic HAs (~4 μm in diameter) around the PCL/GEL nanofibers and generated a unique nano/micro-structure. Interestingly, the biomimetically-grown HAs imparted the PCL/GEL-HAs nanofibrous membrane with several remarkable properties including nano/micro-topography, bone-mimetic composition (Ca/P = 1.60), large specific surface area (~31 m²/g), high protein adsorption capacity (~157 μg protein/mg membrane) and controlled protein delivery with zero-order release kinetics; along with sustained release of therapeutic ions (Ca²⁺ ~ 37 ppm, PO₄^3? ~ 24 ppm, and SiO₄^4? ~ 61 ppm). Furthermore, the PCL/GEL-HAs membrane exhibited enhanced wettability, good biodegradability and adequate mechanical properties. Collectively, the PCL/GEL-HAs demonstrated unique properties and it can be considered as a novel multifunctional bioactive/biodegradable membrane for periodontal bone regeneration.     

High strength antibacterial membranes consisted of nanofibrous chitosan immobilized silver nanoparticles

Chitosan (CS) has biocompatibility and biodegradability, but the bulk CS hydrogel/membranes with its poor strength and limited antibacterial property could not satisfy the practical application. Here green dissolving/regeneration and in situ reduction strategy was combined to construct high strength antibacterial CS membranes. First nanofibrous CS hydrogels were constructed through dissolving CS in LiOH/KOH/urea aqueous system via freezing–thawing process followed regeneration. Then, Ag NPs were immobilized along CS nanofibers through in situ reductions of Ag + by the NH₂ group of CS. The obtained NCM-Ag composite dry membranes are easy for storing and can quick switch to nanofibrous hydrogels as absorbing water. Size of Ag NPs can be controlled to very small until 2 nm by concentration and limited space network. Fourier transform infrared spectroscopy and X-ray photoelectron spectrometer indicated the forceful grasp ability of CS nanofibers to Ag NPs for a stable binding, mechanical property was enhanced over 100Mpa as the nanofibrous structure and chain linked by Ag coordination. The NCM-Ag membranes had excellent antibacterial activities against both Staphylococcus aureus and Escherichia coli. Moreover, such nanofibrous CS membrane exhibited good adhesive ability to tissues. Combining all these properties, NCM-Ag membranes would be potential as antibacterial adhesion barrier to accelerate wound healing.     

Preparation of electrospun magnetic polyvinyl butyral/Fe2O3 nanofibrous membranes for effective removal of iron ions from groundwater

Removing iron ions from groundwater to purify, it is a challenge faced by countries across the globe, which is why developing polymeric microfiltration membranes has garnered much attention. The authors of this study set out to develop nanofibrous membranes by embedding magnetic Fe₂O₃ nanoparticles (MNPs) into polyvinylbutyral (PVB) nanofibers via the electrospinning process. Investigation was made into the effects of the concentration of the PVB and MNPs on the morphology of the nanofibers, their magnetic properties, and capacity for filtration to remove iron ions. The fabrication and presence of well-incorporated MNPs in the PVB nanofibers were confirmed by scanning electron microscopy and transmission electron microscopy. Depending on the concentration of the MNPs, the membranes exhibited magnetization to the extent of 45.5 emu g⁻¹; hence, they exceeded the performance of related nanofibrous membranes in the literature. The magnetic membranes possessed significantly higher efficiency for filtration compared to their nonmagnetic analogues, revealing their potential for groundwater treatment applications.     

Mechanically improved superhydrophobic nanofibrous polystyrene/high-impact polystyrene membranes for promising membrane distillation application

Robust membranes for commercial applications of membrane distillation (MD) are nearly the Achilles ankle of the process. Despite from high hydrophobicity requirements of the MD membranes, they must have enough mechanical and thermal stabilities. In this regard, flexible, superhydrophobic, and high-productive nanofibrous membranes were fabricated using mixed dope solutions made of polystyrene (PS) and high-impact PS (HIPS) through the electroblowing process. Although the PS nanofibers can be designed to have hierarchically rough surfaces to show superhydrophobicity, the inherent brittleness of this polymer still remains a big issue for practical application for a longer period of time. Upon adding HIPS into the PS-containing dope solution, the rigid PS membrane turned into a more flexible one with improved elongation at break from 5.83% to 14.89%. Also, excellent direct contact membrane distillation performance was achieved using high saline (up to 150 g/L) and 0.1 mM sodium dodecyl sulfate/35 g/L NaCl feed solutions during 96 and 24 h, respectively. Superhydrophobicity (˃160°) and high LEP value (up to 173.2 kPa) gifted membranes with outstanding wetting resistance. Our proposed procedure can pave the route for the facile fabrication of robust MD membranes using cost-effective materials and a high-throughput fabrication process.     

Polyvinyl alcohol-collagen-hydroxyapatite biocomposite nanofibrous scaffold: Mimicking the key features of natural bone at the nanoscale level

Polyvinyl alcohol (PVA) nanofibers, PVA/Type I Collagen (Col) and their composites with hydroxyapatite nanoparticles (nano-HAp) were prepared by electrospinning techniques. The composite nanofibrous membranes were subjected to detailed analysis. Morphological investigations show that the generated nanofibers (NFs) have uniform morphology with an average diameter of ∼160 nm for pure PVA, ∼176 nm for PVA/n-HAp, ∼245 nm for PVA/Col and ∼320 nm for PVA/Col/n-HAp. It is of interest to observe that large numbers of HAp nanorods are preferentially oriented parallel to the longitudinal direction of the electrospun PVA and/or PVA/Col NFs. FTIR and thermal analysis demonstrated that there was strong intermolecular hydrogen bonding between the molecules of PVA/Col/n-HAp. Furthermore, the obtained PVA/Col/nHAp NFs scaffold (7 cm × 11 cm) has a porous structure with adjustable pore size and shape. The pore size is in the range of 650 μm with a porosity of 49.5%. On the other hand, mechanical characterizations revealed that the incorporating of 5 wt% n-HAp into the matrix of PVA/Col nanofibers could significantly improve the rigidity of the resultant biocomposite nanofibrous scaffold. These results strongly suggest a huge potential of the prepared scaffold for bone tissue engineering.     

Construction of CuS/ZnO Z-scheme heterojunction as highly efficient piezocatalyst for degradation of organic pollutant and promoting N2 fixation properties

Piezocatalytic technology has great potential in addressing water-system pollution and countering energy crises issues. Herein, high-performance CuS/ZnO Z-scheme heterojunction piezocatalyst was prepared by environmentally friendly solid-state chemistry approach and explored piezocatalytic performances toward degradation of organic methylene blue (MB) dye pollutant and nitrogen (N₂) fixation activity under ultrasonic vibration. The CuS/ZnO piezocatalyst presents outstanding property in MB degradation process with high efficiency (94.7% in 40 min), high rate constant (0.06804 min⁻¹) and good recyclability stability in comparison with the numerous ZnO-based piezocatalysts. In addition, this catalyst also exhibits superior piezocatalytic activity with a production rate of nitrogen fixation rate of 77.5 μmol L⁻¹ g_cat⁻¹ h⁻¹ in the reduction of N₂ to ammonia process, which is approximately 4-folds higher than that of pristine ZnO. Such improvement was mainly attributed to the facilitating charge carriers separation via rational construction of Z-scheme heterojunction as well as enhanced redox capacity. A novel piezocatalytic Z-scheme heterojunction mechanism of CuS/ZnO has been proposed and elucidated. This work suggests that designing highly efficient CuS/ZnO piezocatalyst will be a promising candidate material for prospects application in coping with the environmental remediation pollutants and energy crisis problems.     

Electrospun nylon 6,6 nanofibers functionalized with cyclodextrins for removal of toluene vapor

Functional nylon 6,6 nanofibers incorporating cyclodextrins (CD) were developed via electrospinning. Enhanced thermal stability of the nylon 6,6/CD nanofibers was observed due to interaction between CD and nylon 6,6. X‐ray photoelectron spectroscopy and attenuated total reflectance Fourier transform infrared spectroscopy studies indicated the existence of some CD molecules on the surface of the nanofibers. Electrospun nylon 6,6 nanofibers without having CD were ineffective for entrapment of toluene vapor from the environment, whereas nylon 6,6/CD nanofibrous membranes can effectively entrap toluene vapor from the surrounding by taking advantage of the high surface‐volume ratio of nanofibers with the added advantage of inclusion complexation capability of CD presenting on the nanofiber surface. The modeling studies for formation of inclusion complex between CD and toluene were also performed by using ab initio techniques. Our results suggest that nylon 6,6/CD nanofibrous membranes may have potential to be used as air filters for the removal of organic vapor waste from surroundings. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41941.     

Nanofibrous alumina structures fabricated using high-yield alternating current electrospinning

Nanofibrous alumina (Al₂O₃) structures were fabricated from the precursor aluminum nitrate/polyvinylpyrrolidone (PVP) nanofibers prepared using a free-surface alternating current (AC) electrospinning method. Precursor nanofibers were generated at rates up to 6.4 g/h and collected as 100–300 µm thick sheets suitable for direct conversion into the nanofibrous alumina structures. The effects of process conditions and annealing temperature on the nanofiber diameter, morphology, shrinking behavior and crystalline phase formation were investigated by Scanning Electron Microscopy (SEM), Fourier Transform Infrared (FTIR) spectroscopy, and X-ray diffraction (XRD). Textural properties of Al₂O₃ fibrous sheets composed of micro-/meso-porous nanocrystalline γ-alumina nanofibers with 260±90 nm diameters after the calcination at temperatures in the range from 700 °C to 1000 °C were determined from N₂ adsorption/desorption isotherms. Preliminary air permeability and apparent air flow resistance studies of single sheet and multilayer nanofibrous alumina membranes were performed and compared with other porous alumina membrane structures for the evaluation of their possible usage in gas filtration, separation, and other applications.     

Preparation of dual mode encoding photochromic electrospun glass nanofibers for anticounterfeiting applications

Photochromism has shown to be a promising tool for improving the authenticity of commercially available products. Additionally, improving the engineering process of authentication patterns has been crucial to offer mechanically reliable anticounterfeiting nanofibers. Herein, the electrospinning technology was applied to develop mechanically reliable and photoluminescent silicon dioxide-based electrospun glass nanofibers (80–110 nm) embedded with lanthanide-activated aluminate (LA) nanoparticles (NPs; 1–2 nm) for anticounterfeiting purposes. The produced nanocomposite films exhibited photochromism from colorless in visible spectrum to green under ultraviolet irradiation. The nanofibrous film transparency was maintained by presenting the strontium aluminate pigment as nano-scaled particles, which improves its distribution and prevents the formation of aggregates in the electrospun glass nanofibrous bulk. After being excited at 365 nm, the nanofibers made of phosphor@glass (LANPs@GLS) displayed an emission band at 519 nm. Increases in the pigment ratio enhanced the hydrophobicity of the LANPs@GLS nanofibers without altering their intrinsic characteristics. The LANPs@GLS films exhibited fast and reversible photochromism without fatigue when activated by UV light. Transparency and flexibility were shown by the nanofibrous mats. The proposed technique is reliable for making a wide range of anticounterfeiting materials.     

Fabrication of Chitosan/Silk Fibroin Composite Nanofibers for Wound-dressing Applications

Chitosan, a naturally occurring polysaccharide with abundant resources, has been extensively exploited for various biomedical applications, typically as wound dressings owing to its unique biocompatibility, good biodegradability and excellent antibacterial properties. In this work, composite nanofibrous membranes of chitosan (CS) and silk fibroin (SF) were successfully fabricated by electrospinning. The morphology of electrospun blend nanofibers was observed by scanning electron microscopy (SEM) and the fiber diameters decreased with the increasing percentage of chitosan. Further, the mechanical test illustrated that the addition of silk fibroin enhanced the mechanical properties of CS/SF nanofibers. The antibacterial activities against Escherichia coli (Gram negative) and Staphylococcus aureus (Gram positive) were evaluated by the turbidity measurement method; and results suggest that the antibacterial effect of composite nanofibers varied on the type of bacteria. Furthermore, the biocompatibility of murine fibroblast on as-prepared nanofibrous membranes was investigated by hematoxylin and eosin (H&E) staining and MTT assays in vitro, and the membranes were found to promote the cell attachment and proliferation. These results suggest that as-prepared chitosan/silk fibroin (CS/SF) composite nanofibrous membranes could be a promising candidate for wound healing applications.     

Breathable properties of m‐Aramid nanofibrous membrane with high thermal resistance

Electrospinning of m‐aramid in dimethyl acetamide/LiCl solution was investigated to develop thermo‐resistant nanofibrous membranes for breathable waterproof materials. The m‐aramid nanofibers were continuously generated and densely mounted to the membrane without the blockage of the spinning tip during electrospinning. In order to obtain the electrospun m‐aramid nanofibers with different fiber diameters, the polymer concentration in the solution and the spinning distance were varied. Electrospun m‐aramid nanofibrous membranes of various fiber diameters and thicknesses were prepared, and then compared with two commercial expanded polytetrafluoroethylene (ePTFE) membranes with respect to water vapor permeability and pore size. The m‐aramid nanofibrous membrane showed a good water vapor permeability that satisfied the criterion of a breathable membrane, higher than those of the ePTFE porous membranes. Therefore, m‐aramid nanofibrous membrane with thermal and mechanical resistance has great potential for breathable waterproof materials and filters. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41515.     

Solvent-resistant polymeric microfiltration membranes based on oxidized electrospun poly(arylene sulfide sulfone) nanofibers

Polymeric membranes have been widely used in the separation of aqueous system, but there were few studies on the organic solvent-resistant microfiltration (MF) membranes. In this study, organic solvent-resistant oxidized poly(arylene sulfide sulfone)-6 (O-PASS-6) nanofibrous MF membrane with high water flux was prepared through electrospun technology, cold-press, and oxidation treatment. The O-PASS-6 nanofibrous MF membrane was made from the interwoven electrospun uniformly 295 nm nanofibers, and the mean pore size was 0.44 μm. The morphology, chemical structure, and aggregation structure of O-PASS-6 nanofibrous MF membrane were characterized systematically by the scanning electron microscope, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, and X-ray diffraction. Investigations on the weight loss, swelling ratio, and microstructure change all revealed that the O-PASS-6 membrane had superior stability in strong polar solvents, such as 1,3-dimethyl-2-imidazolidinone (DMI), dimethylformamide (DMF), and tetrahydrofuran (THF). MF performance results showed that the pure water flux of O-PASS-6 nanofibrous membrane was up to 753.34 L·m⁻²·h⁻¹, and the rejection ratio was 99.9% to 0.2 μm particles. More importantly, after treated by aggressive solvents, the membranes still possessed good MF performance: the water flux was 770.08, 775.66, and 766.36 L·m⁻²·h⁻¹ when soaked in DMI, DMF, and THF for 7 days, respectively, and high rejection ratio also maintained (>99%) for both particles investigated. The O-PASS-6 membrane with good solvent resistance proved to be a promising candidate as a prefiltration membrane to eliminate submicron particles in both sewage and aggressive solvents. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48506.     

Photocatalytic,piezocatalytic, and piezo-photocatalytic effects in ferroelectric (Ba0.875Ca0.125)(Ti0.95Sn0.05)O3 ceramics

Ba_0.875Ca_0.125Ti_0.95Sn_0.05O₃ (BCT-Sn) was examined for photocatalytic, piezocatalytic, and piezo-photocatalytic effects. BCT-Sn powder was poled through corona poling and it was found that poling induces significant impact on photocatalysis. This material was also able to degrade dye (Methylene blue) using poled powder under ultrasonication (piezocatalysis). There was a remarkable effect in dye degradation which is a clear indication of the importance of piezocatalytic behavior in catalytic reactions. Moreover, the piezo-photocatalytic effect (piezocatalysis + photocatalysis) was also investigated. Results suggested an enormous scope of ferroelectric materials in the field of catalysis.     

Synthesis,antimicrobial activity,and release of tetracycline hydrochloride loaded poly(vinyl alcohol)/soybean protein isolate/zirconium dioxide nanofibrous membranes

Tetracycline hydrochloride loaded poly(vinyl alcohol)/soybean protein isolate/zirconium (Tet–PVA/SPI/ZrO₂) nanofibrous membranes were fabricated via an electrospinning technique. The average diameter of the PVA/soybean protein isolate (SPI)/ZrO₂ nanofibers used as drug carriers increased with increasing ZrO₂ content, and the nanofibers were uneven and tended to stick together when the ZrO₂ content was above 15 wt %. The Tet–PVA/SPI/ZrO₂ nanofibers were similar in morphology when the loading dosage of the model drug tetracycline hydrochloride was below 6 wt %. The PVA, SPI, and ZrO₂ units were linked by hydrogen bonds in the hybrid networks, and the addition of ZrO₂ improved the thermostability of the polymer matrix. The Tet–PVA/SPI/ZrO₂ nanofibrous membranes exhibited good controlled drug‐release properties and antimicrobial activity against Staphylococcus aureus. The results of this study suggest that those nanofibrous membranes were suitable for drug delivery and wound dressing. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40903.     

Immobilization of horseradish peroxidase on electrospun poly(vinyl alcohol)–polyacrylamide blend nanofiber membrane and its use in the conversion of phenol

Electrospun nanofibers, with their porous structures, high surface-to-volume ratio, and good mechanical properties, are used as a support material for enzyme immobilization. In this study, the poly(vinyl alcohol) and polyacrylamide bicomponent (PVA–PAAm) nanofibers were fabricated via the electrospinning method. Synthesized PAAm was characterized with size exclusion chromatography (SEC). Nanofibers were characterized by fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and scanning electron microscope (SEM). DSC and TGA analyses showed that the nanofibers were more durable than PVA and PAAm polymers. SEM images demonstrated that all nanofibers possessed uniform and smooth structures (average diameter about 300 nm). FTIR results have shown that PAAm successfully participates in nanofiber structure. The produced nanofibers were used as support material for covalent immobilization of horseradish peroxidase (HRP). The optimum temperature for free HRP was 45 °C, whereas it was 50 °C for the immobilized enzyme. The immobilized HRP showed better storage and thermal stability than free HRP. The kinetic parameters (K _m and V _max) were found to be 2.42 mM and 0.027 U for the immobilized HRP and 1.86 mM and 0.079 U for the free HRP, respectively. The immobilized enzyme could be used effectively for 25 cycles with 54% retention of the activity. The immobilized HRP was also used for the conversion of phenol. Phenol removal was found to be about 29.68% at 180 min in real wastewater. The novel PVA–PAAm nanofibrous material was successfully used as a support material for covalent immobilization of HRP. Immobilized enzymes such as oxido-reductases onto the PVA–PAAm bicomponent nanofiber could be recommended in the treatment of organic pollutants in industrial effluents.

     

Interaction of human smooth muscle cells on random and aligned nanofibrous scaffolds of PHBV and PHBV-gelatin

Tissue-engineered scaffolds with nanofibrous morphology have been shown to be effective in regeneration of tissues because nanofibers mimic the native architecture of the extracellular matrix. The unique alignment in the native tissue motivated the authors to fabricate aligned nanofibers of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and PHBV-gelatin. The in vitro potential of the scaffolds was evaluated using human smooth muscle cells. MTS study confirmed that PHBV aligned nanofibrous scaffold promotes better cell proliferation as well as gene expression of key contractile and extracellular matrix markers than their PHBV-gelatin counterparts. Hence, the PHBV aligned nanofibers can be used as a biomimetic scaffold for the regeneration of esophagus. Electrospinning system for aligned nanofibers fabrication (A) and interaction of human smooth muscle cells on aligned nanofibers (B).