Influence of photothermal nanomaterials localization within the electrospun membrane structure on purification of saline oily wastewater based on photothermal vacuum membrane distillation.

Today, synergistic combination of special nanomaterials (NMs) and electrospinning technique has emerged as a promising strategy to address both water scarcity and energy concerns through the development of photothermal membranes for wastewater purification and desalination. This work was organized to provide a new perspective on membrane design for photothermal vacuum membrane distillation (PVMD) through optimizing membrane performance by varying the localization of photothermal NMs. Poly(vinylidene fluoride) omniphobic photothermal membranes were prepared by localizing graphene oxide nanosheets (GO NSh) (1) on the surface (0.2 wt%), (2) within the nanofibers structure (10 wt%) or (3) in both positions. Considering the case 1, after 7 min exposure to the 1 sun intensity light, the highest temperature (∼93.5 °C) was recorded, which is assigned to the accessibility of GO NSh upon light exposure. The case 3 yielded to a small reduction in surface temperature (∼90.4 °C) compared to the case 1, indicating no need to localize NMs within the nanofibers structure when they are localized on the surface. The other extreme belonged to the case 2 with the lowest temperature of ∼71.3 °C, which is consistent with the less accessibility of GO NSh during irradiation. It was demonstrated that the accessibility of photothermal NMs plays more pronounced role in the membrane surface temperature compared to the light trapping. However, benefiting from higher surface temperature during PVMD due to enhanced accessibility of photothermal NMs is balanced out by decrease in the permeate flux (case 1: 1.51 kg/m2 h and case 2: 1.83 kg/m2 h) due to blocking some membrane surface pores by the binder. A trend similar to that for flux was also followed by the efficiency. Additionally, no change in rejection was observed for different GO NSh localizations.

Dual Functional Antibacterial-Antioxidant Core/Shell Alginate/Poly(ε-caprolactone) Nanofiber Membrane: A Potential Wound Dressing.

Core/shell nanofibers offer the advantage of encapsulating multiple drugs with different hydrophilicity in the core and shell, thus allowing for the controlled release of pharmaceutic agents. Specifically, the burst release of hydrophilic drugs from such fiber membranes causes an instantaneous high drug concentration, whereas a long and steady release is usually desired. Herein, we tackle the problem of the initial burst release by the generation of core/shell nanofibers with the hydrophilic antibiotic drug gentamycin loaded within a hydrophilic alginate core surrounded by a hydrophobic shell of poly(ε-caprolactone). Emulsion electrospinning was used as the nanofibrous mesh generation procedure. This process also allows for the loading of a hydrophobic compound, where we selected a natural antioxidant molecule, betulin (BTL), to detoxify the radicals. The resulting nanofibers exhibited a cylindrical shape with a core/shell structure. In vitro tests showed a controlled release of gentamicin from nanofibers via diffusion. The drug reached 93% release in an alginate hydrogel film but only 50% release in the nanofibers, suggesting its potential to minimize the initial burst release. Antibacterial tests revealed significant activity against both Gram-negative and Gram-positive bacteria. The antioxidant property of betulin was confirmed through the DPPH assay, where the incorporation of 20% BTL revealed 37.3% DPPH scavenging. The nanofibers also exhibited favorable biocompatibility in cell culture studies, and no harmful effects on cell viability were observed. Overall, this research offers a promising approach to producing core/shell nanofibrous mats with antibacterial and antioxidant properties, which could effectively address the requirements of wound dressings, including infection prevention and wound healing acceleration.

Emulsion electrospinning of sodium alginate/poly(ε-caprolactone) core/shell nanofibers for biomedical applications.

Electrospun nanofibers have shown great potential as drug vehicles and tissue engineering scaffolds. However, the successful encapsulation of multiple hydrophilic/hydrophobic therapeutic compounds is still challenging. Herein, sodium alginate/poly(ε-caprolactone) core/shell nanofibers were fabricated via water-in-oil emulsion electrospinning. The sodium alginate concentration, water-to-oil ratio, and surfactant concentration were optimized for the maximum stability of the emulsion. The results demonstrated that an increasing water-to-oil ratio results in more deviation from Newtonian fluid and leads to a broader distribution of the fibers' diameters. Moreover, increasing poly(ε-caprolactone) concentration increases loss and storage moduli and increases the diameter of the resulting fibers. The nanofibers' characteristics were investigated by scanning electron microscopy, transmission electron microscopy, confocal laser scanning microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and water contact angle measurements. It was observed that using an emulsion composition of 10% (w/v) PCL and a water-to-oil ratio of 0.1 results in smooth, cylindrical, and uniform core/shell nanofibers with PCL in the shell and ALG in the core. The in vitro cell culture study demonstrated the favorable biocompatibility of nanofibers. Overall, this study provides a promising and trustworthy material for biomedical applications.

Improved performance of Bis-GMA dental composites reinforced with surface-modified PAN nanofibers.

In the present work, polyacrylonitrile (PAN) nanofibers reinforced dental composites were investigated to achieve the improved interfacial adhesion between the PAN nanofiber and resin matrix using surface modification of nanofibers. PAN nanofibers mat were prepared by electrospinning and then, surface treated with the activated bisphenol A glycidyl methacrylate (Bis-GMA)/triethyleneglycol dimethacrylate (TEGDMA) (50/50 mass ratio) dental resin followed by photo-curing. Also, the treated nanofibers mat was milled into a powder to achieve the uniform distribution of nanofibers in the matrix resin. The reinforced dental composite were prepared by mixing the various mass fraction of the powder (0.5-15 wt%) with the Bis-GMA/TEGDMA dental monomers. The effect of weight ratio of surface-modified nanofibers to blend resin on the chemical structure, morphology, compression and flexural properties, color and polymerization shrinkage of dental composites was evaluated. The results showed that using surface-treated nanofibers with content of 5 wt% enhanced the compression strength, flexural strength, flexural modulus and work of rupture of the resultant dental composite by factors of 23%, 7%, 80%, and 145%, respectively, comparing to the unreinforced neat resin. Also, the polymerization shrinkage reduces by 37%. These significant improved properties of the dental composite could be due to the semi-interpenetration network formation between surface-modified nanofibers and resin matrix and well distribution of nanofibers in the dental resin. Further increasing the nanofiber content led to poor mechanical properties of obtained dental composites. The results also, revealed that the color of resin composite could be whiter using modified PAN nanofibers as the filler.

Pyridinium-based ionic liquid/water mixture intended for efficient dissolution of cellulose, chitosan and chitin: The pivotal contribution of water.

An acidic ionic liquid (IL), i.e. 1-(carboxymethyl)pyridinium chloride, is synthesized and investigated for its untapped potential to dissolve cellulose, chitosan and chitin with concentrations of up to 11, 10 and 5 wt.%, respectively. Interestingly, the optimum water content of the IL/water towards efficient dissolution is determined to be as high as 40 wt.%, which is in evident contrast to the previous reports for other ILs by which the dissolution of polysaccharides is achieved at the expense of water content. Using high water content in IL/water mixture makes a breakthrough in ease of solution processability and dissolution cost reduction. Regenerated cellulose and chitosan have less crystallinity and lower temperature of thermal degradation onset (Tons) compared to the initial samples. The regenerated cellulose exhibits reduction in degree of polymerization, crystallinity and Tons by 55.1%, 11.0% and 38.2%, respectively. Chitin in addition to dissolution, is also hydrolyzed to quaternary ammonium chitosan.

Phase formation of nanolaminated Mo2AuC and Mo2(Au1-xGax)2C by a substitutional reaction within Au-capped Mo2GaC and Mo2Ga2C thin films.

Au-containing nanolaminated carbides Mo2AuC and Mo2(Au1-xGax)2C were synthesized by a thermally induced substitutional reaction in Mo2GaC and Mo2Ga2C, respectively. The Au substitution of the Ga layers in the structures was observed using cross-sectional high-resolution scanning transmission electron microscopy. Expansion of c lattice parameters was also observed in the Au-containing phases compared to the original phases. Energy dispersive spectroscopy detected residual Ga in Au-substituted layers of both phases with a peculiar Ga in-plane ordering for Au : Ga = 9 : 1 ratio along the Au-Ga layers in Mo2(Au1-xGax)2C. These results indicate a generalization of the Au substitution reaction for the A elements in MAX phases.

Synthesis of Ti3AuC2, Ti3Au2C2 and Ti3IrC2 by noble metal substitution reaction in Ti3SiC2 for high-temperature-stable Ohmic contacts to SiC.

The large class of layered ceramics encompasses both van der Waals (vdW) and non-vdW solids. While intercalation of noble metals in vdW solids is known, formation of compounds by incorporation of noble-metal layers in non-vdW layered solids is largely unexplored. Here, we show formation of Ti3AuC2 and Ti3Au2C2 phases with up to 31% lattice swelling by a substitutional solid-state reaction of Au into Ti3SiC2 single-crystal thin films with simultaneous out-diffusion of Si. Ti3IrC2 is subsequently produced by a substitution reaction of Ir for Au in Ti3Au2C2. These phases form Ohmic electrical contacts to SiC and remain stable after 1,000 h of ageing at 600 °C in air. The present results, by combined analytical electron microscopy and ab initio calculations, open avenues for processing of noble-metal-containing layered ceramics that have not been synthesized from elemental sources, along with tunable properties such as stable electrical contacts for high-temperature power electronics or gas sensors.

Untapped potentials of acrylonitrile-butadiene-styrene/polyurethane (ABS/PU) blend membrane to purify dye wastewater.

Production of acrylonitrile-butadiene-styrene/polyurethane (ABS/PU) blend membrane with high rejection efficiency for disperse and vat dyes, is introduced as a facile and cost effective technique to purify textile wastewater. In this respect, membranes are produced using commercially available polymers, i.e. ABS and PU, with different compositions (ABS/PU: 100/0, 80/20, 70/30, 60/40 and 50/50 w/w) through wet casting. Casting solutions with concentration of 30 wt% are prepared using two different solvents, i.e. dimethylformamide (DMF) and N-methyl-2- pyrrolidone (NMP). The prepared membranes are characterized using a variety of analytical techniques including SEM imaging, FTIR spectroscopy, dry and wet gas permeation, evaluation of reusability, antifouling and mechanical properties, photostability, surface hydrophilicity and pure water permeability (PWP) of the produced membranes. According to the results, irrespective of solvent type, ABS/PU membranes with higher PU content have lower porosity and smaller pore size both of which contribute to enhanced dye rejection efficiency. This is while the impact of PU content on the photostability of ABS/PU membranes was found to be negligible. Additionally, the produced ABS/PU membranes exhibit good reusability and antifouling properties. However, the mechanical properties of ABS/PU membranes with higher PU contents are inferior to those with lower PU contents. This contrast highlights the prominence of optimum PU content to make a trade-off between dye rejection efficiency and mechanical properties. In this regard, ABS/PU (60/40 w/w) membrane is recognized as the one with optimum composition. Furthermore, it was found that regardless of PU content, membranes cast from DMF-based solutions exhibit superior rejection performance over those cast from NMP-based solutions. Overall, one can witness that employing ABS/PU membranes provides a meritorious and clean approach to refine disperse and vat dye wastewaters, a great threat to the environment and human health.

Designing the inner surface corrugations of hollow fibers to enhance CO2 absorption efficiency.

For the first time, a low cost strategy is introduced to enhance the efficiency of CO2 absorption using gas-liquid membrane contactors. This is implemented by designing the corrugations in the inner layer of poly(vinyl chloride) hollow fibers (PVC HFs) through changing the bore fluid composition. In fact, the number of corrugations in the HF inner layer is engineered via changing the phase separation time within the inner layer. Such that expedited phase separation leads to highly corrugated inner layer. In contrast, decelerated phase separation is responsible for reduced number of inner layer corrugations. Phase separation causes the initial polymer solution with low viscoelastic moduli to be transferred into polymer-rich domains with high viscoelastic moduli. These domains resist against stretching-induced radial forces toward the center of HF; therefore, the inner layer of HF buckles. Delayed phase separation defers formation of polymer-rich domains and hence, HF with less corrugated inner surface is expected. The phase separation within the HF inner layer is controlled through changing the rate of solvent/nonsolvent exchange. This is conducted by variation the solvent content in the bore fluid; as higher as solvent content, as slower as solvent/nonsolvent exchange.