Two-dimensional (2D) graphitic carbon nitride (g-C N ) nanosheets show brilliant application potential in numerous fields. Herein, a membrane with artificial nanopores and self-supporting spacers was fabricated by assembly of 2D g-C N nanosheets in a stack with elaborate structures. In water purification the g-C N membrane shows a better separation performance than commercial membranes. The g-C N membrane has a water permeance of 29 L m h bar and a rejection rate of 87 % for 3 nm molecules with a membrane thickness of 160 nm. The artificial nanopores in the g-C N nanosheets and the spacers between the partially exfoliated g-C N nanosheets provide nanochannels for water transport while bigger molecules are retained. The self-supported nanochannels in the g-C N membrane are very stable and rigid enough to resist environmental challenges, such as changes to pH and pressure conditions. Permeation experiments and molecular dynamics simulations indicate that a novel nanofluidics phenomenon takes place, whereby water transport through the g-C N nanosheet membrane occurs with ultralow friction. The findings provide new understanding of fluidics in nanochannels and illuminate a fabrication method by which rigid nanochannels may be obtained for applications in complex or harsh environments.

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Electrospinning using natural proteins and synthetic polymers offers an attractive technique for producing fibrous scaffolds with potential for tissue regeneration and repair. Nanofibrous scaffolds of silk fibroin (SF) and poly(L-lactic acid-co-epsilon-caprolactone) (P(LLA-CL)) blends were fabricated using 1,1,1,3,3,3-hexafluoro-2-propanol as a solvent via electrospinning. The average nanofibrous diameter increased with increasing polymer concentration and decreasing the blend ratio of SF to P(LLA-CL). Characterizations of XPS and (13)C NMR clarified the presence of SF on their surfaces and no obvious chemical bond reaction between SF with P(LLA-CL) and SF in SF/P(LLA-CL) nanofibers was present in a random coil conformation, SF conformation transformed from random coil to beta-sheet when treated with water vapor. Whereas water contact angle measurements conformed greater hydrophilicity than P(LLA-CL). Both the tensile strength and elongation at break increased with the content increasing of P(LLA-CL). Cell viability studies with pig iliac endothelial cells demonstrated that SF/P(LLA-CL) blended nanofibrous scaffolds significantly promoted cell growth in comparison with P(LLA-CL), especially when the weight ratio of SF to P(LLA-CL) was 25:75. These results suggested that SF/P(LLA-CL) blended nanofibrous scaffolds might be potential candidates for vascular tissue engineering.

In this study, a series of nanofibrous membranes were prepared from cellulose acetate (CA) and polyester urethane (PEU) using coelectrospinning or blend-electrospinning. The drug release, in vitro antimicrobial activity and in vivo wound healing performance of the nanofiber membranes were evaluated for use as wound dressings. To prevent common clinical infections, an antimicrobial agent, polyhexamethylene biguanide (PHMB) was incorporated into the electrospun fibers. The presence of CA in the nanofiber membrane improved its hydrophilicity and permeability to air and moisture. CA fibers became slightly swollen upon contacting with liquid phase. CA not only increased the liquid uptake but also created a moist environment for the wound, which accelerated wound recovery. PHMB release dynamics of the membranes was controlled by the structure and component ratios of the membranes. The lower ratio of CA: PEU helped to preserve the physical and thermal properties of the membranes, and also reduced the burst release effectively and slowed down diffusion of PHMB during in vitro tests. The controlled-diffusion membranes exerted long-term antimicrobial effect for wound healing.

This work presents a simple and reliable method for directly generating polyvinylidene fluoride (PVDF) nanofibers with secondary surface morphology (e.g., porous surfaces, rough surfaces, grooved surfaces, and interior porosity) by using single/binary solvent systems and relative humidity. We clarified the mechanisms responsible for the formation of these morphologies by systematically exploring the molecular interactions among the polymer, solvent(s), and water vapor. Our results proved that the formation of secondary surface morphology needed the presence of water vapor, a non-solvent of the polymer, at an appropriate level of relative humidity. The formation of secondary surface morphology was dependent on the speed of evaporation of the solvent(s) (ACE, DMF, and their mixtures), as well as the inter-diffusion and penetration of the non-solvent (water) and solvent(s). The results of N2 physical adsorption-desorption isotherms showed that the macro-porous fibers (> 300 nm) exhibited the highest specific surface area of 23.31 ± 4.30 m2/g and pore volume of 0.0695 ± 0.007 cm3/g, enabling the high oil absorption capacities of 50.58 ± 5.47 g/g, 37.74 ± 4.33 g/g, and 23.96 ± 2.68 g/g for silicone oil, motor oil, and olive oil, respectively. We believe this work may serve as guidelines for the formation of different structures of macro-porous, rough, and grooved nanofibers with interior porosity through electrospinning.Electronic supplementary materialThe online version of this article (10.1186/s11671-018-2705-0) contains supplementary material, which is available to authorized users.

Particulate matter (PM) pollution has become a serious threat to public health, climate and ecosystems.Therefore, filtration materials with high filtration efficiency and low air resistance are in urgent need. Electret filters that can significantly improve filtration efficiency without increasing pressure drop are widely used for air filtration. However, long-term maintenance of the electrical charges on electret filters, particularly at high temperatures and in wet conditions, is still a challenge. Herein, we report the fabrication of a novel electret filter with a fluffy structure, high porosity and satisfactory filtration stability using polypropylene (PP) as the matrix polymer and magnesium stearate (MgSt) as the charge enhancer. Benefiting from the fluffy structure created by melt blown at a large die-to-collector distance (DCD), the pressure drop decreased from 67.0 Pa to 52.9 Pa at an air flow rate of 85 L min À1

Harvesting energy has been attracting the attention of researchers in recent years. This work comprehensively reports the fabrication and characterization of poly(vinylidene fluoride) fiber webs with comparable diameters and diversified surface morphologies (wrinkled, smooth, and porous) based on randomly oriented and aligned fiber webs which are used as active layers to directly make a piezoelectric nanogenerator (PENG). The results show that wrinkled fibers are preferable fiber webs for the PENG owing to their outstanding properties represented by high fibers friction, supreme β phase content (F[β]), and interior pores. Furthermore, we found that the electrical outputs of the PENG based on aligned fiber webs are higher than those based on randomly oriented fiber webs due to the increase in the friction area. The electrical outputs of the PENG based on the aligned wrinkled fiber webs are able to run microelectronic devices when it subjected to a mechanical impact. We believe that our study may inspire the research area for future energy harvesting applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47049.