Catalytic nanofiber composite membrane by combining electrospinning precursor seeding and flowing synthesis for immobilizing ZIF-8 derived Ag nanoparticles

Advanced solar photo-Fenton-like process with directly growing nano-heterojunctions on graphite fiber felt for phenolic wastewater treatment: Synergistically expand the pH activity range and facilitate the Fe(III)/Fe(II) cycle

Nanoscale FeWO4/BiVO4 heterojunctions were directly grown on the graphite fiber felt (GF) with good conductivity to construct a FeWO4/BiVO4 @GF solar photo-Fenton like wastewater treatment system. The removal effect of COD from phenolic wastewater and the mechanism of synergistic improvement of wastewater treatment efficiency by this system were investigated. The FeWO4/BiVO4 heterojunction prepared by hydrothermal method exhibited higher photoelectric conversion efficiency and solar light utilization rate, thus endowing FeWO4/BiVO4 with excellent solar-Fenton like reaction activity.The photo-Fenton activity can be maintained well even within the pH range of 2-8. Loading FeWO4/BiVO4 nano-heterojunction on GF helped to increase the contact area between Fenton reagents and wastewater, facilitate the electron transfer on the FeWO4/BiVO4 heterojunction and enable the recovery and reuse of the Fenton reagents.Under solar light radiation, the COD removal efficiency of FeWO4/BiVO4 @GF/H2O2 system in phenolic wastewater was more than 92%. Even after five cycles, the system still exhibited excellent operation stability. FeWO4/BiVO4@GF promoted the conversion and cycling of Fe(III)/Fe(II) by accelerating the separation and transport of photogenerated electrons/holes and increasing the concentration of active species, thereby stimulating excellent solar photo-Fenton like activity.The results are significance to the development of green and efficient photo-Fenton process for advanced treatment of industrial wastewater.

Enrichment of Nutmeg Essential Oil from Oil-in-Water Emulsions with PAN-Based Membranes

This study used polyacrylonitrile (PAN) and heat-treated polyacrylonitrile (H-PAN) membranes to enrich nutmeg essential oils, which have more complex compositions compared with common oils. The oil rejection rate of the H-PAN membrane was higher than that of the PAN membrane for different oil concentrations of nutmeg essential oil-in-water emulsions. After heat treatment, the H-PAN membrane showed a smaller pore size, narrower pore size distribution, a rougher surface, higher hydrophilicity, and higher oleophobicity. According to the GC-MS results, the similarities of the essential oils enriched by the PAN and H-PAN membranes to those obtained by steam distillation (SD) were 0.988 and 0.990, respectively. In addition, these two membranes also exhibited higher essential oil rejection for Bupleuri Radix, Magnolia Officinalis Cortex, Caryophylli Flos, and Cinnamomi Cortex essential oil-in-water emulsions. This work could provide a reference for membrane technology for the non-destructive separation of oil with complex components from oil-in-water emulsions.

Architecting N-doped Carbon Nanotube-Rich Carbon Nanofibers with Biomimetic Vine-Leaf-Whisker Structure as Robust Bifunctional Electrocatalysts for Rechargeable Zn-Air Batteries

Efficient and durable bifunctional catalysts toward oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are urgently desirable but challenging for rechargeable Zn-air batteries (ZABs), especially flexible wearable ZABs. Inspired by the vine-leaf-whisker structure in nature, we proposed a three-dimensional (3D) hierarchical bifunctional catalyst (denoted as Co-Fe-Zn@N-CNT/CNF) consisting of N-doped carbon nanotubes embedded with abundant CoFe alloy nanoparticles, leaf-shaped N-doped carbon nanoflakes, and porous carbon fibers for rechargeable ZABs. The special biomimetic structure provides a large specific surface area, allowing for high exposure of the active site and ensuring fast mass transport/charge transfer. The close combination of CoFe bimetallic alloys and N-doped carbon nanotubes delivers high electrocatalytic activity, while the coexistence of various active sites such as metal nanoparticles (NPs), metal-Nx, doped N species, and their synergistic interactions endows the catalysts with more active sites. As such, the Co-Fe-Zn@N-CNT/CNF catalyst achieves superior bifunctional catalytic activities for the ORR (a half-wave potential of 0.84 V) and the OER (an overpotential of 326 mV at 10 mA cm-2) in alkaline media, comparable to commercial Pt/C and RuO2. Remarkably, both aqueous and solid-state ZABs assembled with Co-Fe-Zn@N-CNT/CNF catalysts as air electrodes demonstrate excellent charging/discharging performance, high peak power density, and robust long-term cycling stability. More interestingly, the flexible ZAB performs well even under bending conditions, displaying satisfactory device stability and mechanical flexibility. This study presents a new collective morphological-composition-structural engineering strategy for exploiting the efficient bifunctional oxygen electrocatalysts, which is of great significance for high-performance rechargeable ZABs and wearable energy storage devices.

Biomimetic Ag/ZnO@PDMS Hybrid Nanorod Array-Mediated Photo-induced Enhanced Raman Spectroscopy Sensor for Quantitative and Visualized Analysis of Microplastics

Microplastics are persistent pollutants that accumulate in the environment and can cause serious toxicity to mammals. At present, few technologies are able to quantitatively detect chemicals and provide morphological information simultaneously. Herein, we developed a dragonfly-wing-mimicking ZnO nanorod array decorated with AgNPs on polydimethylsiloxane (PDMS) as a surface-enhanced Raman spectroscopy (SERS) and photo-induced enhanced Raman spectroscopy (PIERS) substrate for trace analysis of microplastics. The Ag/ZnO@PDMS hybrid nanorod array endows the sensor with high sensitivity and signal repeatability (RSD ∼ 5.89%), ensuring the reliable quantitative analysis of microplastics. Importantly, when the noble metal-semiconductor substrate was pre-radiated with ultraviolet light, a surprising PIERS was attained, achieving an additional enhancement of 11.3-fold higher than the normal SERS signal. By combining the PIERS technology with the "coffee ring effect", the sensor successfully discerned microplastics of polyethylene (PE) and polystyrene (PS) at a trace level of 25 μg/mL even with a portable Raman device. It was capable of identifying PS microspheres in contaminated tap water, lake water, river water, and seawater with detection limits of 25, 28, 35, and 60 μg/mL, respectively. The recovery rates of PS microspheres in four water environments ranged from 94.8 to 102.4%, with the RSD ranging from 2.40 to 6.81%. Moreover, quantitative and visualized detection of microplastics was readily realized by our sensor. This portable PIERS sensor represents a significant step toward the generalizability and practicality of quantitative and visual sensing technology.

Functionalized nanofibers in gas sorption process: a critical review on the challenges and prospective research

Air pollution has become the most important environmental and human health threat as it is accounting for about 7 million deaths across the globe every year. Particulate matter (PM) derived from the combustion of fossil fuels, biomass, and other agricultural residues pollutes the atmospheric air which affects the quality of the environment and poses a great threat to human health. Ecological imbalance, climatic variation, and cardiovascular and respiratory problems among humans are significant extortions due to PM pollution. Scientific approaches were initiated to limit the levels of PM in the atmospheric air and the use of nanofiber mats has received wide attention as these possess versatile properties including nanoscale-sized pore structure, homogeneity in their size distribution with high specific surface area, and low basis weight. To exploit their filtration potential towards wide classes of pollutants and also to enhance the capturing efficacy, functionalized nanofibers are currently in practice with tailor-made modifications on the surface. The present review provides a comprehensive report on the different fabrication processes of functionalized nanofibers along with the controlling factors affecting the efficacy of the gas separation process. Also, it provides technical insights on the mass transfer aspects of PM filtration by elucidation their mechanism which can provide vital information on the rate-controlling diffusive flux(es). Conclusively, the practical challenges encountered in the large-scale air filtration systems such as filter cleaning, flow-rate regulation, pressure drop, and extent of reusability are discussed, and the review has identified potential gaps in the current research and can be considered for the prospective research in the area of PM separation process.

Fabrication of Unidirectional Water Permeable PS/PET Composite Nanofibers Modified with Silver Nanoparticles via Electrospinning

In this study, the composite nanofiber membranes (AgNPs-PS/PET) composed of hydrophobic polystyrene (PS) embedded with different additions of silver nanoparticles (AgNPs) and hydrophilic hydrolyzed polyethylene terephthalate (PET) were prepared via electrospinning technology to achieve the function of unidirectional water penetration. The addition of AgNO₃ was at 0 wt%, 0.5 wt%, 1.0 wt% and 1.5 wt% as the variables. The surface morphology and structure of AgNPs-PS/PET composite nanofibers were characterized by scanning electron microscopy (SEM), x-ray energy dispersive spectroscopy (EDS) and transmission electron microscopy (TEM). The SEM image showed that the fibers of the composite materials were continuous and uniform as a result of electrospinning. The presence and content of Ag nanoparticles dispersed in the nanofibers were investigated using EDS and TEM. The contact angle (CA) was tested to illustrate the wettability of the composite nanofiber membranes using a static contact angle measuring instrument and the process of unidirectional water penetration was recorded. Meanwhile, the mechanism of unidirectional water penetration was analyzed. Moreover, the electrospinning solution's viscosity and conductivity were also investigated. Eventually, the optimal addition of AgNO₃ (1.0 wt%) was confirmed and the prepared AgNPs-PS/PET composite nanofiber membranes were able to achieve the function of unidirectional water penetration. These membranes have the potential to be applied in smart textiles, unidirectional water collection and wound dressing.

Ag-O-Co Interface Modulation-Amplified Luminol Cathodic Electrogenerated Chemiluminescence

It remains a great challenge to develop effective strategies for improving the weak cathodic electrogenerated chemiluminescence (ECL) of the luminol-dissolved O₂ system. Interface modulation between metal and supports is an attractive strategy to improve oxygen reduction reaction (ORR) activity. Therefore, the design of electrocatalysts via interface modulation would provide new opportunities for the ECL amplification involving reactive oxygen species (ROSs). Herein, we have fabricated an Ag single-atom catalyst with an oxygen-bridged interface (Ag-O-Co) through the electrodeposition of Ag on a CoAl layered double hydroxide (LDH) modified indium tin oxide (ITO) electrode (Ag^s/LDH/ITO). Interestingly, it was found that the cathodic ECL intensity of the luminol-dissolved O₂ system at the Ag^s/LDH/ITO electrode was extraordinarily enhanced in comparison with those at bare ITO and other Ag nanoparticle-based electrodes. The enhanced ECL performances of the Ag^s/LDH/ITO electrode were attributed to the increasing amounts of ROSs by electrocatalytic ORR in the Ag-O-Co interface. The electron redistribution of Ag and Co bimetallic sites could accelerate electron transfer, promote the adsorption of O₂, and sufficiently activate O₂ through a four-electron reaction pathway. Finally, the luminol cathodic ECL intensity was greatly improved. Our findings can provide inspiration for revealing the interface effects between metal and supports, and open up a new avenue to improve the luminol cathodic ECL.

Study Effect of nAg Particle Size on the Properties and Antibacterial Characteristics of Polysulfone Membranes

Polysulfone ultrafiltration membranes were fabricated using various sizes (20, 40, and 90-210 nm) of silver nanoparticles (nAg) blended in a dope solution. To characterize the performance and properties of the prepared membranes, scanning electron microscopy (SEM), water contact angle, protein separation, water flux, and antibacterial tests were conducted. The characterization results revealed that when nAg particles (20 nm) were blended into the base polymer PSF, the PSF/nAg blended membrane had the lowest contact angle (58.5°) and surface energy (110.7 mN/m). When experimenting with ultrafiltration using protein solutions, bare PSF and PSF/nAg-20 blended membranes gave similar values of protein rejection: 93% of bovine serum albumin (BSA) and 70% of lysozyme rejection. Furthermore, SEM studies showed that the surface pore size was reduced by adding 20 nm nAg particles in the casting solution. Most importantly, the introduction of 40 nm nAg particles reduced the growth of bacterial colonies on the membrane surface by up to 72%. These findings revealed that nAg particles are expected to be a potential modifier for the fabrication of an ultrafiltration membrane.