It is still a challenge to prepare a water- and polymer-based electrospun air filter film with high efficiency filtration, low pressure drop, and good mechanical properties. To address this issue, polyvinyl alcohol (PVA) was employed as the main material, mixing polyethyleneimine (PEI), bamboo-based activated carbon (BAC) and cellulose nanocrystal (CNC) to construct the air filter film by electrostatic electrospinning. In this system, the negatively charged BAC and CNC are fixed in the system through bonding with the positively charged PEI, showing a double adsorption effect. One is the mechanical filtration of the porous network structure constructed by PVA@PEI electrospun nanofibers, and the other is the electrostatic adsorption of PM2.5 on the surface of BAC and CNC. It is significant that the resulting composite air filter displays a high filtration efficiency of 95.86%, a pressure drop of only 59 Pa, and good thermal stability. Moreover, the introduced methyltrimethoxysilane (MTMS) endows it with good water-resistance. Given these excellent performances, this system can provide theoretical and technical references for the development of water- and polymer-based electrospun air filter film.
Uncontrolled hemorrhage resulting from traumas causes severe health risks. There is an urgent need for expeditious hemostatic materials to treat bleeding incidents. Here, we developed a natural protein-based hemostatic sponge extracted from nonmulberry cocoons that exhibited rapid coagulation and effective absorption. We first built a degumming and dissolution system suitable for the Dictyoploca japonica cocoons to obtain regenerated silk fibroin (DSF). The DSF was then combined with carboxymethyl chitosan (CMCS) by glutaraldehyde (GA) crosslinking to ensure the structural stability of sponges. The resulting DSF–CMCS–GA exhibited remarkable hemostatic properties, displaying the highest absorption rate. It also demonstrated comparable efficacy to commercial hemostatic sponges. The blood-clotting index and hemolysis test showed that the prepared sponge possessed hemostatic activity and good hemocompatibility. Compared with mulberry silk fibroin hemostatic sponges (SF–CMCS–GA), DSF–CMCS–GA showed slightly better effects, making them a potential alternative to mulberry silk. In conclusion, our study introduces the use of Dictyoploca japonica silk fibroin for hemostasis, highlighting the exploitation of wild silkworm resources and providing an excellent silk fibroin-based hemostatic sealant for acute accident wounds and biomedical applications involving massive hemorrhage.
Herein, a novel visible-light-responsive photocatalyst with high efficiency was firstly synthesized at room temperature. The mild synthetic method resulted in a uniform spherical triazine-based covalent organic framework (TrCOF2) with ultra-high specific surface area as well as chemical stability. Due to the synergistic effect between the self-assembled uniform spherical structure and the abundant triazine-based structure, photoelectron–hole pairs were efficiently separated and migrated on the catalysts. On this basis, TrCOF2 was successfully applied to efficiently degrade bisphenol A (BPA). More than 98% of BPA was deraded after 60 min of visible light treatment, where the active specie of •O2 − played a vital role during the degradation of BPA. The holes of TrCOF2 could produce O2 by direct reaction with water or hydroxide ions. Simultaneously, photoelectrons can be captured by O2 to generate •O2 −. Moreover, density functional theory (DFT) calculations proved the outstanding ability of the exciting electronic conductivity. Remarkably, a reasonable photocatalytic mechanism for TrCOF2 catalysts was proposed. This research can provide a facile strategy for the synthesis of TrCOFs catalysts at room temperature, which unfolds broad application prospects in the environmental field.
Flexible humidity sensors are widely used in many fields, such as environmental monitoring, agricultural soil moisture content determination, food quality monitoring and healthcare services. Therefore, it is essential to measure humidity accurately and reliably in different conditions. Flexible materials have been the focusing substrates of humidity sensors because of their rich surface chemical properties and structural designability. In addition, flexible materials have superior ductility for different conditions. In this review, we have summarized several sensing mechanisms, processing techniques, sensing layers and substrates for specific humidity sensing requirements. Aadditionally, we have sorted out some cases of flexible humidity sensors based on different functional materials. We hope this paper can contribute to the development of flexible humidity sensors in the future.
Tin dioxide nanotubes with N-doped carbon layer (SnO2/N-C NTs) were synthesized through a MoO3 nanorod-based sacrificial template method, dopamine polymerization and calcination process. Applied to the Li-ion battery, SnO2/N-C NTs exhibited excellent electrochemical properties, with a first discharge capacity of 1722.3 mAh·g−1 at 0.1 A·g−1 and a high capacity of 1369.3 mAh·g−1 over 100 cycles. The superior electrochemical performance is ascribed to the N-doped carbon layer and tubular structure, which effectively improves the electrical conductivity of the composites, accelerates the migration of Li+ and electrons, and alleviates the volume change of the anode to a certain extent.
As a structural and functional material with excellent properties, ceramics play an extremely important role in a wide range of industries, including life and production. To expand the range of applications for ceramic materials, ceramics are often joined to metals and then used. Among the physical and chemical joining methods of ceramics to metals, the AMB method is efficient and simple, suitable for industrial applications, and has been a hot topic of research. However, due to the problems of residual stresses caused by the large difference in thermal expansion coefficients between ceramic and metal brazing, composite fillers have become a very worthwhile solution by regulating the physical properties of the brazing material and improving the weld structure. This review describes the wetting principle and application of Ag‒Cu‒Ti active metal filler in the field of ceramic joining, with emphasis on the current stage of composite filler, and discusses the influence on the former brazing properties and organization after the introduction of dissimilar materials.
Flexible strain sensors have been extensively used in human motion detection, medical aids, electronic skins, and other civilian or military fields. Conventional strain sensors made of metal or semiconductor materials suffer from insufficient stretchability and sensitivity, imposing severe constraints on their utilization in wearable devices. Herein, we design a flexible strain sensor based on biphasic hydrogel via an in-situ polymerization method, which possesses superior electrical response and mechanical performance. External stress could prompt the formation of conductive microchannels within the biphasic hydrogel, which originates from the interaction between the conductive water phase and the insulating oil phase. The device performance could be optimized by carefully regulating the volume ratio of the oil/water phase. Consequently, the flexible strain sensor with oil phase ratio of 80% demonstrates the best sensitivity with gauge factor of 33 upon a compressive strain range of 10%, remarkable electrical stability of 100 cycles, and rapid resistance response of 190 ms. Furthermore, the human motions could be monitored by this flexible strain sensor, thereby highlighting its potential for seamless integration into wearable devices.
Pore characteristics have been identified as key design parameters for osteoimmunomodulation. The strategy reported here is to create an appropriate immune microenvironment by regulating pore characteristics of scaffolds, thereby promoting early angiogenesis and enhancing osteogenesis. A series of collagen/nano-hydroxyapatite (Col/nHAP) composite scaffolds with ordered lamellar structures and different layer spacings were prepared by mimicking the ordered lamellar topology of the bone matrix. Our research indicated that the layer spacing and ordered topology of the scaffold exerted an important influence on phenotype transformation of macrophages and the secretion of angiogenic factors. The Col/nHAP-O(135) with large layer spacing not only supported cell attachment and diffusion in vitro, but also promoted early angiogenesis by timely switching from M1 to M2 macrophage phenotype. In vivo data showed that the layer spacing and the ordered structure of the scaffold synergistically regulated the inflammatory response and triggered macrophages to secrete more angiogenesis related cytokines. Col/nHAP-O(135) considerably promoted the neovascularization and new bone formation in the defect site, indicating that Col/nHAP-O(135) could significantly enhance the osteogenic activity of stem cells with the involvement of macrophages.
Monoclonal antibodies have been used in many diseases, but how to improve their delivery efficiency is still a key issue. As the modification of zwitterionic polymers can maintain the stability and biological activity of monoclonal antibodies, in this study, zwitterionic monomers, sulfobetaine methacrylate (SBMA), and 3-[[2-(methacryloyloxy) ethyl] dimethylammonio] propionate (CBMA) were used to prepare monoclonal antibody-loaded zwitterionic nanoparticles with the aid of the crosslinker of MMP-2 enzyme-responsive peptide which was a rapid synthesis process under mild conditions. The results from dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM) indicated that a series of zwitterionic nanoparticles had been successfully prepared by the in situ free radical polymerization using the MMP-2 enzyme-responsive peptide as the cross-linking agent. These nanoparticles were spherical with the sizes of (18.7±1.9) nm (SBMA nanoparticle) and (18.2±2.1) nm (CBMA nanoparticle), and the surface contained zwitterionic polymers. It was revealed that they had no cytotoxicity, could be released in tumor microenvironment by enzyme to inhibit the growth of tumor cells, and was able to effectively penetrate endothelial cells (> 2%) by transwell. Therefore, the development of this strategy has a great prospect for the delivery of monoclonal antibodies.
Rechargeable aqueous zinc-ion batteries (AZIBs) are the most promising candidates for the energy storage due to their high safety, rich resources, and large specific capacity. However, AZIBs using neutral or slightly acidic electrolytes still face side effects and zinc dendrites on the anode surface. To stabilize the Zn anode, a chemically stable and multi-functional coating of polyvinylidene fluoride (PVDF) and 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) was prepared on the Zn surface. The anhydride groups in 6FDA can improve the hydrophilicity, promoting the migration of zinc ions. Besides, PVDF is compatible with 6FDA because of the presence of organic F-containing groups, which can also effectively reduce the nucleation overpotential and exhibit the dendrite-free Zn deposition/stripping. The PVDF/6FDA@Zn symmetric cell can cycle for 5000 h at a current density of 0.5 mA·cm−2, maintaining the extremely low polarization voltage and overpotential of 28 and 8 mV, respectively. The PVDF/6FDA@Zn||MnO2 full cell can remain a specific capacity of ~90 mAh·g−1 after 2000 cycles at 1.5 A·g−1. This simple method achieves a reversible Zn anode, providing an inspiring strategy for ultra-long-cycle AZIBs.
Nitrogen atom doping has been found to enhance the electrochemical performance of porous carbon (PC). In this study, hollow tubular nitrogen-doped porous carbon (N/PC) was synthesized using polyvinylpyrrolidone as the carbon–nitrogen source and fibrous brucite as the template through carbonization. The effects of nitrogen and argon protective atmospheres on the nitrogen content, the specific surface area (SSA), and electrochemical properties of N/PC were investigated. The results showed that compared with N/FBC-Ar, N/FBC-N2 prepared in nitrogen protective atmosphere had a higher nitrogen content and a larger proportion of pyrrolic nitrogen (N-5) and pyridinic nitrogen (N-6). N/FBC-N2 displayed a specific capacitance (C) of 194.1 F·g−1 at 1 A·g−1, greater than that of N/FBC-Ar (174.3 F·g−1). This work reveals that the nitrogen doping with a higher nitrogen content in nitrogen protective atmosphere is more favorable. Furthermore, a larger proportion of pyrrolic nitrogen and pyridinic nitrogen in the doped nitrogen atoms significantly enhances the electrochemical performance.
Electrospun nanofibers with highly efficient photothermal/electrothermal performance are extremely popular because of their great potential in wearable heaters. However, the lack of necessary wearable properties such as high mechanical strength and quick response of electrospun micro/nanofibers seriously affects their practical application. In this work, a technical route combining electrospinning and surface modification technology is proposed. The 3-triethoxysilylpropylamine-polyacrylonitrile@copper sulfide (K-PAN@CuS) composite fabric was achieved by modifying the original electrospinning PAN fiber and subsequently loading CuS nanoparticles. The results show that the break strength of the K-PAN@CuS fabric was increased by 10 times compared to that of the original PAN@CuS fabric. Furthermore, the saturated temperature of the K-PAN@CuS fabric heater could reach 116 °C within 15 s at a relatively low voltage of 3 V and 120.3 °C within 10 s under an infrared therapy lamp (100 W). In addition, due to its excellent conductivity, such a unique structural design enables the fiber to be closely attached to the human skin and helps to monitor human movements. This K-PAN@CuS fabric shows great potential in wearable heaters, hyperthermia, all-weather thermal management, and in vitro physical therapy.
