Structural Engineering of Hierarchical Magnetic/Carbon Nanocomposites via In Situ Growth for High-Efficient Electromagnetic Wave Absorption.

Materials exhibiting high-performance electromagnetic wave absorption have garnered considerable scientific and technological attention, yet encounter significant challenges. Developing new materials and innovative structural design concepts is crucial for expanding the application field of electromagnetic wave absorption. Particularly, hierarchical structure engineering has emerged as a promising approach to enhance the physical and chemical properties of materials, providing immense potential for creating versatile electromagnetic wave absorption materials. Herein, an exceptional multi-dimensional hierarchical structure was meticulously devised, unleashing the full microwave attenuation capabilities through in situ growth, self-reduction, and multi-heterogeneous interface integration. The hierarchical structure features a three-dimensional carbon framework, where magnetic nanoparticles grow in situ on the carbon skeleton, creating a necklace-like structure. Furthermore, magnetic nanosheets assemble within this framework. Enhanced impedance matching was achieved by precisely adjusting component proportions, and intelligent integration of diverse interfaces bolstered dielectric polarization. The obtain Fe3O4-Fe nanoparticles/carbon nanofibers/Al-Fe3O4-Fe nanosheets composites demonstrated outstanding performance with a minimum reflection loss (RLmin) value of - 59.3 dB and an effective absorption bandwidth (RL ≤ - 10 dB) extending up to 5.6 GHz at 2.2 mm. These notable accomplishments offer fresh insights into the precision design of high-efficient electromagnetic wave absorption materials.

Genome-wide identification and expression analysis of VQ gene family under abiotic stress in Coix lacryma-jobi L.

BACKGROUND: Valine-glutamine (VQ) proteins are non-specific plant proteins that have a highly conserved motif: FxxhVQxhTG. These proteins are involved in the development of various plant organs such as seeds, hypocotyls, flowers, leaves and also play a role in response to salt, drought and cold stresses. Despite their importance, there is limited information available on the evolutionary and structural characteristics of VQ family genes in Coix lacryma-jobi. RESULTS: In this study, a total of 31 VQ genes were identified from the coix genome and classified into seven subgroups (I-VII) based on phylogenetic analysis. These genes were found to be unevenly distributed on 10 chromosomes. Gene structure analysis revealed that these genes had a similar type of structure within each subfamily. Moreover, 27 of ClVQ genes were found to have no introns. Conserved domain and multiple sequence alignment analysis revealed the presence of a highly conserved sequences in the ClVQ protein. This research utilized quantitative real-time PCR (qRT-PCR) and promoter analysis to investigate the expression of ClVQ genes under different stress conditions. Results showed that most ClVQ genes responded to polyethylene glycol, heat treatment, salt, abscisic acid and methyl jasmonate treatment with varying degrees of expression. Furthermore, some ClVQ genes exhibited significant correlation in expression changes under abiotic stress, indicating that these genes may act synergistically in response to adversarial stress. Additionally, yeast dihybrid verification revealed an interaction between ClVQ4, ClVQ12, and ClVQ26. CONCLUSIONS: This study conducted a genome-wide analysis of the VQ gene family in coix, including an examination of phylogenetic relationships, conserved domains, cis-elements and expression patterns. The goal of the study was to identify potential drought resistance candidate genes, providing a theoretical foundation for molecular resistance breeding.

Bio-Inspired Aramid Fibers@silica Binary Synergistic Aerogels with High Thermal Insulation and Fire-Retardant Performance.

Flame-retardant, thermal insulation, mechanically robust, and comprehensive protection against extreme environmental threats aerogels are highly desirable for protective equipment. Herein, inspired by the core (organic)-shell (inorganic) structure of lobster antenna, fire-retardant and mechanically robust aramid fibers@silica nanocomposite aerogels with core-shell structures are fabricated via the sol-gel-film transformation and chemical vapor deposition process. The thickness of silica coating can be well-defined and controlled by the CVD time. Aramid fibers@silica nanocomposite aerogels show high heat resistance (530 °C), low thermal conductivity of 0.030 W·m-1·K-1, high tensile strength of 7.5 MPa and good flexibility. More importantly, aramid fibers@silica aerogels have high flame retardancy with limiting oxygen index 36.5. In addition, this material fabricated by the simple preparation process is believed to have potential application value in the field of aerospace or high-temperature thermal protection.

Bioinspired Hairy Crab Claw Polymer Surface with Excellent Self-Cleaning Wettability in Muddy or Oil-Contaminated Water.

The hairy crab Eriocheir sinensis lives in muddy freshwaters such as ponds and paddy fields. The crab's claw features dense patches of setae and exhibits an excellent self-cleaning surface in muddy waters. This study examined the micronano structure and wettability properties of the crab claw. The results showed that the claw consists of 3D cross-linked fibers with a hierarchical micronano structure, and the main chemical composition of these fibers was determined chitosan molecules. The claw also has special superoleophobic and self-cleaning properties in muddy water. Inspired by the structure of the crab claw, 3D-layered micro/nanostructures with poly(vinyl alcohol)/chitosan/poly(N-isopropylacrylamide) were prepared by electrospinning and in situ polymerization. This novel bioinspired polymer surface exhibits superhydrophilicity in the air, superoleophobicity underwater (with an oil contact angle of 163°), and excellent self-cleaning potential in muddy water.

Ancient Chemistry "Pharaoh's Snakes" for Efficient Fe-/N-Doped Carbon Electrocatalysts.

The method of fabricating nonprecious metal electrocatalysts with high activity and durability through a facile and eco-friendly procedure is of great significance to the development of low-cost fuel cells and metal-air batteries. Herein, we present that an ancient chemical reaction of "Pharaoh's snakes" can be a fast and convenient technique to prepare Fe-/N-doped carbon (Fe/N-C) nanosheet/nanotube electrocatalysts with sugar, soda, melamine, and iron nitrate as precursors. The resultant Fe/N-C catalyst has a hierarchically porous structure, a large surface area, and uniformly distributed active sites. The catalyst shows high electrocatalytic activities toward both the oxygen reduction reaction with a half-wave potential of 0.90 V (vs reversible hydrogen electrode) better than that of Pt/C and the oxygen evolution reaction with an overpotential of 0.46 V at the current density of 10 mA cm-2 comparable to that of RuO2. The activity and stability of the catalyst are also evaluated in primary and rechargeable Zn-air batteries. In both conditions, three-dimensional Fe/N-C exhibited performances superior to Pt/C. Our work demonstrates a success of utilizing an ancient science to make a state-of-the-art electrocatalyst.

Polypyrrole Whelk-Like Arrays toward Robust Controlling Manipulation of Organic Droplets Underwater.

Whelk-like polypyrrole (PPy) arrays film is successfully prepared by electropolymerization of pyrrole in the presence of low-surface-energy tetraethylammonium perfluorooctanesulfonate (TEAPFOS) as dopant. The underwater wettability of PPy whelk-like arrays can be successfully tuned by electrical doping/dedoping of PFOS ions. Interestingly, CCl4 droplets with microliter-size as a representative sample are gathered together to form a larger droplet underwater at the potential of +0.8 V (vs Ag/AgCl), because PPy is in its PFOS-doped states. Note that CCl4 droplet can climb uphill successfully on the inclined whelk-like arrays PPy film under the applied potential of -1.0 V (vs Ag/AgCl), which may be attributed to wettability gradient derived from different oxidation states of PPy induced by electrochemical potential. These results may provide a simple strategy for on-demand manipulation of organic droplets underwater at low voltage.

Porous Core-Shell Fe3C Embedded N-doped Carbon Nanofibers as an Effective Electrocatalysts for Oxygen Reduction Reaction.

The development of nonprecious-metal-based electrocatalysts with high oxygen reduction reaction (ORR) activity, low cost, and good durability in both alkaline and acidic media is very important for application of full cells. Herein, we developed a facile and economical strategy to obtain porous core-shell Fe3C embedded nitrogen-doped carbon nanofibers (Fe3C@NCNF-X, where X denotes pyrolysis temperature) by electrospinning of polyvinylidene fluoride (PVDF) and FeCl3 mixture, chemical vapor phase polymerization of pyrrole, and followed by pyrolysis of composite nanofibers at high temperatures. Note that the FeCl3 and polypyrrole acts as precursor for Fe3C core and N-doped carbon shell, respectively. Moreover, PVDF not only plays a role as carbon resources, but also provides porous structures due to hydrogen fluoride exposure originated from thermal decomposition of PVDF. The resultant Fe3C@NCNF-X catalysts, particularly Fe3C@NCNF-900, showed efficient electrocatalytic performance for ORR in both alkaline and acidic solutions, which are attributed to the synergistic effect between Fe3C and N-doped carbon as catalytic active sites, and carbon shell protects Fe3C from leaching out. In addition, the Fe3C@NCNF-X catalyst displayed a better long-term stability, free from methanol crossover and CO-poisoning effects than those of Pt/C, which is of great significance for the design and development of advanced electrocatalysts based on nonprecious metals.

High Performance Heteroatoms Quaternary-doped Carbon Catalysts Derived from Shewanella Bacteria for Oxygen Reduction.

A novel heteroatoms (N, P, S and Fe) quaternary-doped carbon (HQDC-X, X refers to the pyrolysis temperature) can be fabricated by directly pyrolyzing a gram-negative bacteria, S. oneidensis MR-1 as precursors at 800 °C, 900 °C and 1000 °C under argon atmosphere. These HQDC-X catalysts maintain the cylindrical shape of bacteria after pyrolysis under high temperatures, while heteroatoms including N, P, S and Fe distribute homogeneously on the carbon frameworks. As a result, HQDC-X catalysts exhibit excellent electrocatalytic activity for ORR via a dominant four-electron oxygen reduction pathway in alkaline medium, which is comparable with that of commercial Pt/C. More importantly, HQDC-X catalysts show better tolerance for methanol crossover and CO poisoning effects, long-term durability than commercial Pt/C, which could be promising alternatives to costly Pt-based electrocatalysts for ORR. The method may provide a promising avenue to develop cheap ORR catalysts from inexpensive, scalable and biological recursors.

Stable underwater superoleophobic and low adhesive polypyrrole nanowire mesh in highly corrosive environments.

Underwater superoleophobic materials with low adhesion have been widely researched owing to their self-cleaning and anti-corrosive properties. In this study, polypyrrole (PPy) nanowire meshes have been successfully fabricated by in situ electrochemical polymerization on stainless steel mesh substrates in the presence of phosphate buffered saline as both an electrolyte and a dopant. PPy nanowire meshes have high oil contact angles (above 150°) and low sliding angles (less than 10°), and they show underwater superoleophobicity with an excellent self-cleaning performance, not only in pure water, but also in highly corrosive aqueous solutions, including salt solutions, strong acids or basic solutions. PPy nanowire meshes presented here show promise for potential applications in fields such as oil-water separation and marine oil spill clean-up.

Centimeter-scale colloidal crystal belts via robust self-assembly strategy.

Centimeter-scale poly(acrylic acid-co-DVB80) (PAA) 3D colloidal crystal belts were prepared via a novel robust vertical deposition technique based on negative pressure and curvature substrate of the glass vial. The formation of PAA colloidal crystal belts was investigated. The results indicated that curvature could control the dimension of PAA colloidal crystal belts. Well-controlled negative pressure resulted in rapid fabrication of well-defined PAA colloidal crystal belts. Curvature substrate of glass vial could distribute shrinking stress in the process of drying of colloidal films. Strong hydrogen bonding interactions among carboxyl groups on the surface of PAA colloidal particles was responsible for PAA colloidal crystal belts with closed-packing characteristics.

Controlled dispersion of silver nanoparticles into the bulk of thermosensitive polymer microspheres: tunable plasmonic coupling by temperature detected by surface enhanced Raman scattering.

By in situ reduction of Ag(+) ions pre-dispersed inside thermosensitive microspheres of poly[(N-isopropylacrylamide)-co-(methacrylic acid)] (P(NIPAM-co-MAA)), a 3D copolymer-supported network of silver nanoparticles is created and extensively characterized by surface-enhanced Raman scattering (SERS). The effective dispersion and the suitable density of the silver nanoparticles in the composite microspheres are demonstrated by the thermal-induced SERS signal and its high reproducibility during thermocycling. When the temperature of the system increases above 32 °C, spatial separation of the silver nanoparticles decreases and the numbers of Ag nanoparticles and P(NIPAM-co-MAA) microspheres under illumination spot increase as a result of the shrinkage of the P(NIPAM-co-MAA) chains, leading to the ramp of the SERS effect. By means of the high reversibility of the thermosensitive phase transition of the P(NIPAM-co-MAA) microspheres, SERS activity of the silver nanoparticle network embedded in the microsphere can be well controlled by thermal-induced variation of special separation.

Monodispersed magnetic polystyrene beads with excellent colloidal stability and strong magnetic response.

Monodispersed polystyrene beads incorporated with Fe(3) O(4) nanoparticles are prepared via dispersion polymerization. The resultant magnetic beads present well-defined composite structures, excellent colloidal stability, and strong magnetic response. The formation mechanism for the monodispersed composite beads, incorporated with preformed Fe(3) O(4) nanocrystals, was investigated. The potential applications of the monodispersed magnetic beads in bacteria capturing were demonstrated. After being coated with anti-Salmonella CSA-1 antibody, the magnetic beads show capturing efficiencies of >99.4% in isolating Salmonella sp.

Superdispersible PVP-coated Fe3O4 nanocrystals prepared by a "one-pot" reaction.

Poly( N-vinyl-2-pyrrolidone) (PVP)-coated Fe3O4 nanocrystals were prepared by a "one-pot" synthesis through the pyrolysis of ferric triacetylacetonate (Fe(acac)3) in N-vinyl-2-pyrrolidone (NVP). The polymerization of NVP was followed by measuring the shear viscosity of the reaction mixture. The PVP molecules formed in the reaction mixture was investigated by gel permeation chromatography. As the resultant Fe3O4 nanocrystals presented superdispersibility in 10 different types of organic solvents and aqueous solutions with different pH, including 0.01 M phosphate-buffered saline buffer, their hydrodynamic properties in both organic and aqueous systems were investigated by dynamic light-scattering. The results indicated that the PVP-coated Fe3O4 nanocrystals can completely be dispersed forming stable colloidal solutions in both organic solvents and water. Fourier transform infrared spectroscopy results suggested that PVP interacted with Fe3O4 via its carbonyl groups. Further surface analysis by X-ray photoelectron spectroscopy revealed that there were both coordinating and noncoordinating segments of PVP on the particle surface; the molar ratio between them was of 1:2.6.