Latest ArticlesPoly(m-phthaloyl-m-phenylenediamine) (PMIA) is promising as the separator in lithium-ion batteries (LIBs) for its excellent thermostability, insulation and self-extinguishing properties. However, its low mechanical strength and poor electrolyte affinity limit its application in LIBs. In this work, a new PMIA@polyacrylonitrile-polyvinylidene fluoride hexafluoropropylene-titanium dioxide (PMIA@PAN/PVDF-HFP/TiO2) composite fibrous separator with a coaxial core-shell structure was developed by combining coaxial electrospinning, hot pressing, and heat treatment techniques. This separator not only inherits the exceptional thermostability of PMIA, showing no evident thermal shrinkage at 220 ℃, but also reveals improved mechanical strength (29.7 MPa) due to the formation of firm connections between fibers with the melted PVDF-HFP. Meanwhile, the massive polar groups in PVDF-HFP play a vital role in improving the electrolyte affinity, which renders the separator a high ionic conductivity of 1.36 × 10−3 S/cm. Therefore, the LIBs with PMIA@PAN/PVDF-HFP/TiO2 separators exhibited excellent cycling and rate performance at 25 ℃, and a high capacity retention rate (76.2%) at 80 ℃ for 200 cycles at 1 C. Besides, the lithium metal symmetric battery assembled by the separator showed a small overpotential, indicating that the separator had a role in inhibiting lithium dendrites. In short, the PMIA@PAN/PVDF-HFP/TiO2 separator possesses a wide application prospect in the domain of LIBs.
Optimal bulk-heterojunction (BHJ) morphology is crucial for efficient charge transport and good photovoltaic performance in organic solar cells (OSCs). Yet, the correlation between chemical structures of nonfullerene acceptors (NFAs) and molecular interaction in the BHJ blends remains opaque. Herein, we study three isomeric NFAs referred to as MQ1-x (x = β, γ, or δ) that shared an asymmetric selenophene-fused heteroheptacene backbone end-capped by two monochlorinated end groups. Remarkably, miscibility between the polymer donor of PM6 and MQ1-x successively elevates as the chlorine atoms move from β-, to γ-, to δ-position of terminals. Combined with the varied molecular crystallinity of these NFAs, diverse BHJ morphologies are observed in their blend films. As a result, the MQ1-δ-based devices present the highest PCE of 12.08% owing to the efficient charge dissociation and transport induced by the compact molecular packing and optimal BHJ morphology. Our investigation provides a new insight in the material design that has a good balance in molecular packing and film morphology for high-performance OSCs.
A novel solid–liquid-core fiber-optic biosensor was fabricated for highly sensitive and selective detection of 4-chlorophenol in water. The sensor comprised horseradish peroxidase (HRP)-coated U-shaped liquid-core optical fiber (LCOF) and 4-chlorophenol permselective polymer membrane. The U-shaped LCOF was filled with ethanol suspension of SiO2 particles and the polymer membrane was composed of molecularly imprinted polymer, sulfonated polyethersulfone, and polysulfone. The morphology, composition, and surface luminous properties of the sensing region were examined. The effects of the diameter and content of SiO2 particles and temperature of 4-chlorophenol solutions on the sensitivity of the biosensors were investigated. Further, the sensitivity, selectivity, response time, and limit of detection (LOD) of the biosensors was investigated. In addition, the effects of fiber core materials on the light transmission in sensing region were investigated and a biosensor sensing model was established. The proposed sensor exhibited high selectivity for 4-chlorophenol with satisfactory sensitivity, LOD, and response time: -1.18 (µg/L)−1, 30 µg/L, and 400 s, respectively. The results are expected to aid in the development of methods for enhancing sensitivity of fiber-optic sensors and surface luminous intensity of optical fibers.
P2-type layered oxides are receiving significant interest due to their superior structure and intrinsic performances. There are strenuous attempts to balance the structure stability, phase transition as well as desirable electrochemical performances by inducing anion/cation ions, changing morphology, adjusting valence, etc. In this work, several same-period elements of Sc, Ti, V, Cr, Fe, Cu and Zn are doped into Na0.50Li0.08Mn0.60Co0.16Ni0.16O2 cathodes, which are manipulated by ions radii and valence state, further studied by operando X-ray powder diffraction patterns (XRD). As a result, the Cu2+ doped cathode performed higher rate capacities (as high as 86 mAh/g even at 10 C) and more stable structures (capacity retention of ~89.4% for 100 cycles), which owing to the synergistic effect among the tightened TMO2 layer, enlarged d-spacing, reduce OO electrostatic repulsion, ameliorate lattice distortion as well as mitigate ordering of Na+/vacancy.
Single-atomic catalysts (SACs) caught considerable attention due to their unique structural properties, complete exposed active site, and 100% atom utilization efficiency with remarkable catalytic activity. Mesoporous single-atomic cobalt catalyst with Co-N4 active sites was synthesized by using nitrogen-doped graphene derived from acrylonitrile. Single-atomic cobalt was observed by aberration-corrected high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) in Co@Nx-C-800. Notably, the density functional theory (DFT) calculation and the extended X-ray absorption fine structures (EXAFS) fitting results indicate that the coordination structure of Co-N is four-coordinated. In this work, the practical hydrogenation of nitroarenes to anilines enabled by Co@Nx-C-800 was established with excellent yields and selectivity, which proved its advantages and potential applications.
Environmental economics is accelerating the urgency to develop recycling technologies for the ever-growing quantity of discarded thermoset polymers. Herein, we developed a mild and energy-saving process for high-efficiency degradation and reuse of anhydride-cured epoxy thermoset with the aid of hydrazine hydrate. The degradation degree of the epoxy resin reached 99.6% at 120 ℃ within a short time of 60 min. During the reaction, the ester bonds in the cross-linked network were selectively cleaved by the amination of hydrazine hydrate, and the epoxy resin was fully converted to new monomers that contained hydrazide and hydroxyl groups, respectively. Moreover, the degradation mechanism of the epoxy resin in hydrazine hydrate was studied and a nucleation model was utilized to predict the actual degradation behavior of the system. Finally, the degradation products can be directly mixed with epoxy precursor to prepare a new waterborne epoxy coating with good comprehensive properties. This work not only demonstrates a new way to realize the efficient degradation of epoxy resins, but also provides a facile and efficient recycling protocol for thermosets.
Generally, the metal sulfide itself has poor conductivity, and the volume expansion occurs when it is converted with sodium, which will destroy the integrity of the electrode structure, resulting in poor cycle performance and rate performance. To solve the problems of low initial coulombic efficiency (ICE) and volume expansion of metal compounds used as anodes in sodium-ion batteries (SIBs). Inspired by nature, the CoSO4/hard carbon/graphene (CHG) fractal structure electrode was designed. Self-fractal structures with electron/ion transport channels and high strain tolerance proved to be an effective strategy to overcome these challenges. The fractal dimension (D) is measured by synchronous Small Angle X-ray scattering, and the D remains stable during charging and discharging. The fractal CHG also showed excellent electrochemical performance, especially 97.4% ICE. Theoretical calculation shows that self-fractal CHG can promote the formation of a thin solid electrolyte interface (SEI). Synchrotron radiation absorption spectrum proved the reaction mechanism of CHG. This study not only proves that cobalt sulfate is a feasible strategy for developing high-performance SIBs anodes but also provides an advanced method for measuring the fractal dimension of energy storage electrode materials.
DNA-based supramolecular hydrogels are important and promising biomaterials for various applications due to their inherent biocompatibility and tunable physicochemical properties. The three-dimensional supramolecular matrix of DNA formed by non-covalently dynamic cross-linking provides exceptional adaptability, self-healing, injectable and responsive properties for hydrogels. In addition, DNA hydrogels are also ideal bio-scaffold materials owing to their tissue-like mechanics and intrinsic biological functions. Technically, DNA can assemble into supramolecular networks by pure complementary base pairing; it can also be combined with other building blocks to construct hybrid hydrogels. This review focuses on the development and construction strategies of DNA hydrogels. Assembly and synthesis methods, diverse responsiveness and biomedical applications are summarized. Finally, the challenges and prospects of DNA-based supramolecular hydrogels are discussed.
Transition metal and nitrogen co-doped carbons (M-N-C) have proven to be promising catalysts for CO2 electroreduction into CO because of the high activity and selectivity. Effective enrichment of the active transition metal coordinated nitrogen sites is desirable but is challenging for a practical volumetric productivity. Herein, we report four kinds of model electrocatalysts to unveil this issue, which include the NC structures with surface N-functionalities, Ni-N-C_I with one layer of surface Ni-N3C sites, NC@Ni-N-C_I with surface N-functionalities and underneath Ni-N3C sites as well as Ni-N-C_II with doubled surface Ni-N3C sites. The X-ray absorption spectroscopy indicates the coordination configuration of Ni-N3C. For NC catalysts, when N-doping level increased from 3.5 at% to 8.4 at%, the CO partial current density increased from below 0.1 mA/cm2 to 3 mA/cm2. Introducing one layer of Ni-N3C onto the NC structures leads to a 54 times higher CO partial current density than that of NC, in the meantime the FECO is 66 times higher. Furthermore, doubling the density of surface Ni-N3C sites by a layer-by-layer method doubles the CO partial current density (jCO), indicating its potential to achieve a high density of active coordinated sites and current densities.
Three-dimensional (3D) histology has exhibited tremendous potential in fundamental research and clinical disease grading, but compatible labeling techniques are still lacking. Recently in Science Advances, Pac et al. report a new histological technique termed 3DNFC, which realizes 3D fluorescence imaging of thick tissues via citrate-based in situ fluorophore formation.
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