State‐of‐the‐art proton exchange membranes (PEMs) often suffer from significantly reduced conductivity under low relative humidity, hampering their efficient application in fuel cells. Covalent ...organic frameworks (COFs) with pre‐designable and well‐defined structures hold promise to cope with the above challenge. However, fabricating defect‐free, robust COF membranes proves an extremely difficult task due to the poor processability of COF materials. Herein, a bottom‐up approach is developed to synthesize intrinsic proton‐conducting COF (IPC‐COF) nanosheets (NUS‐9) in aqueous solutions via diffusion and solvent co‐mediated modulation, enabling a controlled nucleation and in‐plane‐dominated IPC‐COF growth. These nanosheets allow the facile fabrication of IPC‐COF membranes. IPC‐COF membranes with crystalline, rigid ion nanochannels exhibit a weakly humidity‐dependent conductivity over a wide range of humidity (30–98%), 1–2 orders of magnitude higher than that of benchmark PEMs, and a prominent fuel cell performance of 0.93 W cm−2 at 35% RH and 80 °C arising from superior water retention and Grotthuss mechanism‐dominated proton conduction.
A bottom‐up approach based on the diffusion and solvent co‐mediated growth of covalent organic frameworks (COFs) is proposed to synthesize nanosheets of a highly crystalline, intrinsically proton‐conducting COF (IPC‐COF) in aqueous solution. The high‐quality IPC‐COF nanosheets allow the fabrication of defect‐free and robust IPC‐COF membranes that exhibit a weakly humidity‐dependent proton conduction and a prominent fuel‐cell performance.
Developing new materials for the fabrication of proton exchange membranes (PEMs) for fuel cells is of great significance. Herein, a series of highly crystalline, porous, and stable new covalent ...organic frameworks (COFs) have been developed by a stepwise synthesis strategy. The synthesized COFs exhibit high hydrophilicity and excellent stability in strong acid or base (e.g., 12 m NaOH or HCl) and boiling water. These features make them ideal platforms for proton conduction applications. Upon loading with H3PO4, the COFs (H3PO4@COFs) realize an ultrahigh proton conductivity of 1.13×10−1 S cm−1, the highest among all COF materials, and maintain high proton conductivity across a wide relative humidity (40–100 %) and temperature range (20–80 °C). Furthermore, membrane electrode assemblies were fabricated using H3PO4@COFs as the solid electrolyte membrane for proton exchange resulting in a maximum power density of 81 mW cm−2 and a maximum current density of 456 mA cm−2, which exceeds all previously reported COF materials.
Conducting COFs: A stepwise synthesis strategy for the preparation of a series of highly robust COFs with ultrahigh proton conduction was developed. These COFs achieved a record‐high proton conductivity (1.13×10−1 S cm−1) after doping with H3PO4 and were used as the proton exchange membrane of a membrane electrode assembly, which achieved a maximum power output of 81 mW cm−1.
The emergence of all‐organic frameworks is of fundamental significance, and designing such structures for anion conduction holds great promise in energy conversion and storage applications. Herein, ...inspired by the efficient anion transport within organisms, a de novo design of covalent organic frameworks (COFs) toward ultrafast anion transport is demonstrated. A phase‐transfer polymerization process is developed to acquire dense and ordered alignment of quaternary ammonium‐functionalized side chains along the channels within the frameworks. The resultant self‐standing COFs membranes exhibit one of the highest hydroxide conductivities (212 mS cm−1 at 80 °C) among the reported anion exchange membranes. Meanwhile, it is found that shorter, more hydrophilic side chains are favorable for anion conduction. The present work highlights the prospects of all‐organic framework materials as the platform building blocks in designing ion exchange membranes and ion sieving membranes.
The de novo design of covalent organic frameworks (COFs) affords a dense and ordered alignment of quaternary ammonium‐functionalized side chains along the intrinsic channels within the frameworks, rendering one of the highest hydroxide conductivities among the reported anion‐exchange membranes (AEMs), and demonstrating the feasibility of COFs as the building blocks for high‐performance AEMs.
The heterogeneity of disease is a major concern in medical research and is commonly characterized as subtypes with different pathogeneses exhibiting distinct prognoses and treatment effects. The ...classification of a population into homogeneous subgroups is challenging, especially for complex diseases. Recent studies show that gut microbiome compositions play a vital role in disease development, and it is of great interest to cluster patients according to their microbial profiles. There are a variety of beta diversity measures to quantify the dissimilarity between the compositions of different samples for clustering. However, using different beta diversity measures results in different clusters, and it is difficult to make a choice among them. Considering microbial compositions from 16S rRNA sequencing, which are presented as a high-dimensional vector with a large proportion of extremely small or even zero-valued elements, we set up three simulation experiments to mimic the microbial compositional data and evaluate the performance of different beta diversity measures in clustering. It is shown that the Kullback-Leibler divergence-based beta diversity, including the Jensen-Shannon divergence and its square root, and the hypersphere-based beta diversity, including the Bhattacharyya and Hellinger, can capture compositional changes in low-abundance elements more efficiently and can work stably. Their performance on two real datasets demonstrates the validity of the simulation experiments.
Nafion, as a state-of-the-art solid electrolyte for proton exchange membrane fuel cells (PEMFCs), suffers from drastic decline in proton conductivity with decreasing humidity, which significantly ...restricts the efficient and stable operation of the fuel cell system. In this study, the proton conductivity of Nafion at low relative humidity (RH) was remarkably enhanced by incorporating multifunctional graphene oxide (GO) nanosheets as multifunctional fillers. Through surface-initiated atom transfer radical polymerization of sulfopropyl methacrylate (SPM) and poly(ethylene glycol) methyl ether methacrylate, the copolymer-grafted GO was synthesized and incorporated into the Nafion matrix, generating efficient paths at the Nafion–GO interface for proton conduction. The Lewis basic oxygen atoms of ethylene oxide (EO) units and sulfonated acid groups of SPM monomers served as additional proton binding and release sites to facilitate the proton hopping through the membrane. Meanwhile, the hygroscopic EO units enhanced the water retention property of the composite membrane, conferring a dramatic increase in proton conductivity under low humidity. With 1 wt % filler loading, the composite membrane displayed the highest proton conductivity of 2.98 × 10–2 S cm–1 at 80 °C and 40% RH, which was 10 times higher than that of recast Nafion. Meanwhile, the Nafion composite exhibited a 135.5% increase in peak power density at 60 °C and 50% RH, indicating its great application potential in PEMFCs.
Graphene oxide (GO) membrane, bearing well-aligned interlayer nanochannels and well-defined physicochemical properties, promises fast proton transport. However, the deficiency of proton donor groups ...on the basal plane of GO and weak interlamellar interactions between the adjacent nanosheets often cause low proton conduction capability and poor water stability. Herein, we incorporate sulfonated graphene quantum dots (SGQD) into GO membrane to solve the above dilemma via synergistically controlling the edge electrostatic interaction and in-plane π–π interaction of SGQD with GO nanosheets. SGQD with three different kinds of electron-withdrawing groups are employed to modulate the edge electrostatic interactions and improve the water swelling resistant property of GO membranes. Meanwhile, SGQD with abundant proton donor groups assemble on the sp2 domain of GO via in-plane π–π interaction and confer the GO membranes with low-energy-barrier proton transport channels. As a result, the GO membrane achieves an enhanced proton conductivity of 324 mS cm–1, maximum power density of 161.6 mW cm–2, and superior water stability when immersed into water for one month. This study demonstrates a strategy for independent manipulation of conductive function and nonconductive function to fabricate high-performance proton exchange membranes.
In this study, a well-designed polysulfone with dense phenyl groups surrounding its backbone (designated as P(ES1-co-ES2)) was synthesized and then modified with abundant quaternary ammoniums (QA). ...The QA functionalized P(ES1-co-ES2) was added to QA functionalized poly (ether ether ketone) with N,N,N',N'-tetramethyl-1,6-hexanediamine (TMHDA) as crosslinking reagent to fabricate anion exchange imembranes (AEM). The incorporation of abundant QA groups substantially increased the ion exchange capacity of the blend membranes. Meanwhile, the densely QA functionalized P(ES1-co-ES2) acted as “hydroxide ion wires” in blend membranes, constructing efficient ion channels for high-speed ion transfer. High hydroxide conductivity up to 215.4mScm−1 at 90°C and the maximum power density of single fuel cell up to 137.2mWcm−2 at 60°C were thus achieved. In addition, the strong covalent interaction caused by TMHDA led to significantly enhanced physical stability (anti-swelling, tensile strength and elongation etc.), while the steric hindrance by the long aliphatic chain of TMHDA enhanced the chemical stability of the blend membranes. This study presents a novel AEM with simultaneously enhanced hydroxide conductivity, physical and chemical stabilities.
The objective of this study is to exploit the one-dimension structure and good proton conduction of phosphorylated silica nanotubes for high proton conductivity of proton exchange membrane (PEM). ...Three types of poly(vinylphosphonic acid-co-divinylbenzene)/silica nanotubes with different aspect ratios are synthesized and incorporated into the sulfonated poly(ether ether ketone) (SPEEK) matrix to prepare composite membranes. The poly(vinylphosphonic acid) segments in the nanotubes could construct facile proton-conduction pathway along this one-dimensional nanostructure. The nanotubes with high aspect ratio exhibit more pronounced effect in elevating the proton conductivity of membranes, revealing the importance of continuity of conduction pathway on proton transport. The membrane incorporated with the nanotubes of the largest aspect ratio of 45.9 exhibits the highest proton conductivity of 0.1032 S cm−1 at 30 °C, 100% RH, which was 84% higher than that of SPEEK control membrane. Moreover, the nanotubes can reduce the methanol permeability, and improve mechanical stability of the membranes.
•Poly(phosphonic acid)/silica nanotubes with diverse aspect ratios were prepared.•The nanotubes were incorporated into SPEEK to prepare composite membrane.•Effect of aspect ratios of the nanotubes on proton conductivity was studied.•The composite membranes showed enhanced proton conductivity and stability.
Autism spectrum disorder (ASD) is characterized by deficits in social interactions and repetitive, stereotypic behaviors. Evidence shows that bidirectional communication of the gut-brain axis plays ...an important role. Here, we recruited 62 patients with ASD in southern China, and performed a cross-sectional study to test the relationship between repeated behavior, gut microbiome composition, and alpha diversity. We divided all participants into two groups based on the clustering results of their microbial compositions and found
and
as the seed genera in each group. Repetitive behavior differed between clusters, and cluster 2 had milder repetitive symptoms than Cluster 1. Alpha diversity between clusters was significantly different, indicating that cluster 1 had lower alpha diversity and more severe repetitive, stereotypic behaviors. Repetitive behavior had a negative correlation with alpha diversity. We demonstrated that the difference in intestinal microbiome composition and altered alpha diversity can be associated with repetitive, stereotypic behavior in autism. The role of
and
in ASD is not yet understood.
Saliva plays a crucial role in shaping the compatibility of piercing-sucking insects with their host plants. Understanding the complex composition of leafhopper saliva is important for developing ...effective and eco-friendly control strategies for the tea green leafhopper,
Fabrecius, a major piercing-sucking pest in Chinese tea plantations. This study explored the saliva proteins of tea green leafhopper adults using a custom collection device, consisting of two layers of Parafilm stretched over a sucrose diet. A total of 152 proteins were identified using liquid chromatography-tandem mass spectrometry (LC-MS/MS) following the filter-aided sample preparation (FASP). These proteins were categorized into six groups based on their functions, including enzymes, transport proteins, regulatory proteins, cell structure proteins, other proteins, and unknown proteins. Bioinformatics analyses predicted 16 secreted proteins, which were successfully cloned and transcriptionally analyzed across various tissues and developmental stages. Genes encoding putative salivary secretory proteins, including
,
,
,
,
, low-density lipoprotein receptor-related protein (
),
, and
, exhibited high expressions in salivary gland (SG) tissues and feeding-associated expressions at different developmental stages. These findings shed light on the potential elicitors or effectors mediating the leafhopper feeding and defense responses in tea plants, providing insights into the coevolution of tea plants and leafhoppers. The study's conclusions open avenues for the development of innovative leafhopper control technologies that reduce the reliance on pesticides in the tea industry.
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