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"Liu, Gongping"
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Artificial channels for confined mass transport at the sub-nanometre scale
Mass transport at the sub-nanometre scale, including selective transport of gases, liquids and ions, plays a key role in systems such as catalysis, energy generation and storage, chemical sensing and molecular separation. Highly efficient biological channels in living organisms have inspired the design of artificial channels with similar, or even higher, mass-transport efficiency, which can be used at a much larger scale. In this Review, we highlight synthetic-nanomaterials-enabled channels in the platforms of well-defined nanopores, 1D nanotubes and 2D nanochannels, and discuss their design principles, channel architectures and membrane or device fabrication. We focus on fundamental mechanisms of sub-nanometre confined mass transport and their relationships with the structure–property–performance. We then present the practicalities of these channels and discuss their potential impact on the development of next-generation sustainable technologies for use in applications related to energy, the environment and healthcare.
Artificial channels that selectively transport small molecules at the sub-nanometre scale are used in many applications, but, in particular, in molecular separation. This Review discusses the design of channels, nanostructure, fabrication and mass-transport mechanisms, as well as outlining promising applications and the challenges ahead.
Journal Article
Controllable ion transport by surface-charged graphene oxide membrane
Ion transport is crucial for biological systems and membrane-based technology. Atomic-thick two-dimensional materials, especially graphene oxide (GO), have emerged as ideal building blocks for developing synthetic membranes for ion transport. However, the exclusion of small ions in a pressured filtration process remains a challenge for GO membranes. Here we report manipulation of membrane surface charge to control ion transport through GO membranes. The highly charged GO membrane surface repels high-valent co-ions owing to its high interaction energy barrier while concomitantly restraining permeation of electrostatically attracted low-valent counter-ions based on balancing overall solution charge. The deliberately regulated surface-charged GO membranes demonstrate remarkable enhancement of ion rejection with intrinsically high water permeance that exceeds the performance limits of state-of-the-art nanofiltration membranes. This facile and scalable surface charge control approach opens opportunities in selective ion transport for the fields of water transport, biomimetic ion channels and biosensors, ion batteries and energy conversions.
Graphene oxide membranes have great potential in separation processes, but small ions rejection needs improvement for large scale applications. Here the authors manipulate the membrane’s surface charge to control selective ion transport, achieving high rejection for A2B and AB2 type salts and maintaining high water permeance.
Journal Article
Mixed matrix formulations with MOF molecular sieving for key energy-intensive separations
Membrane-based separations can improve energy efficiency and reduce the environmental impacts associated with traditional approaches. Nevertheless, many challenges must be overcome to design membranes that can replace conventional gas separation processes. Here, we report on the incorporation of engineered submicrometre-sized metal–organic framework (MOF) crystals into polymers to form hybrid materials that successfully translate the excellent molecular sieving properties of face-centred cubic (fcu)-MOFs into the resultant membranes. We demonstrate, simultaneously, exceptionally enhanced separation performance in hybrid membranes for two challenging and economically important applications: the removal of CO2 and H2S from natural gas and the separation of butane isomers. Notably, the membrane molecular sieving properties demonstrate that the deliberately regulated and contracted MOF pore-aperture size can discriminate between molecular pairs. The improved performance results from precise control of the linkers delimiting the triangular window, which is the sole entrance to the fcu-MOF pore. This rational-design hybrid approach provides a general toolbox for enhancing the transport properties of advanced membranes bearing molecular sieve fillers with sub-nanometre-sized pore-apertures.
Journal Article
Posterior basolateral amygdala to ventral hippocampal CA1 drives approach behaviour to exert an anxiolytic effect
The basolateral amygdala (BLA) and ventral hippocampal CA1 (vCA1) are cellularly and functionally diverse along their anterior–posterior and superficial-deep axes. Here, we find that anterior BLA (aBLA) and posterior BLA (pBLA) innervate deep-layer calbindin1-negative (Calb1−) and superficial-layer calbindin1-positive neurons (Calb1+) in vCA1, respectively. Photostimulation of pBLA–vCA1 inputs has an anxiolytic effect in mice, promoting approach behaviours during conflict exploratory tasks. By contrast, stimulating aBLA–vCA1 inputs induces anxiety-like behaviour resulting in fewer approaches. During conflict stages of the elevated plus maze task vCA1
Calb1+
neurons are preferentially activated at the open-to-closed arm transition, and photostimulation of vCA1
Calb1+
neurons at decision-making zones promotes approach with fewer retreats. In the APP/PS1 mouse model of Alzheimer’s disease, which shows anxiety-like behaviour, photostimulating the pBLA–vCA1
Calb1+
circuit ameliorates the anxiety in a Calb1-dependent manner. These findings suggest the pBLA–vCA1
Calb1+
circuit from heterogeneous BLA–vCA1 connections drives approach behaviour to reduce anxiety-like behaviour.
Projections from the anterior and posterior basolateral amygdala (pBLA) to the ventral hippocampus CA1 (vCA1) are heterogenous. Here the authors show that activating the pathway from pBLA to vCA1 calbindin 1 positive neurons has an anxiolytic effect in approach-avoidance tasks in mice.
Journal Article
Deformation constraints of graphene oxide nanochannels under reverse osmosis
Nanochannels in laminated graphene oxide nanosheets featuring confined mass transport have attracted interest in multiple research fields. The use of nanochannels for reverse osmosis is a prospect for developing next-generation synthetic water-treatment membranes. The robustness of nanochannels under high-pressure conditions is vital for effectively separating water and ions with sub-nanometer precision. Although several strategies have been developed to address this issue, the inconsistent response of nanochannels to external conditions used in membrane processes has rarely been investigated. In this study, we develop a robust interlayer channel by balancing the associated chemistry and confinement stability to exclude salt solutes. We build a series of membrane nanochannels with similar physical dimensions but different channel functionalities and reveal their divergent deformation behaviors under different conditions. The deformation constraint effectively endows the nanochannel with rapid deformation recovery and excellent ion exclusion performance under variable pressure conditions. This study can help understand the deformation behavior of two-dimensional nanochannels in pressure-driven membrane processes and develop strategies for the corresponding deformation constraints regarding the pore wall and interior.
Nanochannels in laminated graphene oxide nanosheets featuring confined mass transport have attracted interest in multiple research fields. As an important aspect for efficient pressure-driven membrane processes, authors investigate the response and deformation behaviours of such nanochannels to different external conditions.
Journal Article
Improving Balance Between Oxygen Permeability and Stability of Ba0.5Sr0.5Co0.8Fe0.2O3−δ Through High-Entropy Design
Currently, the trade-off between oxygen permeation flux and structural stability in conventional perovskite oxides restricts the practical application of oxygen permeable membranes. In this study, a high-entropy design was applied to the B-site of BSCF matrix materials, resulting in the successful synthesis of a high-entropy perovskite, Ba0.5Sr0.5Co0.71Fe0.2Ta0.03Ni0.03Zr0.03O3−δ. The crystal structure, microstructure, and elemental composition of the material were systematically characterized and analyzed. Theoretical analysis and experimental characterization confirm that the material exhibits a stable single-phase high-entropy perovskite oxide structure. Under He as the sweep gas, the membrane achieved an oxygen permeation flux of 1.28 mL·cm−2·min−1 and operated stably for over 100 h (1 mm thick, 900 °C). In a 20% CO2/He atmosphere, the flux remained above 0.92 mL·cm−2·min−1 for over 100 h, demonstrating good CO2 tolerance. Notably, when the sweep gas is returned to the pure He atmosphere, the oxygen permeation flux fully recovers to 1.28 mL·cm−2·min−1, with no evidence of leakage. These findings indicate that the proposed B-site doping strategy can break the trade-off between oxygen permeability and structural stability in conventional perovskite membranes. This advancement supports the industrialization of oxygen permeable membranes and offers valuable theoretical guidance for the design of high-performance perovskite materials.
Journal Article
Polyolefin reweaved ultra-micropore membrane for CO2 capture
High-performance gas separation membranes have potential in industrial separation applications, while overcoming the permeability-selectivity trade-off via regulable aperture distribution remains challenging. Here, we report a strategy to fabricate Polyolefin Reweaved Ultra-micropore Membrane (PRUM) to acquire regulable microporous channel. Specifically, olefin monomers are dispersed uniformly into a pristine membrane (e.g., PIM-1) via solution diffusion method. Upon controlled electron beam irradiation, the olefin undergoes a free radical polymerization, resulting in the formation of olefin polymer in-situ reweaved in the membrane. The deliberately regulated and contracted pore-aperture size of the membrane can be accomplished by varying the olefin polymer loading to achieve efficient gas separation. For instance, PIM-1 PRUM containing 27 wt% poly-glycidyl methacrylate demonstrate CO
2
permeability of 1976 Barrer, combined with CO
2
/CH
4
and CO
2
/N
2
selectivities of 58.4 and 48.3 respectively, transcending the performance upper bounds. This controllable and high efficiency-design strategy provides a general approach to create sub-nanometre-sized pore-apertures of gas separation membranes with wide universality.
High-performance gas separation membranes have potential in industrial separation applications, but overcoming the permeability-selectivity trade-off via regulable aperture distribution remains challenging. Here, the authors report a strategy to fabricate polyolefin reweaved ultra-micropore membrane to acquire regulable microporous channels.
Journal Article
Mathematical model for the tensile strength of the crimping assembly of aviation wiring harness end
In this study, the relationship between the tensile strength and the indentation depth was studied by analysing the deformation mechanism of the crimping assembly of the aviation wiring harness end. Tensile strength tests were performed on samples of crimping assemblies with different indentation depths. The results showed that the experimental and theoretical values were in good agreement, verifying the validity of the established mathematical model for tensile strength. Based on this model, a reasonable design range for the indentation depth corresponding to the specific combination of contacts and strands was determined.
Journal Article
Surveillance for and Discovery of Borrelia Species in US Patients Suspected of Tickborne Illness
Tick-transmitted Borrelia fall into 2 heterogeneous bacterial complexes comprised of multiple species, the relapsing fever (RF) group and the Borrelia burgdorferi sensu lato group, which are the causative agents of Lyme borreliosis (LB), the most common tickborne disease in the Northern Hemisphere. Geographic expansion of LB in the United States and discovery of emerging Borrelia pathogens underscores the importance of surveillance for disease-causing Borrelia.
De-identified clinical specimens, submitted by providers throughout the United States, for patients suspected of LB, anaplasmosis, ehrlichiosis, or babesiosis were screened using a Borrelia genus-level TaqMan polymerase chain reaction (PCR). Borrelia species and sequence types (STs) were characterized by multilocus sequence typing (MLST) utilizing next-generation sequencing.
Among 7292 specimens tested, 5 Borrelia species were identified: 2 causing LB, B. burgdorferi (n = 25) and B. mayonii (n = 9), and 3 RF borreliae, B. hermsii (n = 1), B. miyamotoi (n = 8), and Candidatus B. johnsonii (n = 1), a species previously detected only in the bat tick, Carios kelleyi. ST diversity was greatest for B. burgdorferi-positive specimens, with new STs identified primarily among synovial fluids.
These results demonstrate that broad PCR screening followed by MLST is a powerful surveillance tool for uncovering the spectrum of disease-causing Borrelia species, understanding their geographic distribution, and investigating the correlation between B. burgdorferi STs and joint involvement. Detection of Candidatus B. johnsonii in a patient with suspected tickborne disease suggests this species may be a previously undetected cause of illness in humans exposed to bat ticks.
Journal Article