Lamellar Membranes Research Articles

Two dimensional MoS2 finding its way towards constructing high-performance alkaline recovery membranes

The available alkaline recovery membranes are currently dominated by polymeric materials, but they suffer from a permeation-selectivity trade-off and inferior chemical resistance. Robust two dimensional (2D) lamellar membranes with sub-nanometer wide channels are promising candidates for discerning OH− and other anions. Here, we report the development of alkaline recycling membranes through stacking MoS2 nanosheets. Benefiting from the ordered and narrow 2D channels, MoS2 membranes show excellent alkaline recovery performances. The OH− dialysis coefficient (UOH-) and separation factor (S) towards simulated OH− and WO42- across the 500 nm thick MoS2 laminates reach 6.9 × 10−3 m·h−1 and 34.3 respectively. Furthermore, the chemical environments of MoS2 laminates were modulated by intercalating ionic poly(sodium 4-styrene sulfonate) (PSS@MoS2). The UOH- and S values of PSS@MoS2 membrane further improve to 11.7 × 10−3 m·h−1 and 49.8 respectively. Besides, both MoS2 and PSS@MoS2 membranes exhibit promising stability.

Melatonin modulates the Warburg effect and alters the morphology of hepatocellular carcinoma cell line resulting in reduced viability and migratory potential

AimsHepatocellular Carcinoma (HCC) is a primary neoplasm derived from hepatocytes with low responsiveness and recurrent chemoresistance. Melatonin is an alternative agent that may be helpful in treating HCC. We aimed to study in HuH 7.5 cells whether melatonin treatment exerts antitumor effects and, if so, what cellular responses are induced and involved. Main methodsWe evaluated the effects of melatonin on cell cytotoxicity and proliferation, colony formation, morphological and immunohistochemical aspects, and on glucose consumption and lactate release. Key findingsMelatonin reduced cell motility and caused lamellar breakdown, membrane damage, and reduction in microvillus. Immunofluorescence analysis revealed that melatonin reduced TGF and N-cadherin expression, which was further associated with inhibition of epithelial-mesenchymal transition process. In relation to the Warburg-type metabolism, melatonin reduced glucose uptake and lactate production by modulating intracellular lactate dehydrogenase activity. SignificanceOur results indicate that melatonin can act upon pyruvate/lactate metabolism, preventing the Warburg effect, which may reflect in the cell architecture. We demonstrated the direct cytotoxic and antiproliferative effect of melatonin on the HuH 7.5 cell line, and suggest that melatonin is a promising candidate to be further tested as an adjuvant to antitumor drugs for HCC treatment.

Non-invasive endothelial cell density measurement of in toto pre-stripped DMEK-roll - impact of pre- and intraoperative endothelial cell loss on postoperative midterm clinical outcome.

To measure the endothelial cell density (ECD) of the in toto pre-stripped endothelial Descemet membrane lamellae (EDML) and to describe the impact of pre- and intraoperative endothelial cell loss (ECL) on postoperative midterm clinical outcome. The ECD of 56 Corneoscleral Donor Discs (CDD) was first measured with an inverted specular microscope (t0pre). The measurement was then repeated non-invasively after the preparation of the EDML (t0post). DMEK was performed the next day using these grafts. Follow-up examinations took place 6 weeks, 6 months and 1 year postoperatively where the ECD was assessed. In addition, the impact of ECL 1 (during preparation) and ECL 2 (during surgery) on the ECD, visual acuity (VA) and pachymetry at 6 months and 1 year was investigated. The average ECD (in cells/mm²) at time points t0pre, t0post, 6 weeks, 6 months & 1 year was 2584 ± 200, 2355 ± 207, 1366 ± 345, 1091 ± 564 and 939 ± 352. The average logMAR VA and pachymetry (in µm) was 0.50 ± 0.27 and 597 ± 63, 0.23 ± 0.17 and 535 ± 54, 0.16 ± 0.12 and 535 ± 54, 0.06 ± 0.08 and 512 ± 37, respectively The ECL 1 (9% on average) had no significant impact on the main outcome measures after 6 months and 1 year (p > 0.11). The ECL 2 correlated significantly with the ECD and the pachymetry at 1 year postop (p < 0.02). Our results indicate that the non-invasive ECD measurement of the prestripped EDML roll before its transplantation is feasible. Despite significantly decreasing ECD up to 6 months postoperatively, visual acuity further improved and thickness further decreased up to 1 year postoperatively.

Selective Ion Transport in Two‐Dimensional Lamellar Nanochannel Membranes

AbstractPrecise and ultrafast ion sieving is highly desirable for many applications in environment‐, energy‐, and resource‐related fields. The development of a permselective lamellar membrane constructed from parallel stacked two‐dimensional (2D) nanosheets opened a new avenue for the development of next‐generation separation technology because of the unprecedented diversity of the designable interior nanochannels. In this Review, we first discuss the construction of homo‐ and heterolaminar nanoarchitectures from the starting materials to the emerging preparation strategies. We then explore the property–performance relationships, with a particular emphasis on the effects of physical structural features, chemical properties, and external environment stimuli on ion transport behavior under nanoconfinement. We also present existing and potential applications of 2D membranes in desalination, ion recovery, and energy conversion. Finally, we discuss the challenges and outline research directions in this promising field.

Selective Ion Transport in Two-Dimensional Lamellar Nanochannel Membranes.

Precise and ultrafast ion sieving is highly desirable for many applications in environment-, energy-, and resource-related fields. The development of a permselective lamellar membrane constructed from parallel stacked two-dimensional (2D) nanosheets opened a new avenue for the development of next-generation separation technology because of the unprecedented diversity of the designable interior nanochannels. In this Review, we first discuss the construction of homo- and heterolaminar nanoarchitectures from the starting materials to the emerging preparation strategies. We then explore the property-performance relationships, with a particular emphasis on the effects of physical structural features, chemical properties, and external environment stimuli on ion transport behavior under nanoconfinement. We also present existing and potential applications of 2D membranes in desalination, ion recovery, and energy conversion. Finally, we discuss the challenges and outline research directions in this promising field.

Lamellar Graphene Oxide-Based Composite Membranes for Efficient Separation of Heavy Metal Ions and Desalination of Water.

Sufficient efforts have been carried out to fabricate highly efficient graphene oxide (GO) lamellar membranes for heavy metal ion separation and desalination of water. However, selectivity for small ions remains a major problem. Herein, GO was modified by using onion extractive (OE) and a bioactive phenolic compound, i.e., quercetin. The as-prepared modified materials were fabricated into membranes and used for separation of heavy metal ions and water desalination. The GO/onion extract (GO/OE) composite membrane with a thickness of 350 nm shows an excellent rejection efficiency for several heavy metal ions such as Cr6+ (∼87.5%), As3+ (∼89.5%), Cd2+ (∼93.0%), and Pb2+ (∼99.5%) and a good water permeance of ∼460 ± 20 L m-2 h-1 bar-1. In addition, a GO/quercetin (GO/Q) composite membrane is also fabricated from quercetin for comparative studies. Quercetin is an active ingredient of onion extractives (2.1% w/w). The GO/Q composite membranes show good rejection up to ∼78.0, ∼80.5, ∼88.0, and 95.2% for Cr6+, As3+, Cd2+, and Pb2+, respectively, with a DI water permeance of ∼150 ± 10 L m-2 h-1 bar-1. Further, both membranes are used for water desalination by measuring rejection of small ions such as NaCl, Na2SO4, MgCl2, and MgSO4. The resulting membranes show >70% rejection for small ions. In addition, both membranes are used for filtration of Indus River water and the GO/Q membrane shows remarkably high separation efficiency and makes river water suitable for drinking purpose. Furthermore, the GO/QE composite membrane is highly stable up to ∼25 days under acidic, basic, and neutral environments as compared to GO/Q composite and pristine GO-based membranes.

Understanding the desalination performance of seawater passing through the lamellar BN membranes: Effect of interlayer spacing and concentration

Due to its smaller surface tension and greater wetting degree, BN-based membranes have exhibited promising application prospect in water treatment and seawater desalination. In this work, boron nitride nanosheets were employed to establish lamellar BN membranes layer by layer. By using non-equilibrium molecular dynamics simulations (NEMD), we evaluated the influence of interlayer spacing on the desalination performance of BN membranes. We also evaluated the relationship between the water permeability and the concentration of the feed solution. The simulation results showed that the water permeability of BN membrane first decreased and then increased with the interlayer spacing, it reached the minimum at the interlayer spacing of 1.1 nm, with a turning point at the same time. This is due to the strong interaction between water molecules and BN. What’s more, with the increase of the concentration of the feed solution, the hindering effect of ions on the transport of water molecules gradually decreases, the difference between water permeability in systems with different interlayer spacing decreases gradually.

Layer-by-layer repaired lamellar membrane for low stacking defect of MXene nanosheets and efficient separation performance in water purification

Two-dimensional (2D) materials have been widely considered to be used in advanced membranes for their excellent separation efficiencies. The filtration performance of lamellar membrane will be further improved after overcoming the stacking defects of 2D materials in membrane fabrication. Herein, a novel layer-by-layer repair method was proposed to fabricate MXene lamellar membranes with few defects via serial layer-by-layer compaction, crosslinking, glass rod rolling treatment and self-crosslinking. The method reduced the irregular arrangement of MXene nanosheets, repaired the wrinkled surface of every few-layer MXene nanosheets and enhanced the link between adjacent MXene nanosheets. The thickness of the layer-by-layer repaired MXene membranes was 50 nm. The layer-by-layer repaired MXene membranes possessed the rejection rates of NaCl, MgCl2 and methylene blue of 72.6%, 93.8% and 99.8% respectively associating with water flux of 5.9 L·m−2·h−1, 7.4 L·m−2·h−1 and 9.8 L·m−2·h−1 due to their regular nanochannels. They represented high stability in nanofiltration for 120 h. The swelling of MXene nanosheets was weakened in the filtration. The repair strategy is potentially applied in fabrication of other 2D lamellar membranes and their enhancement of filtration performance.

Lamellar membrane with orderly aligned glycine molecules for efficient proton conduction

Proton conduction is essential for proton exchange membrane (PEM) in hydrogen fuel cell. However, the proton conductivity of most PEMs is limited by the inferior continuity of transport channels and random arrangement of transfer carriers. Here, charged vermiculite lamellar membrane with orderly aligned glycine molecules in the interlayer channel is fabricated. We demonstrate that sulfonic acid-grafted channel induces and interacts with the end amino groups of glycine molecules, forming ordered acid-base pairs along the wall. Meantime, the carboxyl groups at the other end are located in the middle of channel, forming continuous hydrogen bond networks. Such molecule arrangement creates long-range hoping highways for proton conduction. The Vr-SO3H@Gly membrane (∼8 μm in thickness) with 10.2 wt% glycine obtains horizontal conductivity of 378.5 mS cm−1 at 90 °C and 100% RH, 2.2 times of that of commercial Nafion membrane. Moreover, the molecule arrangement is stable helped by the strong channel-glycine and glycine-glycine interactions, rendering excellent conduction stability. These then bring high hydrogen fuel cell performances with maximum current density and power density of 604 mA cm−2 and 184 mW cm−2, respectively, which are superior to Nafion and most reported 2D lamellar PEMs. This study should provide insights in developing advanced lamellar membranes for application in proton conduction field.

2D lamellar membrane with MXene hetero-intercalated small sized graphene oxide for harsh environmental wastewater treatment

Efficient wastewater treatment under harsh conditions remains a great challenge, while traditional filtration membranes are inefficient to meet the demands due to its poor chemical resistance as well as the “trade-off” effect between high permeability and selectivity. Herein, a chemical-resistant 2D lamellar membrane simultaneously with high flux and rejection for harsh environmental wastewater treatment was proposed, via assembled small sized graphene oxide nanosheets (NGO) layer-by-layer on polyphenylene sulfide (PPS) while hetero-intercalated with MXene. As the performance of 2D laminated membranes is determined by the length/tortuosity of transport channels and interlayer spacing between the flakes, NGO nanosheets were sonicated into small sizes (<500 nm) and intercalated with MXene to engineer shorter/less tortuous transport pathways while tuning the interlayer spacing for fast and selective separation. The membranes exhibit remarkably high-water permeability (up to 136.68 L·m−2·h−1·bar−1) while simultaneously with excellent retention (>99.99 %) for various dyes (molecular weight 288.77–1017.65) at the NGO/MXene ratio of 1/7, which is much higher than most reported membranes. Meanwhile, the Ti-O-C covalent bonding between NGO and MXene nanosheets also enables stable ultrafast water transmission and anti-swelling stability. The PPS-NGO/MXene membranes could still exhibit excellent separation performance even under various harsh environments (strong acids, bases, high pressures, high temperatures, bacteria, organic solvents), which holds great promise for sustainable wastewater treatment under harsh conditions.

Ultrathin Graphene Oxide-Based Nanocomposite Membranes for Water Purification.

Two-dimensional graphene oxide (GO)-based lamellar membranes have been widely developed for desalination, water purification, gas separation, and pervaporation. However, membranes with a well-organized multilayer structure and controlled pore size remain a challenge. Herein, an easy and efficient method is used to fabricate MoO2@GO and WO3@GO nanocomposite membranes with controlled structure and interlayer spacing. Such membranes show good separation for salt and heavy metal ions due to the intensive stacking interaction and electrostatic attraction. The as-prepared composite membranes showed high rejection rates (˃70%) toward small metal ions such as sodium (Na+) and magnesium (Mg2+) ions. In addition, both membranes also showed high rejection rates ˃99% for nickel (Ni2+) and lead (Pb2+) ions with good water permeability of 275 ± 10 L m-2 h-1 bar-1. We believe that our fabricated membranes will have a bright future in next generation desalination and water purification membranes.

Bis-terpyridine imprinted nanocage in the confined two-dimensional lamellar membrane for selective adsorption of Nd(III)

Nd is a strategic metal, but its extraction and separation process remains a challenging task. Here, ion-imprinted membranes with six-coordinated and semi-rigid imprinted nanocage structure were developed by self-assembling terpyridine monomers in the confined reduced graphene oxide (rGO) nanochannels. The obtained membranes displayed excellent Nd(III) adsorption capacity of 20.6 mg g−1 in the solution including seven rare earth elements (REEs), together with a 7.68 times higher selectivity to Y(III). Experimental measurements and theoretical calculations revealed that Nd(III) was well coordinated to the six pyridine-nitrogen in the nanocage, which showed shorter average coordination bond (0.77 Å) and stronger binding energy (-10.52 eV) than other REEs. These were mainly attributed to the rigid symmetrical crab-type architecture and specific cavity size of bis-terpyridine nanocage. Meanwhile, the limited decomposition of these metastable nanocage derived from 2D confined effect and nanochannel walls with few groups reduced the interference of groups at non-imprinted sites on selective adsorption. The excellent anti-swelling property of rGO framework endowed 7 static adsorption cycles and maintained high selectivity (K'(Nd/Y) > 7). Integrated into account the well-defined semi-rigid sites constituted by non-covalent interactions, this strategy provided a new idea for facile synthesis of imprinted sites with higher selectivity.

Efficient seawater desalination in lamellar nanochannel-based boridene filtration membrane.

With the progressively increasing demand for freshwater, the shortage of global freshwater resources has become one of the most serious events that all humans are facing now. The reverse osmosis (RO) technology that achieves freshwater from seawater is a promising strategy. However, current RO membranes suffer from the bottleneck of low efficiency. In this work, we designed a RO membrane based on a novel two-dimensional nanomaterial, boridene, prepared by stacking them into lamellar nanochannels. We employed the molecular dynamics (MD) simulation approach to investigate the desalination performance of the designed boridene lamellar membrane. Our results showed that the water permeability through the boridene membrane increased following the incremental interlayer spacing. In addition, the boridene membrane exhibits high water permeability and ideal salt rejection, featuring water permeability far beyond those obtained from commercial RO membranes with two orders of magnitude enhancement. Further free energy calculations demonstrated that the water molecules are energetically more favorable to transport through the boridene lamellar nanochannels than ions. Therefore, our results highlight that the boridene lamellar nanochannel-based filtration membrane can be utilized as a potential outstanding candidate in RO membranes for future desalination applications.

Covalent organic framework-based lamellar membranes for water desalination applications

This review summarizes the current fabrication methods of COF-based lamellar membranes, and discusses their application in water desalination.

Application of lamellar nickel hydroxide membrane as a tunable platform for ionic thermoelectric studies.

The recent trend in thermoelectric literature suggests that ionic thermoelectric (i-TE) materials are ideal for directly converting low-grade waste heat into electricity. Here, we developed a unique platform for i-TE studies by stacking two-dimensional sheets of β-Ni(OH)2 prepared by a bottom-up method. The lamellar membrane of β-Ni(OH)2 (Ni-M) itself does not display significant thermovoltages, but when doped with mobile anion-generating species (like aminopropyl functionalized magnesium phyllosilicate or organic halide salts), it exhibits significant negative Seebeck coefficient (up to -13.7 ± 0.2 mV K-1). Similarly, upon doping with cation-generating species like poly(4-styrene sulfonic acid) (PSS), it displays positive Seebeck coefficient values (up to +12 ± 1.9 mV K-1). The positive and negative i-TE materials prepared by doping Ni-M are assembled into ionic thermopiles capable of generating thermovoltages up to 1 V, at ΔT = 12 K. The Ni-M-based nanofluidic systems demonstrated an additional path of electricity harvesting by connecting colder zones of the positive and negative i-TE materials with other ion conducting membranes. In contrast to organic polymer-based i-TE systems, the Ni-M based system exhibited consistent performance despite being exposed to high temperatures (∼200 °C, 5 minutes).

Functionalized graphene oxide-based lamellar membranes for organic solvent nanofiltration applications.

In this study, two-dimensional graphene oxide-based novel membranes were fabricated by modifying the surface of graphene oxide nanosheets with six-armed poly(ethylene glycol) (PEG) at room conditions. The as-modified PEGylated graphene oxide (PGO) membranes with unique layered structures and large interlayer spacing (∼1.12 nm) were utilized for organic solvent nanofiltration applications. The as-prepared 350 nm-thick PGO membrane offers a superior separation (>99%) against evans blue, methylene blue and rhodamine B dyes along with high methanol permeance ∼ 155 ± 10 L m-2 h-1, which is 10-100 times high compared to pristine GO membranes. Additionally, these membranes are stable for up to 20 days in organic solvent. Hence the results suggested that the as-synthesized PGO membranes with superior separation efficiency for dye molecules in organic solvent can be used in future for organic solvent nanofiltration application.

Incorporation of atomically dispersed cobalt in the 2D metal–organic framework of a lamellar membrane for highly efficient peroxymonosulfate activation

The peroxymonosulfate (PMS)-based Fenton-like reaction is one of the most promising technologies for controlling emerging organic pollutants in water and wastewater. Herein, we present a novel lamellar membrane comprised of a water-stable two-dimensional (2D) porphyrin metal–organic framework with atomically dispersed CoN4 catalytic centers (CoSA-PMOF) for highly efficient PMS activation. The single Co atoms decorating the porphyrin rings of CoSA-PMOF boosted PMS activation and, subsequently, SO4•− radical generation. CoSA-PMOF enhanced the degradation rate of moxifloxacin (MOX) in water by more than 20 times compared with the pristine PMOF. The novel 2D CoSA-PMOF lamellar membrane achieved an exceptional performance, with 100 % MOX removal via single-pass filtration at a high flux of 48 L m-2 h-1. Its excellent catalytic performance may be attributed to the confinement effect that traps PMS and pollutant molecules in the vicinity of the single-atom Co sites within the lamellar membrane during filtration.

Significant enhancement in hydrogen evolution rate of 2D bismuth oxychloride lamellar membrane photocatalyst with cellulose nanofibers

Photocatalytic hydrogen evolution (PHE) is a sustainable alternative for generating green and clean energy. However, it requires the use of nanoscale photocatalysts, whose applicability is limited by their poor reusability and proton release from water molecules. Herein, a porous two-dimensional lamellar membrane (2DLM) photocatalyst was fabricated from bismuth oxychloride (BiOCl) nanosheets (BNs) and cellulose nanofibers (CNFs) via layer-by-layer self-assembly. The hybridization of the CNFs with the BNs improved the PHE rate of the resulting BiOCl/CNFs membrane (BCM). The optimal PHE rate was observed for a CNF content of 3.2 wt% and was 4.7-times that of raw BNs dispersed in an aqueous solution alone and 1.85-times that of the BiOCl membrane (BM). Moreover, the PHE rate remained unchanged even after 10 discontinuous cycles for a total time of 60 h. Comprehensive experimental characterization and molecular dynamics simulations confirmed that the introduction of the CNFs effectively regulated the hydrogen bond network of the confined water molecules, thus improving the efficiency of the conversion of H2O into H2. Meanwhile, the optimization of the nanochannel sizes of the BNs by the hybridized CNFs accelerated water transport within the nanochannels. The 2DLM also showed excellent mechanical strength, flexibility, and translucence. This strategy of fabricating 2DLMs using a nanosheet photocatalyst and CNFs not only results in improved PHE performance but also should also aid the development of stable and reusable photocatalysts for other industrial applications.

Bioinspired Macrocyclic Molecule Supported Two-Dimensional Lamellar Membrane with Robust Interlayer Structure for High-Efficiency Nanofiltration.

2D lamellar membranes (2DLMs) are used for efficient desalination and nanofiltration. However, weak interactions between adjacent stacked nanosheets result in susceptibility to swelling that limits practical applicability. Inspired by the super adhesion of multi-point suction cups on octopus tentacles, a 2DLM is constructed from Ti3 C2 Tx MXene supported by the macrocyclic "multi-point" molecule cucurbit[5]uril (CB5) and demonstrated for nanofiltration of methyl blue (MB) and enrichment of uranyl carbonate. Experimental results and density functional theory calculations indicate that CB5 rivets to the surface of the nanoflakes through strong stable interactions between its multiple binding sites and surface hydroxyl functional groups on MXene nanosheets. This novel 2DLM exhibits excellent nanofiltration performance (69 L m-2 h-1 bar-1 permeance with 93.6% rejection for MB) and can be recycled at least 30 times without significant degradation. The 2DLM exhibits excellent swelling resistance at high salinity, with a demonstration of selective enrichment of uranyl carbonate from artificial water and natural seawater. The results provide a new strategy for constructing highly stable 2DLMs with interlayer spacing controllable from sub-nano to nanometer scales, for size-selective sieving of molecules and ions, high-efficiency nanofiltration, and other applications.

Molecular dissolution behaviors on porous membrane surface using hierarchical metal–organic framework lamellar membrane

AbstractLamellar membranes, especially assembled by microporous framework nanosheets, have excited interest for fast molecular permeation. However, the underlying molecular dissolution behaviors on membrane surface, especially at pore entrances, remain unclear. Here, hierarchical metal–organic framework (MOF) lamellar membranes with 7 nm‐thick surface layer and 553 nm‐thick support layer are prepared. Hydrophilic (–NH2) or hydrophobic (–CH3) groups are decorated at pore entrances on surface layer to manipulate wettability, while –CH3 groups on support layer provide comparable, low‐resistance paths. We demonstrate that molecular dissolution behaviors are determined by molecule–molecule and molecule–pore interactions, derived from intrinsic parameters of molecule and membrane. Importantly, two dissolution model equations are established: for hydrophobic membrane surface, dissolution activation energy (ES) obeys ES = Kmln[(γL‐γC)μd2], while turns to ES=Kaln[(γL‐γC)δeμd2] for hydrophilic one. Particularly, hydrophilic pore entrances exert strong interaction with polar molecules, thus compensating the energy consumed by molecule rearrangement, giving fast permeation (&gt;270 L m−2 h−1 bar−1).