Electrochemical-repaired porous graphene membranes for precise ion-ion separation.

The preparation of atom-thick porous lattice hosting Å-scale pores is attractive to achieve a large ion-ion selectivity in combination with a large ion flux. Graphene film is an ideal selective layer for this if high-precision pores can be incorporated, however, it is challenging to avoid larger non-selective pores at the tail-end of the pore size distribution which reduces ion-ion selectivity. Herein, we develop a strategy to overcome this challenge using an electrochemical repair strategy that successfully masks larger pores in large-area graphene. 10-nm-thick electropolymerized conjugated microporous polymer (CMP) layer is successfully deposited on graphene, thanks to a strong π-π interaction in these two materials. While the CMP layer itself is not selective, it effectively masks graphene pores, leading to a large Li+/Mg2+ selectivity from zero-dimensional pores reaching 300 with a high Li+ ion permeation rate surpassing the performance of reported materials for ion-ion separation. Overall, this scalable repair strategy enables the fabrication of monolayer graphene membranes with customizable pore sizes, limiting the contribution of nonselective pores, and offering graphene membranes a versatile platform for a broad spectrum of challenging separations.

Internal Concentration Polarization in the Polyamide Active Layer of Thin-Film Composite Membranes.

A free-standing polyamide (PA) film is fabricated via in situ release from a thin-film composite (TFC) membrane achieved through the removal of the polysulfone support. The structure parameter S of the PA film is measured to be 24.2 ± 12.6 µm, which is about 87-fold of its film thickness. A significant decline in water flux of the PA film from an ideal forward osmosis membrane is observed. We find that the decline is predominantly influenced by the internal concentration polarization (ICP) of the PA film based on our experimental measurements and theoretical calculations. We propose that the asymmetric hollow structures of the PA layer with dense crusts and cavities may be the underlying cause of the occurrence of the ICP. More importantly, the structure parameter of the PA film can be reduced and its ICP effect can be mitigated by tuning its structures with fewer and shorter cavities. Our results for the first time provide experimental evidence to prove that the PA layer of the TFC membrane has the ICP effect, which could potentially provide fundamental insights into the influence of structural properties of PA on the membrane separation performance.

An Ionic Diode Covalent Organic Framework Membrane for Efficient Osmotic Energy Conversion.

Heterogeneous membranes that exhibit an ionic diode effect are promising candidates for osmotic energy conversion. However, existing heterogeneous membranes lack molecular-level designed ion channels, thereby limiting their power densities. Here, we demonstrate ionic diode covalent organic framework (COF) membranes with well-defined ion channels, asymmetric geometry and surface charge polarity as high-performance osmotic power generators. The COF diode membranes are comprised of heterojunctions combining a positively charged ultrathin COF layer and a negatively charged COF layer supported by a porous COF nanofiber scaffold, exhibiting an ionic diode effect that effectuates fast unidirectional ion diffusion and anion selectivity. Density functional theory calculations reveal that the differentiated interactions between anions and COF channels contributed to superior I- transport over other anions. Consequently, the COF diode membranes achieved high output power densities of 19.2 and 210.1 W m-2 under a 50-fold NaCl and NaI gradient, respectively, outperforming state-of-the-art heterogeneous membranes. This work suggests the great potential of COF diode membranes for anion transport and energy-related applications.

Conjugated microporous polymer membranes for light-gated ion transport.

Inspired by the light-gated ion channels in cell membranes that play important roles in many biological activities, herein, we developed an artificial light-gated ion channel membrane out of conjugated microporous polymers. Through bottom-up design of the monomer molecular structure and by the electropolymerization method, the membrane pore size and thickness were precisely controlled on the molecular level. The obtained membrane exhibited uniform pore size and highly sensitive light-switchable response. The photoisomerization of the polymer chain resulted in a reversible "on and off" light control over the pore size and subsequently led to light-gated ion transport across the membrane for a series of ions including hydrogen, potassium, sodium, lithium, calcium, magnesium, and aluminum ions.

Giant Osmotic Energy Conversion through Vertical-Aligned Ion-Permselective Nanochannels in Covalent Organic Framework Membranes.

Nanofluidic membranes have been demonstrated as promising candidates for osmotic energy harvesting. However, it remains a long-standing challenge to fabricate high-efficiency ion-permselective membranes with well-defined channel architectures. Here, we demonstrate high-performance osmotic energy conversion membranes based on oriented two-dimensional covalent organic frameworks (COFs) with ultrashort vertically aligned nanofluidic channels that enabled efficient and selective ion transport. Experiments combined with molecular dynamics simulations revealed that exquisite control over channel orientation, charge polarity, and charge density contributed to high ion selectivity and permeability. When applied to osmotic energy conversion, a pair of 100 nm thick oppositely charged COF membranes achieved an ultrahigh output power density of 43.2 W m-2 at a 50-fold salinity gradient and up to 228.9 W m-2 for the Dead Sea and river water system. The achieved power density outperforms the state-of-the-art nanofluidic membranes, suggesting the great potential of oriented COF membranes in the fields of advanced membrane technology and energy conversion.

Carbon nanotube supported oriented metal organic framework membrane for effective ethylene/ethane separation.

Zeolitic imidazolate framework 8 (ZIF-8) is effective for C3H6/C3H8 separation because of the "sieving effect" of a six-membered (6-M) window. Here, we demonstrate that ZIF-8 is a versatile material that could effectively separate C2H4 from C2H6 via its 4-M window along the <100> direction. We established a facile and environmentally friendly carbon nanotube (CNT)-induced oriented membrane (CNT-OM) approach to fabricate a {100}-oriented ZIF-8 membrane (100-M). In this approach, 2-methyimidazole was anchored onto the CNT surface followed by 3-hour in situ growth in aqueous solution at room temperature. The obtained 100-M, whose 4-M window is aligned along the transport pathway, showed ~3 times higher C2H4/C2H6 selectivity than a randomly oriented membrane. Thus, this work demonstrates that the membrane orientation plays an important role in tuning selectivity toward different gas pairs. Furthermore, 100-M exhibited excellent mechanical stability that could sustain the separation performance after bending at a curvature of ~109 m-1.

An Ultrahigh-Flux Nanoporous Graphene Membrane for Sustainable Seawater Desalination using Low-Grade Heat.

Membrane distillation has attracted great attention in the development of sustainable desalination and zero-discharge processes because of its possibility of recovering 100% water and the potential for integration with low-grade heat, such as solar energy. However, the conventional membrane structures and materials afford limited flux thus obstructing its practical application. Here, ultrathin nanoporous graphene membranes are reported by selectively forming thin graphene layers on the top edges of a highly porous anodic alumina oxide support, which creates short and fast transport pathways for water vapor but not liquid. The process avoids the challenging pore-generation and substrate-transfer processes required to prepare regular graphene membranes. In the direct-contact membrane distillation mode under a mild temperature pair of 65/25 °C, the nanoporous graphene membranes show an average water flux of 421.7 L m-2 h-1 with over 99.8% salt rejection, which is an order of magnitude higher than any reported polymeric membranes. The mechanism for high water flux is revealed by detailed characterizations and theoretical modeling. Outdoor field tests using water from the Red Sea heated under direct sunlight radiation show that the membranes have an average water flux of 86.3 L m-2 h-1 from 8 am to 8 pm, showing a great potential for real applications in seawater desalination.

Oriented Two-Dimensional Covalent Organic Framework Membranes with High Ion Flux and Smart Gating Nanofluidic Transport.

Nanofluidic ion transport holds high promise in bio-sensing and energy conversion applications. However, smart nanofluidic devices with high ion flux and modulable ion transport capabilities remain to be realised. Herein, we demonstrate smart nanofluidic devices based on oriented two-dimensional covalent organic framework (2D COF) membranes with vertically aligned nanochannel arrays that achieved a 2-3 orders of magnitude higher ion flux compared with that of conventional single-channel nanofluidic devices. The surface-charge-governed ion conductance is dominant for electrolyte concentration up to 0.01 M. Moreover, owing to the customisable pH-responsivity of imine and phenol hydroxyl groups, the COF-DT membranes attained an actively modulable ion transport with a high pH-gating on/off ratio of ≈100. The customisable structure and rich chemistry of COF materials will offer a promising platform for manufacturing nanofluidic devices with modifiable ion/molecular transport features.

Precise Sub-Angstrom Ion Separation Using Conjugated Microporous Polymer Membranes.

Polymer membranes typically possess a broad pore-size distribution that leads to much lower selectivity in ion separation when compared to membranes made of crystalline porous materials; however, they are highly desirable because of their easy processability and low cost. Herein, we demonstrate the fabrication of ion-sieving membranes based on a polycarbazole-type conjugated microporous polymer using an easy to scale-up electropolymerization strategy. The membranes exhibited high uniform sub-nanometer pores and a precisely tunable membrane thickness, yielding a high ion-sieving performance with a sub-1 Å size precision. Both experimental results and molecular simulations suggested that the impressive ion-sieving performance of the CMP membranes originates from their uniform and narrow pore-size distribution.

Electropolymerization of robust conjugated microporous polymer membranes for rapid solvent transport and narrow molecular sieving.

Pore size uniformity is one of the most critical parameters in determining membrane separation performance. Recently, a novel type of conjugated microporous polymers (CMPs) has shown uniform pore size and high porosity. However, their brittle nature has prevented them from preparing robust membranes. Inspired by the skin-core architecture of spider silk that offers both high strength and high ductility, herein we report an electropolymerization process to prepare a CMP membrane from a rigid carbazole monomer, 2,2',7,7'-tetra(carbazol-9-yl)-9,9'-spirobifluorene, inside a robust carbon nanotube scaffold. The obtained membranes showed superior mechanical strength and ductility, high surface area, and uniform pore size of approximately 1 nm. The superfast solvent transport and excellent molecular sieving well surpass the performance of most reported polymer membranes. Our method makes it possible to use rigid CMPs membranes in pressure-driven membrane processes, providing potential applications for this important category of polymer materials.

Tuning the Surface Structure of Polyamide Membranes Using Porous Carbon Nitride Nanoparticles for High-Performance Seawater Desalination.

Enhancing the water flux while maintaining the high salt rejection of existing reverse osmosis membranes remains a considerable challenge. Herein, we report the use of a porous carbon nitride (C3N4) nanoparticle to potentially improve both the water flux and salt rejection of the state-of-the-art polyamide (PA) thin film composite (TFC) membranes. The organic-organic covalent bonds endowed C3N4 with great compatibility with the PA layer, which positively influenced the customization of interfacial polymerization (IP). Benefitting from the positive effects of C3N4, a more hydrophilic, more crumpled thin film nanocomposite (TFN) membrane with a larger surface area, and an increased cross-linking degree of PA layer was achieved. Moreover, the uniform porous structure of the C3N4 embedded in the "ridge" sections of the PA layer potentially provided additional water channels. All these factors combined provided unprecedented performance for seawater desalination among all the PA-TFC membranes reported thus far. The water permeance of the optimized TFN membrane is 2.1-folds higher than that of the pristine PA-TFC membrane, while the NaCl rejection increased to 99.5% from 98.0%. Our method provided a promising way to improve the performance of the state-of-art PA-TFC membranes in seawater desalination.

New Insights into the Role of an Interlayer for the Fabrication of Highly Selective and Permeable Thin-Film Composite Nanofiltration Membrane.

A triple-layered TFC nanofiltration (NF) membrane consisting of a polyamide (PA) top layer covered on a poly(ether sulfone) microfiltration membrane with a carbon nanotube (CNT) interlayer was fabricated via interfacial polymerization. The structure and properties of the PA active layer could be finely tailored by tuning the interfacial properties and pore structure of the CNT interlayer, including its surface pore size and thickness, thus improving its NF performance. This TFC NF membrane exhibited a high divalent salt rejection (the rejection of Na2SO4 and MgSO4 solution >98.3%) and dye rejection (the rejection of methyl violet (MV) >99.5%) with a high pure water flux of around 21 L m-2 h-1 bar-1. Excitingly, this membrane also showed excellent selectivity to both mono/divalent salt ion (the selectivity of Cl-/SO42- is as high as 85.5) and NaCl/dye solution (the selectivity of NaCl/MV is more than 123.5), which are much higher than most of other commercial and reported NF membranes. Moreover, this membrane also showed a good separation performance and long-term stability during a continuous NF process for a salt/dye mixture solution. This triple-layered TFC NF membrane showed a great promise for applications in both wastewater treatment and dyes recycling.

Surface-independent one-pot chelation of copper ions onto filtration membranes to provide antibacterial properties.

A one-pot method was developed for the chelation of copper ions onto the surface of filtration membrane to provide antibacterial properties. This simple, universal and cost-effective dopamine-Cu2+ approach provides a method of mitigating the long-term biofouling of surfaces.

PINK1 triggers autocatalytic activation of Parkin to specify cell fate decisions.

BACKGROUND: The PINK1-Parkin pathway is known to play important roles in regulating mitochondria dynamics, motility, and quality control. Activation of this pathway can be triggered by a variety of cellular stress signals that cause mitochondrial damage. How this pathway senses different levels of mitochondrial damage and mediates cell fate decisions accordingly is incompletely understood. RESULTS: Here, we present evidence that PINK1-Parkin has both cytoprotective and proapoptotic functions. PINK1-Parkin operates as a molecular switch to dictate cell fate decisions in response to different cellular stressors. Cells exposed to severe and irreparable mitochondrial damage agents such as valinomycin can undergo PINK1-Parkin-dependent apoptosis. The proapoptotic response elicited by valinomycin is associated with the degradation of Mcl-1. PINK1 directly phosphorylates Parkin at Ser65 of its Ubl domain and triggers activation of its E3 ligase activity through an autocatalytic mechanism that amplifies its E3 ligase activity toward Mcl-1. CONCLUSIONS: Autocatalytic activation of Parkin bolsters its accumulation on mitochondria and apoptotic response to valinomycin. Our results suggest that PINK1-Parkin constitutes a damage-gated molecular switch that governs cellular-context-specific cell fate decisions in response to variable stress stimuli.

[Oct4 methylation in induced differentiation of bone mesenchymal stem cells].

OBJECTIVE: To investigate the methylation Oct4 in orientation induced differentiation in bone marrow mesenchymal stem cells METHODS: Mice BMSCs were isolated and purified from bone marrow by adherent culture,and then identified by morphology and immunocytochemistry.Mouse osteoblastic cells were cultured by bone fragments inoculation,and then identified by alkaline phosphatase(AKP)staining and alizarin red staining.BMSCs were induced to differentiate into osteoblasts in vitro. Indirect immunofluorescence staining and reverse transcription polymerase chain reaction(RT PCR)were used to detect the expressions of Oct4 in BMSCs before and after induction.The methylation status of Oct4 gene in mouse BMSCs was explored by a methylation specific PCR before and after induction RESULTS: The isolated mice BMSCs massively proliferated in vitro and formed cell colones with uniform morphology.Positive expressions of CD29,cKit,and CD44 and negative expression of CD34 were found in the isolated cells.After 10 days[DK]'[DK] induction,both AKP and the alizarin red were positive in cells and osteoblastic cells isolated from mice skull bones.The indirect immunoinfluorescence staining and RT-PCR also showed that the Oct4 expression in the directed differentiation of mouse BMSCs was down-regulated.The CpG island of Otc4 gene promoter in mouse BMSCs became methylated during the induced differentiation. CONCLUSIONS: Mice BMSCs and osteoblasts were successfully cultured in vitro in this studyOct4 may be involved in the maintenance of adult stem cell pluripotency.The down regulated expression of Oct4 gene in mouse BMSCs during the directed differentiation may contribute to the methylation of CpG island in Otc4 gene promoter.

[Expression of osteopontin in the pericystic layer of hepatic hydatid cyst].

OBJECTIVE: To investigate the expression and distribution of osteopontin (OPN) in the pericystic layer of Echinococcus granulosus cyst. METHODS: 60 surgically excised cysts were studied with HE and immunohistochemistry staining by using antibodies specific for OPN. Immunofluorescence double labeling technique and Media Cybernetics Image (Pro Plus 5.1 software) were used to appraise the relationship between the OPN and macrophages (CD68). RESULTS: Expression of OPN was found at various degree in hydatid cysts, 75% (45/60) was distributed in the intra-layer at the parasite side, 8.3% (5/60) distributed in the extra-layer near the side of liver parenchyma ("exocyst"-layer vs "adventitia"-layer, P<0.01). Macrophages were identified between the intra-layer and extra-layer, and OPN was observed in most of the macrophages. Meanwhile, OPN was concurrently found with the deposit of calcium in a similar distribution in the hydatid cyst. CONCLUSION: Osteopontin mainly distributes in the intra-pericystic layer of hepatic hydatid cyst.

Expression of germ cell nuclear factor in mouse germ cells and sperm during postnatal period.

AIM: To assess the spatial and temporal expression of germ cell nuclear factor (GCNF) in male mouse germ cells during postnatal development and in sperm before and after capacitation. METHODS: The indirect immunofluorescence method with anti-GCNF antiserum was used to investigate the GCNF expression in mice at day 8, 10, 14, 17, 20, 28, 35, 70, and 420 after birth and in sperm before and after capacitation. RESULTS: With the proceeding of spermatogenesis, GCNF was first detected in the nuclei of spermatogonia and a few early stage primary spermatocytes at day 8, which was increased gradually at day 10 to 14 inclusive. From day 17 to day 20, the GCNF was concentrated in round spermatids, while both spermatogonia and early stage primary spermatocytes became GCNF negative. From day 28 until day 420, strong GCNF expression was shown in round spermatids and pachytene spermatocytes, while spermatogonia, early primary spermatocytes and elongating spermatids were all GCNF negative. In addition, it was also found that GCNF was localized on the acrosomal cap region of spermatozoa and there was a big change in GCNF expression during capacitation, from 98 % GCNF positive before capacitation to about 20 % positive following capacitation. The localization of GCNF in caput and cauda spermatozoa was similar. CONCLUSION: GCNF may play important roles in spermatogenesis, capacitation and fertilization.

Spatial and temporal expression of germ cell nuclear factor in murine epididymis.

AIM: To investigate the spatial and temporal expression of germ cell nuclear factor (GCNF) in mouse and rat epididymis during postnatal period. METHODS: The epididymal sections from different postnatal days were stained for GCNF by the indirect immunofluorescence technique and digital photographs were taken by a Carl Zeiss confocal microscope. RESULTS: GCNF was first detected on day 12 in mouse epididymis and day 14 in rat epididymis. The highest expression of GCNF was observed on day 35 in both mouse and rat epididymis. In adults, GCNF exhibited a region-specific expression pattern, i.e., it was expressed predominantly in the initial segment, caput and proximal corpus of rat epididymis and was abundant in the proximal corpus of mouse epididymis. GCNF could be found in the nuclei of the principal, apical, narrow, clear and halo cells. CONCLUSION: GCNF may play an important role in epididymal differentiation and development and in sperm maturation.

Androgen down-regulated and region-specific expression of germ cell nuclear factor in mouse epididymis.

Germ cell nuclear factor (GCNF), a nuclear orphan receptor, involved in spermatogenesis, neurogenesis, differentiation, and embryo development, was highly expressed with two transcripts (7.4 and 2.3 kb) in mouse testis and with only one transcript (7.4 kb) slightly expressed in brain, liver, and kidney. The 2.3-kb transcript was restricted to round spermatids at stages VII and VIII of the spermatogenic cycle. The present report demonstrated its expression in epididymis as well, but at a very low level. Northern blot analysis showed two transcripts: a common 7.4-kb transcript and a unique 3.1-kb transcript. The expression levels of both GCNF transcripts in epididymis were down-regulated by androgen, as observed in castrated animals and aged mice. Polyclonal antisera against GCNF protein were raised. Western blot analysis showed the presence of only one band in total protein extracts from either mouse testis or epididymis. It indicated that the two mRNAs (7.4 and 3.1 kb) encode for the same protein as in testis. Fluorescent immunohistochemical staining and in situ hybridization showed that its expression was in the principal cell abundant in the corpus region. It implies that some androgen-regulated gene expressions located at the corpus principal cells might be controlled by GCNF.