Nanowire-assisted electrochemical perforation of graphene oxide nanosheets for molecular separation.

Two-dimensional nanosheets, e.g., graphene oxide (GO), have been widely used to fabricate efficient membranes for molecular separation. However, because of poor transport across nanosheets and high width-to-thickness ratio, the permeation pathway length and tortuosity of these membranes are extremely large, which limit their separation performance. Here we report a facile, scalable, and controllable nanowire electrochemical concept for perforating and modifying nanosheets to shorten permeation pathway and adjust transport property. It is found that confinement effects with locally enhanced charge density, electric field, and hydroxyl radical generation over nanowire tips on anode can be executed under low voltage, thereby inducing confined direct electron loss and indirect oxidation to reform configuration and composition of GO nanosheets. We demonstrate that the porous GO nanosheets with a lot of holes are suitable for assembling separation membranes with tuned accessibility, tortuosity, interlayer space, electronegativity, and hydrophilicity. For molecular separation, the prepared membranes exhibit quadruple water permeance and higher rejections for salts (>91%) and small molecules (>96%) as/than original ones. This nanowire electrochemical perforation concept offers a feasible strategy to reconstruct two-dimensional materials and tune their transport property for separation.

Fine-Tuned Active Layer Morphology for Bulk Heterojunction Organic Solar Cells with Indene-C60 Bisadduct as a Third Component.

Active layer morphology is of vital importance for the photovoltaic performance of organic solar cells (OSCs). As fullerene derivatives and nonfullerene acceptors are highly complementary in many aspects, fullerene derivatives as a third component in nonfullerene OSCs could tune the blend morphology and improve the power conversion efficiency (PCE). Relative to PCBM, the indene-C60 bisadduct (IC60BA) as the third component in nonfullerene binary OSCs has not been extensively studied. Here, the fullerene derivative IC60BA is introduced into the PTZ1:IDIC blend system to finely tune the active layer morphology. Although the addition of IC60BA reduced the film absorption in the visible region and weakened the crystallinity, the more symmetric charge transport property, smaller domain size, and higher domain purity led to improved photovoltaic performance. This study indicates that IC60BA is a promising candidate to finely tune the morphology for achieving highly efficient OSCs.

Mechanical compression management of the right middle cerebral artery inferior trunk using a stent during coil embolization of middle cerebral artery aneurysms: A case report and literature review.

Endovascular coil embolization is a minimally invasive, rapid, and effective method for the treatment of intracranial aneurysms. However, complications associated with coil embolization, such as intraoperative aneurysm rupture or arterial occlusion, should be promptly managed during the procedure to avoid catastrophic consequences. This study presents a case of mechanical compression management of the right middle cerebral artery (MCA) inferior trunk during coil embolization for bilateral MCA aneurysms. The inferior trunk of the right MCA was abruptly occluded due to mechanical compression during coil embolization of the right MCA bifurcation aneurysm. A Solitaire AB stent (4 â€‹× â€‹20 mm, Covidien/Medtronic, Dublin, Ireland) was implanted in the inferior trunk of the right MCA after tirofiban was injected via a microcatheter, and the right inferior trunk was recanalized. The patient also underwent coil embolization of the left MCA bifurcation aneurysm, without any complications. It is crucial to recognize compressive occlusion of adjacent aneurysm branches to avoid severe complications during intracranial aneurysm embolization. Stent placement is a rescue treatment option for recanalization of an occluded artery.

Fast Blood Oxygenation through Hemocompatible Asymmetric Polymer of Intrinsic Microporosity Membranes.

Membrane technology has attracted considerable attention for chemical and medical applications, among others. Artificial organs play important roles in medical science. A membrane oxygenator, also known as artificial lung, can replenish O2 and remove CO2 of blood to maintain the metabolism of patients with cardiopulmonary failure. However, the membrane, a key component, is subjected to inferior gas transport property, leakage propensity, and insufficient hemocompatibility. In this study, we report efficient blood oxygenation by using an asymmetric nanoporous membrane that is fabricated using the classic nonsolvent-induced phase separation method for polymer of intrinsic microporosity-1. The intrinsic superhydrophobic nanopores and asymmetric configuration endow the membrane with water impermeability and gas ultrapermeability, up to 3,500 and 1,100 gas permeation units for CO2 and O2, respectively. Moreover, the rational hydrophobic-hydrophilic nature, electronegativity, and smoothness of the surface enable the substantially restricted protein adsorption, platelet adhesion and activation, hemolysis, and thrombosis for the membrane. Importantly, during blood oxygenation, the asymmetric nanoporous membrane shows no thrombus formation and plasma leakage and exhibits fast O2 and CO2 transport processes with exchange rates of 20 to 60 and 100 to 350 ml m-2 min-1, respectively, which are 2 to 6 times higher than those of conventional membranes. The concepts reported here offer an alternative route to fabricate high-performance membranes and expand the possibilities of nanoporous materials for membrane-based artificial organs.

Hetero-Polycrystalline Membranes with Narrow and Rigid Pores for Molecular Sieving.

Molecular sieving membranes have great potential for energy-saving separations, but they suffer from permeability-selectivity trade-off limitation. In this report, simultaneous hetero-crystallization and hetero-linker coordination of metal-organic framework (MOF) hollow fiber membranes through one-pot synthesis for precise gas separation is reported. It is found that the hetero-polycrystalline membranes consist of 2D and 3D MOF phases and are defect-free and roughly orientated, hetero-linker exchange of 3D phase by larger geometric ones can narrow transport pathway, and framework rigidification occurs and thus fixes MOF channels. The prepared membranes are robust and reproducible, and exhibit substantially improved performance, with H2 /CO2 , H2 /N2 , and H2 /CH4 selectivities up to 361, 482, and 541, respectively, accompanied by high H2 permeance over 1100 gas permeation units, which can easily outclass trade-off upper bounds of state-of-the-art membranes.

Self-assembly of stable and high-performance molecular cage-crosslinked graphene oxide membranes for contaminant removal.

Membrane separation is regarded as efficient technology to alleviate global water crisis. Two-dimensional membranes are promising for contaminant removal from wastewaters, but their uncontrollable transport pathway and instability hinder the further development. In this study, the high-performance and stable two-dimensional framework membranes are self-assembled by graphene oxide (GO) nanosheets and amino-appended metal-organic polyhedrons (MOPs) for water purification and remediation. The MOP molecular cages are uniformly intercalated between GO nanosheets and enriched at defects/edges, and can crosslink membranes, to provide in-plane selective channels, refine vertical passageways, and fix out-of-plane interlayer spaces. The prepared GO/MOP framework membranes have improved stability and nanofiltration performance under cross-flow condition, can keep performance in water after 50 h filtration, and show high rejections over 92% for Na2SO4 and 99% for antibiotic and dye contaminants with molecular weights over 280 g mol-1, and sixfold permeance as that of GO membranes. Our molecular cage-intercalated and crosslinked two-dimensional frameworks offer an alternative route to design robust membranes for efficient removal of contaminants in wastewaters.

Surface-catalyzed electro-Fenton with flexible nanocatalyst for removal of plasticizers from secondary wastewater effluent.

Activation of H2O2 with metal-free catalysts is an efficient and environmentally benign alternative to electron-Fenton (EF) for organics degradation. In the present study, flexible nanocatalysts were synthesized with self-regulated metal oxide nanoparticles (FeOx NPs) for efficient removal of plasticizers from secondary wastewater effluent (SWE). Compared with NGr/EF and FeOx@Gr/EF systems, FeOx@NGr/EF could enhance the decay kinetics of plasticizers by 3.9-4.4 times and reduce 48-59% of the disposal cost. Reactive oxygen species tests and trapping experiments proved that the surface-catalyzed EF effectively broadened the range of solution pH. Density functional theory calculations coupled with electrochemical measurements indicated that the electron transfer rates between Fe-O-C atoms were enhanced with N-doping due to strong interactions between N-Fe bond. The synergistic effects of FeOx and N could improve the oxygen reduction activity for H2O2 generation, and accelerate electron transfer between FeOx/NGr and H2O2 for •OH generation, offering an alternative for wastewater treatment.

Vapor-Phase Processing of Metal-Organic Frameworks.

ConspectusPorous metal-organic frameworks (MOFs), formed from organic linkers and metal nodes, have attracted intense research attention. Because of their high specific surface areas, uniform and adjustable pore sizes, and versatile physicochemical properties, MOFs have shown disruptive potential in adsorption, catalysis, separation, etc. For many of these applications, MOFs are synthesized solvothermally as bulk powders and subsequently shaped as pellets or extrudates. Other applications, such as membrane separations and (opto)electronics, require the implementation of MOFs as (patterned) thin films. Most thin-film formation methods are adapted from liquid-phase synthesis protocols. Precursor transport and nucleation are difficult to control in these cases, often leading to particle formation in solution. Moreover, the use of solvents gives rise to environmental and safety challenges, incompatibility issues with some substrates, and corrosion issues in the case of dissolved metal salts. In contrast, vapor-phase processing methods have the merits of environmental friendliness, control over thickness and conformality, scalability in production, and high compatibility with other workflows.In this Account, we outline some of our efforts and related studies in the development and application of vapor-phase processing of crystalline MOF materials (MOF-VPP). We first highlight the advances and mechanisms in the vapor-phase deposition of MOFs (MOF-VPD), mainly focusing on the reactions between a linker vapor and a metal-containing precursor layer. The characteristics of the obtained MOFs (thickness, porosity, crystallographic phase, orientation, etc.) and the correlation of these properties with the deposition parameters (precursors, temperatures, humidity, post-treatments, etc.) are discussed. Some in situ characterization methods that contributed to a fundamental understanding of the involved mechanisms are included in the discussion. Second, four vapor-phase postsynthetic functionalization (PSF) methods are summarized: linker exchange, guest loading, linker grafting, and metalation. These approaches eliminate potential solubility issues and enable fast diffusion of reactants and guests as well as a high loading or degree of exchange. Vapor-phase PSF provides a platform to modify the MOF porosity or even introduce new functionalities (e.g., luminescence photoswitching and catalytic activity). Third, since vapor-phase processing methods enable the integration of MOF film deposition into a (micro)fabrication workflow, they facilitate a range of applications with improved performance (low-k dielectrics, sensors, membrane separations, etc.). Finally, we provide a discussion on the limitations, challenges, and further opportunities for MOF-VPP. Through the discussion and analysis of the vapor-phase processing strategies as well as the underlying mechanisms in this Account, we hope to contribute to the development of the controllable synthesis, functionalization, and application of MOFs and related materials.

Postsynthetic Modification of Metal-Organic Frameworks by Vapor-Phase Grafting.

A vapor-phase grafting strategy is developed for the postsynthetic modification of metal-organic frameworks (MOFs). On the basis of the Schotten-Baumann reaction between acyl chloride (-COCl) and amino (-NH2) groups and hydrolysis of -COCl, the carboxylated MOFs could be prepared through simple exposure in vaporized acyl chloride molecules and immersion in water. The modified MOFs have well-maintained crystalline structures and porosities and show substantially improved fluoride removal performance.

Vapor-assisted self-conversion of basic carbonates in metal-organic frameworks.

Incorporation of nanoparticles has been considered as an efficient method for enhancing the adsorption performance of metal-organic frameworks (MOFs). Alkali metal compounds possess outstanding affinity to acidic CO2. In this study, a robust self-conversion strategy is reported for improving the carbon capture performance of MOFs, through directly transforming partial metal centers to basic carbonate (BC) nanoparticles. Based on the hydrolysis of coordination bonds induced by water impurity in solvents and the decarboxylation of linkers under thermal and alkaline conditions, the self-loading of BC in MOFs can be realized by solvent vapor-assisted thermal treatment. Since water impurity causes limited self-conversion and excess organic solvent can purify MOFs, the BC-MOF materials maintain good crystallinity and even show superior porosity. Owing to the increased specific surface areas, open metal sites, and alkalinity of BC, the prepared MOF composites exhibit substantially improved CO2 capture performance with good balance between capacity and selectivity. For example, after self-conversion with ethanol solvent, the CO2 adsorption capacity and CO2/N2 (15 : 85) selectivity at 298 K and 100 kPa increase from 3.7 mmol g-1 and 11.4 to 5.8 mmol g-1 and 29.2, respectively.

A Model for Predicting Malignant Sub-pleural Solid Masses Using Grayscale Ultrasound and Ultrasound Elastography.

This article aimed to establish a prediction model of grayscale sonography and ultrasound elastography for malignant sub-pleural solid masses and evaluate its diagnostic value. The study included 153 patients, including 89 patients with malignant tumors and 64 patients with benign diseases. Statistical differences between the malignant and benign groups were found in the factors of age, air bronchogram, borderline, shape and elasticity score (p < 0.05). Age, elasticity score and borderline were effective factors for predicting malignant sub-pleural solid masses, offering an area under the receiver operating characteristic curve (AUROC) value of 0.72 (95% confidence interval [CI] 0.64-0.80), 0.73 (95% CI 0.65-0.79) and 0.70 (95% CI 0.62-0.77), respectively. The AUROC value of the prediction model for malignant sub-pleural solid masses was 0.88 (95% CI 0.81-0.92), which indicates that the prediction model was able to improve the diagnostic accuracy and that it may prove a useful auxiliary diagnostic tool for malignant sub-pleural solid masses, especially in primary health care institutions in developing countries.

Metal Halide Perovskite Nanocrystals in Metal-Organic Framework Host: Not Merely Enhanced Stability.

As an emerging optical material, perovskite nanocrystals (NCs) exhibit excellent optoelectronic properties and show great potential for various optoelectronic applications. However, the inherent inferior stability against moisture, oxygen, light and heat limit their practical application. As well, the exploration and development of perovskite NCs with novel properties and functions are new challenges. To achieve these goals, the integration and encapsulation of perovskite NCs with multifunctional metal-organic frameworks (MOFs) to form perovskite NC@MOF composites, is a promising strategy for enhancing the stability and broadening the application scope. In this minireview, we summarize and discuss the synthesis strategies and functional mechanisms of perovskite NC@MOF composites, along with applications of light emitting diodes (LED), information security, photocatalysis, sensing, and detection. We further briefly point out the current challenges as well as the future opportunities for the emerged composite materials.

Photo-electrochemical detection of dopamine in human urine and calf serum based on MIL-101 (Cr)/carbon black.

A new photo-electrochemical sensor based on MIL-101(Cr) MOF/carbon black (CB) is fabricated and characterized. By using differential pulse voltammetry, dopamine (DA) can be effectively detected using a photo-electrochemical MIL-101(Cr)/CB sensor under visible light. The CB acts as the electron bridge to combine with the large specific surface area and photo-catalytic feature of MOF, which contribute to the improvements of sensitivity of DA detection. The concentration of the catalyst, pH value, accumulation potential, and accumulation time were also optimized. Furthermore, the electrochemical performances of MIL-101(Cr)/CB sensor was investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), scan rate, electrochemically active surface area (ECSA), and amperometric responses. A detection limit of 0.38 nM (LOD = 3 sb/S, sb = 0.028) and a working range of 1 nM to 2.22 µM has been achieved. The MIL-101(Cr)/CB sensor exhibits excellent reproducibility, stability, and selectivity and also has satisfactory recovery rate for the analysis of real samples including calf serum and human urine. Graphical abstract.

Influence of Alkyl Substitution Position on Wide-Bandgap Polymers in High-Efficiency Nonfullerene Polymer Solar Cells.

Two wide-bandgap (WBG) conjugated polymers (PBPD-p and PBPD-m) based on phenyl-substituted benzodithiophene (BDT) with the different substitution position of the alkyl side chain and benzodithiophene-4,8-dione (BDD) units are designed and synthesized to investigate the influence of alkyl substitution position on the photovoltaic performance of polymers in polymer solar cells (PSCs). The thermogravimetric analysis, absorption spectroscopy, molecular energy level, X-ray diffraction, charge transport and photovoltaic performance of the polymers are systematically studied. Compared with PBPD-p, PBPD-m exhibits a slight blue-shift but a deeper highest occupied molecular orbital (HOMO) energy level, a tighter alkyl chain packing and a higher hole mobility. The PBPD-m-based PSCs blended with acceptor IT-4F shows a higher power conversion efficiency (PCE) of 11.95% with a high open-circuit voltage (Voc ) of 0.88 V, a short-circuit current density (Jsc ) of 19.76 mA cm-2 and a fill factor (FF) of 68.7% when compared with the PCE of 6.97% with a Voc of 0.81 V, a Jsc of 15.97 mA cm-2 and an FF of 53.9% for PBPD-p. These results suggest that it is a feasible and effective strategy to optimize photovoltaic properties of WBG polymers by changing the substitution position of alkyl side chain in PSCs.

Air-thermal processing of hierarchically porous metal-organic frameworks.

Metal-organic frameworks (MOFs) show great potential for various applications. The functions of MOFs are closely related to their porous structures and lattice integrities. However, the generally existing guest solvent/linker molecules and crystalline defects will alter internal microstructures and microenvironments of MOFs. Meanwhile, although MOFs have tailorable pore structures within the range of microspores, the achievement of meso/macropores in MOFs is of scientific interest. Herein, a versatile air-thermal processing (ATP) strategy is reported to remove the residual molecules and incompletely coordinated linkers in MOFs. Through processing MOFs in confined space, the thermalized and pressurized air can assist the filling solvents and partially/totally uncoordinated linkers to overcome the energy barrier of escape, and then maximize MOF porosity. The obtained MOF materials with hierarchical micro/mesoporous structures display substantially improved adsorption capacities and selectivities. For example, CuBTC-A shows 36%, 72%, 22%, and 86% enhancements in surface area, pore volume, CO2 uptake, and CO2/N2 selectivity, respectively. Moreover, by adjusting processing temperature, the ATP strategy is available for fabricating MOF materials with hierarchically micro/meso/macroporous superstructures under modulator/template-free conditions.

Vapor-phase linker exchange of metal-organic frameworks.

Metal-organic frameworks (MOFs) have been attracting intensive attention because of their commendable potential in many applications. Postsynthetic modification for redesigning chemical characteristics and pore structures can greatly improve performance and expand functionality of MOF materials. Here, we develop a versatile vapor-phase linker exchange (VPLE) methodology for MOF modification. Through solvent-free and environment-friendly VPLE processing, various linker analogs with functional groups but not for straightforward MOF crystallization are inserted into frameworks as daughter building blocks. Besides single exchange for preparing MOFs with dual linkers, VPLE can further be performed by multistage operations to obtain MOF materials with multiple linkers and functional groups. The halogen-incorporated ZIFs exhibit good porosity, tunable molecular affinity, and impressive CO2/N2 and CH4/N2 adsorption selectivities up to 31.1 and 10.8, respectively, which are two to six times higher than those of conventional adsorbents. Moreover, VPLE can substantially enhance the compatibility of MOFs and polymers.

Phosphorus hyperaccumulation in nano-MgO using a circular recovery process based on multiple phase transitions from periclase to brucite.

Phosphorus recovery from water is not only necessary for the protection of aquatic environments but also to meet the needs of sustainable development. We find that the adsorption capacity of nano-MgO is far from being fully utilized because of its simultaneous hydration into brucite. Annealing is a useful method of recovering its adsorption capacity without the need for desorption. Phosphate can be accumulated to a much higher level, even surpassing its theoretical equilibrium adsorption limit, so that high-quality fertilizer can be obtained (115.9 mg-P/g-MgO). Phosphate ions exist as HPO42- and PO43- in the sorbent during its phase transition from periclase to brucite, which is the main reason for its extremely high and reactivatable phosphorus recovery properties. This finding not only provides a new efficient phosphorous recovery strategy but will also lead to new understandings of traditional reactive nano-sorbents.

Development of a solid-phase microextraction method for fast analysis of cyclic volatile methylsiloxanes in water.

Cyclic volatile methylsiloxanes (cVMS) are widely used in consumer products and commonly detected in the environment. There are challenges in the analysis of cVMS because of their ubiquitous use which can introduce high background contamination. The current study introduces a sample preparation method based on headspace of solid-phase microextraction (SPME) for monitoring the cVMS in waters. Efforts were made to reduce the background contamination during sample preparation and instrument analysis. A laboratory prepared MIL-101 coating was prepared using polysulfone instead of polydimethylsiloxane as adhesive to avoid the contamination. The extraction performance of the MIL-101 fiber was optimized and evaluated. The optimized extraction time and temperature were 60 min and 40 °C, respectively. The method quantification limits of the MIL-101 fiber for octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5) and dodecylcyclohexasiloxane (D6) in water were 0.15 ng mL-1, 0.14 ng mL-1, and 0.27 ng mL-1, respectively. The extraction efficiency of the proposed MIL-101 fiber was comparable to the commercial polydimethylsiloxane/divinylbenzene fiber. The developed method was applied to analyze the cVMS in wastewater treatment plant and the concentrations in the barscreen and in the aeration tank ranged from 0.73 to 3.3 ng mL-1 and 7.74-85.1 ng mL-1, respectively. The MIL-101 fiber was also applied to study the photodegradation of the cVMS in water under simulated sunlight. Approximately 25%, 20%, and 45% of D4, D5, and D6, respectively, were degraded after 10 h exposure.

In situ photoreduction of structural Fe(III) in a metal-organic framework for peroxydisulfate activation and efficient removal of antibiotics in real wastewater.

Structural Fe(III) is widely found in various coordination complexes and inorganic compounds. In this work, a typical Fe-based metal organic framework (MOF) (viz. MIL-100(Fe)) was chosen as an example in the activation of peroxydisulfate (PDS) for the removal of antibiotic pollutants. Interestingly, an auto-acceleration effect was observed in the process of MIL-100(Fe) activating PDS aided by visible light irradiation. Compared to the processes with MIL-100(Fe)-activated PDS alone and the photo-activated PDS alone, the degradation efficiency of sulfamethoxazole (SMX) obtained in the visible light assisted PDS activation by MIL-100(Fe) process was enhanced by 2.1 and 5.6 times, respectively. Therein, the photogenerated electrons from MIL-100(Fe) carried out an in situ reduction of the surface structural Fe(III) to form Fe(II), which in turn significantly improved the PDS activation efficiency in the generation of ·OH and O2-· radicals for the removal of SMX. The degradation pathways of SMX were deduced based on the experimental results and theoretical calculations. Acute toxicity estimation indicated the formation of less toxic products after the treatment of SMX. Additionally, degradation of five antibiotics in the real wastewater were investigated to further confirm the advantages of such in situ photoreduced structural Fe(III) in MOFs to activate the PDS process.

Efficient natural organic matter removal from water using nano-MgO coupled with microfiltration membrane separation.

Excess natural organic matter (NOM) in water not only lead to unpleasant black color and dissolved oxygen depletion in wastewater and natural water body but also causes carcinogenic chlorinated organic byproduct during drinking water chlorine disinfection. We try to develop a novel cost-effective and green technology for water NOM removal. In our simulated NOM removal process using humic acid (HA) as typical organic matter, we find that mesoporous nano-MgO performs an abnormally high NOM removal capacity (1260 mg-HA/g-MgO, or 446 mgC/g-MgO) when coupled with microfiltration membrane separation, which can't be illustrated by traditional adsorption mechanism. Actually, Mg2+ from dissolved Mg(OH)2 contributes ∼ 92% NOM removal via coagulation while Mg(OH)2 is responsible for the residue ∼ 8% via adsorption. MgO serves as a two-in-one coagulant and adsorbent. The MgO treatment process is highly pH sensitive and weak acidic condition is favored for high NOM removal efficiency. MgO can be regenerated for more than 10 circulations by annealing Mg(OH)2/Mg-NOM composite at 500 °C, so that our MgO recycling process will be sustainable without the need of continuous chemical purchase. More importantly, no solid waste is generated in this novel process. This MgO-recycling NOM-removal process is simple, efficient, and sustainable for water NOM removal and will be significant in promoting novel sustainable technologies for NOM- or HA-related water remediation and treatment while minimizing the generation of solid waste.