Supergravity-Steered Generic Manufacturing of Nanosheets-Embedded Nanocomposite Hydrogel with Highly Oriented, Heterogeneous Architecture.

Designing nanocomposite hydrogels with oriented nanosheets has emerged as a promising toolkit to achieve preferential performances that go beyond their disordered counterparts. Although current fabrication strategies via electric/magnetic force fields have made remarkable achievements, they necessitate special properties of nanosheets and suffer from an inferior orientation degree of nanosheets. Herein, a facile and universal approach is discovered to elaborate MXene-based nanocomposite hydrogels with highly oriented, heterogeneous architecture by virtue of supergravity to replace conventional force fields. The key to such architecture is to leverage bidirectional, force-tunable attributes of supergravity containing coupled orthogonal shear and centrifugal force field for steering high-efficient movement, pre-orientation, and stacking of MXene nanosheets in the bottom. Such a synergetic effect allows for yielding heterogeneous nanocomposite hydrogels with a high-orientation MXene-rich layer (orientation degree, f = 0.83) and a polymer-rich layer. The authors demonstrate that MXene-based nanocomposite hydrogels leverage their high-orientation, heterogeneous architecture to deliver an extraordinary electromagnetic interference shielding effectiveness of 55.2 dB at 12.4 GHz yet using a super-low MXene of 0.3 wt%, surpassing most hydrogels-based electromagnetic shielding materials. This versatile supergravity-steered strategy can be further extended to arbitrary nanosheets including MoS2, GO, and C3N4, offering a paradigm in the development of oriented nanocomposites.

Double charge flips of polyamide membrane by ionic liquid-decoupled bulk and interfacial diffusion for on-demand nanofiltration.

Fine design of surface charge properties of polyamide membranes is crucial for selective ionic and molecular sieving. Traditional membranes face limitations due to their inherent negative charge and limited charge modification range. Herein, we report a facile ionic liquid-decoupled bulk/interfacial diffusion strategy to elaborate the double charge flips of polyamide membranes, enabling on-demand transformation from inherently negative to highly positive and near-neutral charges. The key to these flips lies in the meticulous utilization of ionic liquid that decouples intertwined bulk/interfacial diffusion, enhancing interfacial while inhibiting bulk diffusion. These charge-tunable polyamide membranes can be customized for impressive separation performance, for example, profound Cl-/SO42- selectivity above 470 in sulfate recovery, ultrahigh Li+/Mg2+ selectivity up to 68 in lithium extraction, and effective divalent ion removal in pharmaceutical purification, surpassing many reported polyamide nanofiltration membranes. This advancement adds a new dimension to in the design of advanced polymer membranes via interfacial polymerization.

On-Water Surface Synthesis of Vinylene-Linked Cationic Two-Dimensional Polymer Films as the Anion-Selective Electrode Coating.

Vinylene-linked two-dimensional polymers (V-2DPs) and their layer-stacked covalent organic frameworks (V-2D COFs) featuring high in-plane π-conjugation and robust frameworks have emerged as promising candidates for energy-related applications. However, current synthetic approaches are restricted to producing V-2D COF powders that lack processability, impeding their integration into devices, particularly within membrane technologies reliant upon thin films. Herein, we report the novel on-water surface synthesis of vinylene-linked cationic 2DPs films (V-C2DP-1 and V-C2DP-2) via Knoevenagel polycondensation, which serve as the anion-selective electrode coating for highly-reversible and durable zinc-based dual-ion batteries (ZDIBs). Model reactions and theoretical modeling revealed the enhanced reactivity and reversibility of Knoevenagel reaction on the water surface. On this basis, we demonstrated the on-water surface 2D polycondensation towards V-C2DPs films that show large lateral size, tunable thickness, and high chemical stability. Representatively, V-C2DP-1 presents as a fully-crystalline and face-on oriented film with in-plane lattice parameters of a=b=~43.3 Å. Profiting from its well-defined cationic sites, oriented 1D channels, and stable frameworks, V-C2DP-1 film possesses superior bis(trifluoromethanesulfonyl)imide anion (TFSI-)-transport selectivity (transference, t-=0.85) for graphite cathode in high-voltage ZDIBs, thus triggering additional TFSI--intercalation stage and promoting its specific capacity (from ~83 to 124 mAh g-1) and cycling life (>1000 cycles, 95% capacity retention).

Harmonic amide bond density as a game-changer for deciphering the crosslinking puzzle of polyamide.

It is particularly essential to analyze the complex crosslinked networks within polyamide membranes and their correlation with separation efficiency for the insightful tailoring of desalination membranes. However, using the degree of network crosslinking as a descriptor yields abnormal analytical outcomes and limited correlation with desalination performance due to imperfections in segmentation and calculation methods. Herein, we introduce a more rational parameter, denoted as harmonic amide bond density (HABD), to unravel the relationship between the crosslinked networks of polyamide membranes and their desalination performance. HABD quantifies the number of distinct amide bonds per unit mass of polyamide, based on a comprehensive segmentation of polyamide structure and consistent computational protocols derived from X-ray photoelectron spectroscopy data. Compared to its counterpart, HABD overcomes the limitations and offers a more accurate depiction of the crosslinked networks. Empirical data validate that HABD exhibits the expected correlation with the salt rejection and water permeance of reverse osmosis and nanofiltration polyamide membranes. Notably, HABD is applicable for analyzing complex crosslinked polyamide networks formed by highly functional monomers. By offering a powerful toolbox for systematic analysis of crosslinked polyamide networks, HABD facilitates the development of permselective membranes with enhanced performance in desalination applications.

Self-Flipping Solar Seesaw Evaporators Leverage Scaling to De-Scale.

Salt scaling poses a significant obstacle to the practical implementation of solar-driven evaporation for desalination. Attempts to mitigate scaling by enhancing mass transfer often lead to a compromise in evaporation efficiency due to associated heat loss. In the present work, a novel seesaw evaporator with a Janus structure to harness scaling for periodic self-descaling is reported. The seesaw evaporators are facilely fabricated by delignifying balsa wood and subsequently single-sided spray-coating it with soot and polydimethylsiloxane (PDMS). This unique Janus structure enables the evaporator to float on the brine while ensuring an ample supply of solution for evaporation. During evaporation, salt ions are transported directionally toward the cocked end of the evaporator to form scaling, triggering the seesaw evaporator to flip once a threshold is reached. The accumulated salts re-dissolve back into the solution. By adjusting the tilt angle, the evaporator can achieve an impressive evaporation rate of up to 2.65 kg m-2  h-1 when evaporating an 8 wt.% NaCl solution. Remarkably, these evaporators maintain a stable evaporation rate during prolonged 120 h operation and produce ≈3.93-6.35 L m⁻2 ·day⁻¹ of freshwater from simulated brines when assembled into an evaporation device.

Supported Ionic Liquid Membrane with Highly-permeable Polyamide Armor by In Situ Interfacial Polymerization for Durable CO2 Separation.

Supported ionic liquid membranes (SILMs), owing to their capacities in harnessing physicochemical properties of ionic liquid for exceptional CO2 solubility, have emerged as a promising platform for CO2 extraction. Despite great achievements, existing SILMs suffer from poor structural and performance stability under high-pressure or long-term operations, significantly limiting their applications. Herein, a one-step and in situ interfacial polymerization strategy is proposed to elaborate a thin, mechanically-robust, and highly-permeable polyamide armor on the SILMs to effectively protect ionic liquid within porous supports, allowing for intensifying the overall stability of SILMs without compromising CO2 separation performance. The armored SILMs have a profound increase of breakthrough pressure by 105% compared to conventional counterparts without armor, and display high and stable operating pressure exceeding that of most SILMs previously reported. It is further demonstrated that the armored SILMs exhibit ultrahigh ideal CO2 /N2 selectivity of about 200 and excellent CO2 permeation of 78 barrers upon over 150 h operation, as opposed to the full failure of CO2 separation performance within 36 h using conventional SILMs. The design concept of armor provides a flexible and additional dimension in developing high-performance and durable SILMs, pushing the practical application of ionic liquids in separation processes.

Poly(N,N-diethylacrylamide)-endowed spontaneous emulsification during the breath figure process and the formation of membranes with hierarchical pores.

The spontaneous emulsification for the formation of water-in-oil (W/O) or oil-in-water (O/W) emulsions needs the help of at least one kind of the third component (surfactant or cosolvent) to stabilize the oil-water interface. Herein, with the water/CS2-soluble polymer poly(N,N-diethylacrylamide) (PDEAM) as a surfactant, the spontaneous formation of water-in-PDEAM/CS2 emulsions is reported for the first time. The strong affinity between PDEAM and water or the increase of PDEAM concentration will accelerate the emulsification process with high dispersed phase content. It is demonstrated that the spontaneous emulsification of condensed water droplets into the PDEAM/CS2 solution occurs during the breath figure process, resulting in porous films with two levels of pore sizes (i.e., micron and submicron). The emulsification degree and the amounts of submicron-sized pores increase with PDEAM concentration and solidifying time of the solution. This work brings about incremental interest in spontaneous emulsification that may happen during the breath figure process. The combination of these two simultaneous processes provides us with an option to build hierarchically porous structures with condensed and emulsified water droplets as templates. Such porous membranes may have great potential in fields such as separation, cell culture, and biosensing.

Solid-state, liquid-free ion-conducting elastomers: rising-star platforms for flexible intelligent devices.

Soft ionic conductors have emerged as a powerful toolkit to engineer transparent flexible intelligent devices that go beyond their conventional counterparts. Particularly, due to their superior capacities of eliminating the evaporation, freezing and leakage issues of the liquid phase encountered with hydrogels, organohydrogels and ionogels, the emerging solid-state, liquid-free ion-conducting elastomers have been largely recognized as ideal candidates for intelligent flexible devices. However, despite their extensive development, a comprehensive and timely review in this emerging field is lacking, particularly from the perspective of design principles, advanced manufacturing, and distinctive applications. Herein, we present (1) the design principles and intriguing merits of solid-state, liquid-free ion-conducting elastomers; (2) the methods to manufacture solid-state, liquid-free ion-conducting elastomers with preferential architectures and functions using advanced technologies such as 3D printing; (3) how to leverage solid-state, liquid-free ion-conducting elastomers in exploiting advanced applications, especially in the fields of flexible wearable sensors, bioelectronics and energy harvesting; (4) what are the unsolved scientific and technical challenges and future opportunities in this multidisciplinary field. We envision that this review will provide a paradigm shift to trigger insightful thinking and innovation in the development of intelligent flexible devices and beyond.

Room-temperature endogenous lubricant-infused slippery surfaces by evaporation induced phase separation.

We present a novel approach to fabricate endogenous slippery lubricant-infused porous surfaces (eSLIPS) at room temperature using an evaporation-induced phase separation process. The ternary coating system, comprising ethylene-propylene copolymer, caprylyl methicone, and n-hexane, forms a porous structure in situ infiltrated with lubricant, resulting in surfaces with remarkable anti-fouling and anti-icing properties.

Design of Photothermal "Ion Pumps" for Achieving Energy-Efficient, Augmented, and Durable Lithium Extraction from Seawater.

Extracting lithium from seawater has emerged as a disruptive platform to resolve the issue of an ever-growing lithium shortage. However, achieving highly efficient and durable lithium extraction from seawater in an energy-efficient manner is challenging, as imposed by the low concentration of lithium ions (Li+) and high concentration of interfering ions in seawater. Here, we report a facile and universal strategy to develop photothermal "ion pumps" (PIPs) that allow achieving energy-efficient, augmented, and durable lithium extraction from seawater under sunlight. The key design of PIPs lies in the function fusion and spatial configuration manipulation of a hydrophilic Li+-trapping nanofibrous core and a hydrophobic photothermal shell for governing gravity-driven water flow and solar-driven water evaporation. Such a synergetic effect allows PIPs to achieve spontaneous, continuous, and augmented Li+ replenishment-diffusion-enrichment, as well as circumvent the impact of concentration polarization and scaling of interfering ions. We demonstrate that our PIPs exhibit dramatic enhancement in Li+ trapping rate and outstanding Li+ separation factor yet have ultralow energy consumption. Moreover, our PIPs deliver ultrastable Li+ trapping performance without scaling even under high-concentration interfering ions for 140 h operation, as opposed to the significant decrease of nearly 55.6% in conventional photothermal configuration. The design concept and material toolkit developed in this work can also find applications in extracting high-value-added resources from seawater and beyond.

Interfacial polymerization at unconventional interfaces: an emerging strategy to tailor thin-film composite membranes.

Interfacial polymerization is a well-known process to synthesize separation layers for thin film composite membranes at an immiscible organic liquid-aqueous liquid interface. The organic-aqueous interface determines the diffusion dynamics of monomers and the chemical environment for polymerization, exerting a critical influence on the formation of polymer thin films. This review summarizes recent advances in tailoring interfacial polymerization using interfaces beyond the conventional alkane-water interface to achieve high-performance separation films with designed structures. Diverse liquid-liquid interfaces are introduced for synthesizing separation films by adding co-solvents into the organic phase and/or the aqueous phase, respectively, or by replacing one of the liquid phases with other solvents. Innovative liquid-gel and liquid-gas interfaces are then summarized for the synthesis of polymer thin films for separation. Novel strategies to form reaction interfaces, such as spray-coating, are also presented and discussed. In addition, we discuss the details of how a physically or chemically patterned substrate affects interfacial polymerization. Finally, the potential of unconventional interfaces in interfacial polymerization is forecast with both challenges and opportunities.

Photothermal Janus fabrics enabling persistent directional sweat-wicking in personal wet-thermal management.

Directional sweat-wicking by Janus fabrics has gained substantial attention in promoting personal wet-thermal management for optimal human comfort. During intense physical exercise, excessive sweating can cause the flooding of fabrics and weaken their wicking capabilities once the inner capillary channels are saturated. To address this issue, we develop a photothermal Janus fabric through a facile polydopamine (PDA) deposition followed by single-sided spray-coating of hydrophobic polydimethylsiloxane (PDMS). Such innovative fabrics enable directional sweat-wicking through a Janus structure and persistent removal of excessive sweat by solar-powered evaporation. Under sunlight, our photothermal Janus fabrics exhibit an enhanced evaporation rate, approximately twice compared with that of conventional Janus fabrics (∼1.143 ± 0.027 kg m-2h-1), making them suitable for high sweating rates during vigorous exercise. Furthermore, these fabrics help to maintain the skin temperature within the normal range, preventing hypothermia caused by profuse sweating. In addition, our photothermal Janus fabrics exhibit excellent washing durability even after multiple washing cycles, ensuring prolonged performance and safety.

A comprehensive review on the behavior and evolution of oil droplets during oil/water separation by membranes.

Membrane separation technology has significant advantages for treating oil-in-water emulsions. Understanding the evolution of oil droplets could reveal the interfacial and colloidal interactions, facilitate the design of advanced membranes, and improve the separation performances. This review on the characteristic behavior and evolution of oil droplets focuses on the advanced analytical techniques, and the subsequent fouling as well as demulsification effects during membrane separation. A detailed introduction is provided on microscopic observations and numerical simulations of the dynamic evolution of oil droplets, featuring real-time in-situ visualization and accurate reconstruction, respectively. Characteristic behaviors of these oil droplets include attachment, pinning, wetting, spreading, blockage, intrusion, coalescence, and detachment, which have been quantified by specific proposed parameters and criteria. The fouling process can be evaluated using Hermia and resistance models. The related adhesion force and intrusion pressure as well as droplet-droplet/membrane interfacial interactions can be accurately quantified using various force analysis methods and advanced force measurement techniques. It is encouraging to note that oil coalescence has been achieved through various effects such as electrostatic interactions, mechanical actions, Laplace pressure/surface free energy gradients, and synergistic effects on functional membranes. When oil droplets become destabilized and coalesce into larger ones, the functional membranes can overcome the limitations of size-sieving effect to attain higher separation efficiency. This not only bypasses the trade-off between permeability and rejection, but also significantly reduces membrane fouling. Finally, the challenges and potential research directions in membrane separation are proposed. We hope this review will support the engineering of advanced materials for oil/water separation and research on interface science in general.

Polystyrenes with both hydrophilic and hydrophobic moieties: synthesis and self-assembly behaviors.

Fluorinated polymers are emerging as important alternatives for isoporous film fabrication by the breath figure technique, originating from the special characteristics endowed by fluorine elements such as low surface energy and good chemical stability. In this work, we design and synthesize polystyrenes (∼3600 Da) with perfluoroalkyl groups (-C3F7 or -C7F15) at both chain ends and hydrophilic oligo(ethylene glycol) units ((C2H4O)n, n = 1/2/3) in the chain middle by taking advantage of the bifunctional atom transfer radical polymerization (ATRP) initiators and post-substitution of the terminal bromine. We investigate the influence of the two disparate groups on the physical characteristics of the polymers and self-assembly behaviors during the dynamic breath figure process. It shows that the elongation of hydrophilic segments can greatly decrease the interfacial tension between the polymer solution and water (from 41.8 to 37.4 mN m-1), and the functionalization with perfluoroalkyl end groups diminishes the ability of the polymers to precipitate at the interface, as demonstrated by the cloud point results. Studies of the morphology of the porous films suggest that both low interfacial tension and strong capability of interfacial precipitation are beneficial to droplet stabilization and honeycomb pattern formation at low solution concentrations.

A novel gatifloxacin-loaded intraocular lens for prophylaxis of postoperative endophthalmitis.

Postoperative endophthalmitis (POE) has been the most threatening complication after cataract surgery, which perhaps can be solved by the antibiotic-loaded intraocular lens (IOL). However, most drug-loaded IOLs demonstrate insufficient drug quantity, short release time, increased implantation-related difficulties or other noticeable drawbacks. To prevent POE and to address these deficiencies, a drug-loaded copolymer IOL, prepared from poly (urethane acrylate) prepolymer, isobornyl methacrylate (IBOMA), N-vinyl-2-pyrrolidone (NVP), Irgacure 819, RUVA-93, and gatifloxacin (GAT), was rapidly fabricated via photocuring and by using a 3D-printed mold. This composite displayed an outstanding and controllable GAT release behavior in vitro, a high light transmittance, and a moderate refractive index. Also, it demonstrated improved strain stress and elongation compared with the reference commercial acrylic IOL material. In vivo tests demonstrated satisfying released drug concentration at the early treatment stage. In vitro and in vivo studies further confirmed the remarkable bacterial inhibition and prevention of POE by the proposed IOL, which also displayed good biocompatibility. These findings suggested that the GAT-loaded IOL could be a promising implant to prevent and cure POE, also the proposed methods could inspire more designs for various medical applications.

Solar-Driven Evaporators with Thin-Film-Composite Architecture Inspired by Plant Roots for Treating Concentrated Nano-/Submicrometer Emulsions.

Oil/water separation by porous materials has received growing interest over the past years since the ever-increasing oily wastewater discharges seriously threaten our living environment. Purification of nano-sized and concentrated emulsions remains a big challenge because of the sharp flux decline by blocking the pores and fouling the surfaces of those porous materials. Herein, we propose a solar-driven evaporator possessing thin-film-composite architecture to deal with these two bottlenecks. Inspired by plant roots, our evaporator composes of a large-pore sponge wrapped by a thin hydrogel film, which is constructed by the contra-diffusion and cross-linking of alginate and calcium ions at the sponge surface. The dense superoleophobic hydrogel layer serves as a selective barrier that prevents oil emulsions but allows water permeation, while the inner sponge with large pores facilitates water transport within the evaporator, ensuring sufficient water supply for evaporation. By splitting the single evaporator into an array, the evaporator performs a high evaporation rate of ∼3.10 kg·m-2·h-1 and oil removal efficiency above 99.9% for a variety of oil emulsions. Moreover, it displays a negligible decline in the evaporation rate when treating concentrated emulsions for 8 h.

Metal-Polyphenol Coordination at the Aqueous Contra-diffusion "Interface": A Green Way to High-Performance Iron(III)/Tannic Acid Thin-Film-Composite Nanofiltration Membranes.

Thin-film-composite (TFC) nanofiltration membranes have found wide uses in environment remediation and industrial separation. There is a growing trend to avoid the use of organic solvents and toxic chemicals during membrane fabrication. Therefore, the aqueous fabrication of TFC membranes receives considerable interest as a green and sustainable process. However, it remains challenging to construct a defect-free and ultrathin film in a homogeneous aqueous phase without the assistance of an interface. The contra-diffusion process provides a special "interface" to confine the film formation within a narrow space by regulating the competition between precursor diffusion and interfacial reactions. Herein, Fe3+/tannic acid (TA) TFC membranes were fabricated by a contra-diffusion process. The effects of fabrication parameters on the Fe3+/TA TFC membrane microstructure and performance were also investigated. The negatively charged membrane performs a competitive Na2SO4 rejection of 95.6% with a permeation flux of 44.3 L m-2 h-1 under 0.6 MPa as well as more than 99.5% rejection to several anionic dyes. The as-prepared membranes perform superior nanofiltration performance compared to other reported Fe3+/TA-based membranes, owing to the thin and defect-free selective layers by self-regulation. Moreover, the membranes exhibit stable rejection during a long-term nanofiltration test.

Rapid Immobilization of Silver Nanoparticles via Amino-quinone Coatings Enables Surface-Enhanced Raman Scattering Detection.

Immobilization of metal nanoparticles (NPs) on flexible substrates for surface-enhanced Raman scattering (SERS) has received great attention. Anchoring NPs on substrates generally involves the process of surface modification, thanks to its simple, universal, and nondestructive features. 2-Hydroxy-1,4-naphthoquinone (HNQ), a plant-derived compound used to dye hairs and nails, may interact with polyamine or metal ions to form a surface coating. Here, we report the formation of amino-quinone coatings via the co-deposition of HNQ and polyethyleneimine, which provides a functionalized platform to rapidly immobilize Ag NPs on substrates such as a poly(dimethylsiloxane) (PDMS) film to fabricate Ag-PDMS substrates for SERS detection. The detection concentrations are down to 10-8 M for rhodamine 6G. This work expands the system of surface co-deposition and further provides a facile route to prepare a highly efficient SERS substrate.

Ultrafast Interfacial Self-Assembly toward Supramolecular Metal-Organic Films for Water Desalination.

Supramolecular metal-organic materials are considered as the ideal candidates for membrane fabrication due to their excellent film forming characteristics, diverse metal centers and ligand sources, and designable structure and function. However, it remains challenging to rapidly construct highly permeable supramolecular metal-organic membranes with high salt rejection. Herein, a novel ultrafast interfacial self-assembly strategy to prepare supramolecular metal-organic films through the strong coordination interaction between highly active 1,3,5-triformylphloroglucinol (TFP) ligands and Fe3+ , Sc3+ , or Cu2+ at the organic-aqueous interface is reported. Benefiting from the self-completing and self-limiting characteristics of this interfacial self-assembly, the new kind of supramolecular membrane with optimized composition can be assembled within 3.5 min and exhibits ultrathin, dense, defect-free features, and thus shows an excellent water permeance (21.5 L m-2  h-1  bar-1 ) with a high Na2 SO4 rejection above 95%, which outperforms almost all of the non-polyamide membranes and commercially available nanofiltration membranes. This strong-coordination interfacial self-assembly method will open up a new way for the development of functional metal-organic supramolecular films for high-performance membrane separation and beyond.

Porous Photo-Fenton Catalysts Rapidly Triggered by Levodopa-Based Mussel-Inspired Coatings for Enhanced Dye Degradation and Sterilization.

The advanced oxidation process of the photo-Fenton reaction can produce hydroxyl radicals with extremely strong oxidizing properties for the efficient and green degradation of various chemical and microbial pollutants. Herein, we report an approach to fabricating heterogeneous Fenton catalysts of ß-FeOOH nanorods on porous substrates triggered by mussel-inspired coatings of levodopa (3,4-dihydroxy-phenyl-l-alanine, l-DOPA) and polyethylenimine (PEI) for efficient photocatalytic dyes' degradation and sterilization. The l-DOPA-based coatings not only promote the formation and immobilization of ß-FeOOH nanorods on the porous substrates by strong coordination between catechol/carboxyl groups and Fe3+ but also improve the energy band structure of the Fenton catalysts through a valence band blue shift and band gap narrowing. The photo-Fenton catalysts prepared by the l-DOPA-based coatings exhibit high electron transport efficiency and improved utilization of sunlight. Only 2 h of mineralization is needed to fabricate these catalysts with excellent photocatalytic efficiency, in which the degradation efficiency of methylene blue can reach 99% within 30 min, whereas the sterilization efficiency of E. coli/S. aureus can reach 93%/94% within 20 min of the photo-Fenton reaction. Additionally, the prepared catalysts reveal a high photodegradation performance for various dyes including methylene blue, methyl blue, methyl orange, direct yellow, and rhodamine B. Furthermore, the catalysts retain high dye degradation efficiencies of above 90% after five photodegradation cycles, indicating cycling performance and good stability.