One Porphyrin Per Chain Self-Assembled Helical Ion-Exchange Channels for Ultrahigh Osmotic Energy Conversion

Electron-Withdrawing Substituents Enhance the Type I PDT and NIR-II Fluorescence of BODIPY J Aggregates for Bioimaging and Cancer Therapy

Organic dyes with simultaneously boosted near-infrared-II (NIR-II) fluorescence, type I photodynamic therapy (PDT), and photothermal therapy (PTT) in the aggregate state are still elusive due to the unclear structure-function relationship. Herein, electron-withdrawing substituents are introduced at the 5-indolyl positions of BODIPY dyes to form tight J-aggregates for enhanced NIR-II fluorescence and type I PDT/PTT. The introduction of an electron-rich julolidine group at the meso position and an electron-withdrawing substituent (-F) at the indolyl moiety can enhance intermolecular charge transfer and the hydrogen bonding effect, contributing to the efficient generation of superoxide radicals in the aggregate state. The nanoparticles of BDP-F exhibit NIR-II fluorescence at 1000 nm, good superoxide radical generation ability, and a high photothermal conversion efficiency (50.9%), which enabled NIR-II fluorescence-guided vasculature/tumor imaging and additive PDT/PTT. This work provides a strategy for constructing phototheranostic agents with enhanced NIR-II fluorescence and type I PDT/PTT for broad biomedical applications.

Large-Scale, Vertically Aligned 2D Subnanochannel Arrays by a Smectic Liquid Crystal Network for High-Performance Osmotic Energy Conversion

The osmotic energy, an abundant renewable energy source, can be directly converted to electricity by nanofluidic devices with ion-selective membranes. 2D nanochannels constructed by nanosheets possess abundant lateral interfacial ion-exchange sites and exhibit great superiority in nanofluidic devices. However, the most accessible orientation of the 2D nanochannels is parallel to the membrane surface, undoubtedly resulting in the conductivity loss. Herein, first vertically aligned 2D subnanochannel arrays self-assembled by a smectic liquid crystal (LC) network that exhibit high-performance osmotic energy conversion are demonstrated. The 2D subnanochannel arrays are fabricated by in situ photopolymerization of monomers in the LC phase. The as-prepared membrane exhibits excellent water-resistance and mechanical strength. The 2D subnanochannels with excellent cation selectivity and conductivity show high-performance osmotic energy conversion. The power density reaches up to about 22.5 W m-2 with NaCl solution under a 50-fold concentration gradient, which is among with ultrahigh power density. This membrane design concept provides promising applications in osmotic energy conversion.

Anti-Entropy Aggregation of Minority Groups in Polymers: Design and Applications

Minority groups are non-repeating units with very low content that inevitably exist in polymers. Typically, these minority groups are easily surrounded by the majority of repeating units and randomly dispersed, maximizing the entropy of minority groups. In the concept, anti-entropy aggregation (AEA) of minority groups is described, and different pathways are outlined. They are polymer crystallization-driven AEA, supramolecular interaction-induced AEA, phase separation-confined AEA, and hierarchical interactions-driven AEA. Typical applications of AEA materials are also presented, including fluorescence probes, self-healing materials, ion transporting regulation, and osmotic energy conversion. The concept of AEA is expected to inspire the fabrication of novel functional systems.

All-natural 2D nanofluidics as highly-efficient osmotic energy generators

Two-dimensional nanofluidics based on naturally abundant clay are good candidates for harvesting osmotic energy between the sea and river from the perspective of commercialization and environmental sustainability. However, clay-based nanofluidics outputting long-term considerable osmotic power remains extremely challenging to achieve due to the lack of surface charge and mechanical strength. Here, a two-dimensional all-natural nanofluidic (2D-NNF) is developed as a robust and highly efficient osmotic energy generator based on an interlocking configuration of stacked montmorillonite nanosheets (from natural clay) and their intercalated cellulose nanofibers (from natural wood). The generated nano-confined interlamellar channels with abundant surface and space negative charges facilitate selective and fast hopping transport of cations in the 2D-NNF. This contributes to an osmotic power output of ~8.61 W m-2 by mixing artificial seawater and river water, higher than other reported state-of-the-art 2D nanofluidics. According to detailed life cycle assessments (LCA), the 2D-NNF demonstrates great advantages in resource consumption (1/14), greenhouse gas emissions (1/9), and production costs (1/13) compared with the mainstream 2D nanofluidics, promising good sustainability for large-scale and highly-efficient osmotic power generation.

Ultramicroporous Tröger's Base Framework Membranes for pH-Neutral Aqueous Organic Redox Flow Batteries

Processable polymers of intrinsic microporosity (PIMs) are emerging as promising candidates for next-generation ion exchange membranes (IEMs). However, especially with high ion exchange capacity (IEC), IEMs derived from PIMs suffer from severe swelling, thus, resulting in decreased selectivity. To solve this problem, we report ultramicroporous polymer framework membranes constructed with rigid Tröger's Base network chains, which are fabricated via an organic sol-gel process. These membranes demonstrate excellent antiswelling, with swelling ratios below 4.5% at a high IEC of 2.09 mmol g-1, outperforming currently reported PIM membranes. The rigid ultramicropore confinement and charged modification of pore channels endow membranes with both very high size-exclusion selectivity and competitive ion conductivity. The membranes thus enable the efficient and stable operation of pH-neutral aqueous organic redox flow batteries (AORFBs). This work presents the advantages of polymer framework materials as IEMs and calls for increasing attention to extending their varieties and utilization in other applications.

Bacterial nanocellulose membrane with opposite surface charges for large-scale and large-area osmotic energy harvesting and ion transport

How to optimize ion-exchange membrane materials has been the key for researchers recently working on the use of reverse electrodialysis to harvest osmotic energy. Based on the considerations of improving membrane performance and conversion to large-area industrial production, this work first proposes an easy-industrialized strategy to treat bacterial cellulose membranes by hot pressing and hot pressing with etherification modification, and then to obtain anion-selective and cation-selective membrane pairs (PBC-M and NBC-M) with opposite charges. The PBC-M obtained by multi-step treatment has excellent hydrophobicity, good surface charge density, and more favorable nanochannel size for the functioning of double layer. The maximum output power density of 44.1 mW m-2 was obtained in artificial river water and seawater simulated salinity gradient power generation. Applied to a larger test area, the power output of the system where a single membrane is located can reach 2.2 × 10-3 mW, which is ahead of similar experimental products. The two membranes prepared can also be used in combination, which provides a new idea for full cell design. It's important to open up a new route for optimizing nanofluidic channel design, regulating ion flux transport, and advancing the large-scale industrialization of biomass nanofluidic membrane RED system.

Bacterially synthesized superfine tellurium nanoneedles as an antibacterial and solar-thermal still for efficient purification of polluted water

Bacterial biosynthesis of nanomaterials has several advantages (e.g., reduced energy inputs, lower cost, negligible environmental pollution) compared with traditional approaches. Various nanomaterials have been produced by bacteria. However, reports on using the bacterial biosynthesis of nanomaterials for applications with solar-thermal agents are scarce due to their narrow optical absorption. Herein, for the first time, we proposed a bacterial biosynthesis of broad-absorbing tellurium nanoneedles and demonstrated their effectiveness for solar-thermal evaporation and antibacterial applications. By simple biosynthesis within bacteria (Shewanella oneidensis MR-1), tellurium nanoneedles achieved a superfine configuration with a length-to-diameter ratio of nearly 20 and broad-spectrum absorbance. After integrating tellurium nanoneedles into a porous polyvinyl-alcohol scaffold, a solar-thermal still named TSAS-3 realized a high evaporation rate of 2.25 kg m-2 h-1 and solar-thermal conversion efficiency of 81% upon 1-Sun illumination. Based on these unique properties, the scaffold displayed good performances in seawater desalination, multiple wastewater treatment, and antibacterial applications. This work provides a simple and feasible strategy for the use of microbial-synthesized nanomaterials in solar-driven water purification and antibacterial applications.

Nano-Confined Effect and Heterojunction Promoted Exciton Separation for Light-Boosted Osmotic Energy Conversion

The osmotic energy conversion properties of biomimetic light-stimulated nanochannels have aroused great interest. However, the power output performance is limited by the low light-induced current and energy conversion efficiency. Here, nanochannel arrays with simultaneous modification of ZnO and di-tetrabutylammonium cis-bis(isothiocyanato)bis(2,20-bipyridyl-4,40-dicarboxylato) ruthenium (II) (N719) onto anodic aluminum oxide (AAO) to combine the nano-confined effect and heterojunction is designed, which demonstrate rectified ion transport behavior due to the asymmetric composition, structure and charge. High cation selectivity and ion flux contribute to the high power density of ≈7.33 W m-2 by mixing artificial seawater and river water. Under light irradiation, heterojunction promoted the production and separation of exciton, enhanced cation selectivity, and improved the utilization efficiency of osmotic energy, providing a remarkable power density of ≈18.49 W m-2 with an increase of 252% and total energy conversion efficiency of 30.43%. The work opens new insights into the biomimetic nanochannels for high-performance energy conversion.

Mono-component bacterial cellulose heterogeneous membrane mediated by ionic liquids for osmotic energy harvesting

The massive reserves of osmotic energy existing in estuary will be highly desired as promising energy source that avails to solve the problem of energy shortage and environment deterioration. The ion transport membrane is core component optimized through composite membrane heterostructure to maximize the osmotic energy harvesting but suffer from gaps and resistance increase, which limit their practical applications. Here we demonstrate mono-component heterogeneous regenerated bacterial cellulose (RBC) membranes fabricated by subtle regenerated technique through Ionic Liquids (ILs). Such membranes obtain heterogeneous nature by the difference in fiber intertwining states due to the different treatment conditions on both sides. It achieves osmotic energy conversion with maximum power density of 0.70 W·m-2at 100-fold, which provides ingenious strategy for excellent performance and low-cost osmotic energy harvesting. By minimizing pores and maximizing the surface charges, energy barriers can be lowered, ion permeable and selective transport channels for energy harvesting device can be increased, as supported by the numerical simulation. This is the first time the construction strategy for mono-component heterogeneous membrane mediated by ILs for osmotic energy harvesting is proposed, which averts gaps between the layers of different materials effectively and provides theoretical guidance for subsequent in-depth research on mono-component ion-selective heterogeneous membrane.

Bioinspired light-driven chloride pump with helical porphyrin channels

Halorhodopsin, a light-driven chloride pump, utilizes photonic energy to drive chloride ions across biological membranes, regulating the ion balance and conveying biological information. In the light-driven chloride pump process, the chloride-binding chromophore (protonated Schiff base) is crucial, able to form the active center by absorbing light and triggering the transport cycle. Inspired by halorhodopsin, we demonstrate an artificial light-driven chloride pump using a helical porphyrin channel array with excellent photoactivity and specific chloride selectivity. The helical porphyrin channels are formed by a porphyrin-core star block copolymer, and the defects along the channels can be effectively repaired by doping a small number of porphyrins. The well-repaired porphyrin channel exhibits the light-driven Cl- migration against a 3-fold concentration gradient, showing the ion pumping behavior. The bio-inspired artificial light-driven chloride pump provides a prospect for designing bioinspired responsive ion channel systems and high-performance optogenetics.

Confined amphipathic ionic-liquid regulated anodic aluminum oxide membranes with adjustable ion selectivity for improved osmotic energy conversion

To attain carbon neutrality and carbon peaking, there is an urgent need to convert the vast amount of blue energy present between seawater and river water into usable electricity. Reverse electrodialysis based on ion-exchange membranes is a promising way to efficiently achieve osmotic energy conversion. Anodic aluminum oxide (AAO) membranes are frequently used for osmotic energy harvesting because of their uniform nanopore channels, high flux, and excellent stability. However, the existing surface modification methods are complex and inefficient. In this study, an amphiphilic ionic liquid was selected to modify a porous anodic alumina membrane via simple capillary insertion. Due to the abundance of pH-dependent amphiphilic OH groups on the surface of AAO pore channels, the ionic liquids not only provide abundant surface charge but can also intelligently adjust its surface charge to different environments. In addition, it fills the AAO nanochannels to provide a continuous ion transport network. The modified hybrid membrane achieves efficient and stable osmotic energy conversion performance. This simple and feasible strategy paves the way for further improvements in commercial membranes.

Meta-Aerogel Ion Motor for Nanofluid Osmotic Energy Harvesting

Osmotic power, also known as "blue energy", is a vast, sustainable, and clean energy source that can be directly converted into electricity by nanofluidic membranes. However, the key technological bottleneck for large-scale osmotic electricity is that macroscopic-scale bulky membrane cannot synergistically satisfy the demands of high power density and low resistance without sacrificing scalability and mechanical robustness. Here, inspired by the anatomy and working principle of electric eels, which harness osmotic energy through embedded neuron-mediated fibril nanochannels with nanoconfined transport dynamics. Fibrous nanofluidic meta-aerogel ion motors, 3D-assembled from nanofluidic cable fibers with actuatable stimulation/transport "ion highways" are engineered. The meta-aerogel exhibits the integrated coupling effect of boosted ion propulsion and surface-charge-dominated selective ion transport. Driven by osmosis, the meta-aerogel ion motor can produce an unprecedented output power density of up to 30.7 W m-2 under a 50-fold salinity gradient. Advancing ultra-selective ion transport in nanofluidic meta-aerogels may provide a promising roadmap for blue energy harvesting.

Ultra-mechanosensitive Chloride Ion Transport through Bioinspired High-Density Elastomeric Nanochannels

Mechanosensitive ion channels play crucial roles in physiological activities, where small mechanical stimuli induce the membrane tension, trigger the ion channels' deformation, and are further transformed into significant electrochemical signals. Artificial ion channels with stiff moduli have been developed to mimic mechanosensory behaviors, exhibiting an electrochemical response by the high-pressure-induced flow. However, fabricating flexible mechanosensitive channels capable of regulating specific ion transporting upon dramatic deformation has remained a challenge. Here, we demonstrate bioinspired high-density elastomeric channels self-assembled by polyisoprene-b-poly4-vinylpyridine, which exhibit ultra-mechanosensitive chloride ion transport resulting from nanochannel deformation. The PI-formed continuous elastic matrix can transmit external forces into internal tensions, while P4VP forms transmembrane chloride channels that undergo dramatic deformation and respond to mechanical stimuli. The integrated and flexible chloride channels present a dramatic and stable electrochemical signal toward a low pressure of 0.2 mbar. This research first demonstrates the artificial mechanosensory chloride channels, which could provide a promising avenue for designing flexible and responsive channel systems.

High-Energy Sn-Ni and Sn-Air Aqueous Batteries via Stannite-Ion Electrochemistry

Tin is promising for aqueous batteries (ABs) due to its multiple electrons' reactions, high corrosion resistance, large hydrogen overpotential, and excellent environmental compatibility. However, restricted to the high thermodynamic barrier and the poor electrochemical kinetics, efficient alkaline Sn plating/stripping at facile conditions has not yet been realized. Here, for the first time, we demonstrate a highly reversible stannite-ion electrochemistry and construct a novel paradigm of high-energy Sn-based ABs. Combined spectroscopic characterization, electrochemical evaluation, and theoretical computation reveal the thermodynamic merits with a low reaction energy barrier and feasible H₂O participation in Sn-ion reduction as well as the kinetic merits with fastened surface charge transfer and SnO₂^2- diffusion. The resultant alkaline Sn anode delivers a low potential of -1.07 V vs Hg/HgO, a specific capacity of 450 mA h g^-1, a Coulombic efficiency of near 100%, superb rate capability at 45.5 A g^-1, and excellent cycling durability without dendrite and dead Sn. As a proof of concept, we developed new high-energy Sn-based ABs, including 1.45 V Sn-Ni with 314 W h kg^-1 (58 kW kg^-1 and over 15,000 cycles) and 1.0 V Sn-air with 420 W h kg^-1 (lifespan over 1900 h), on the basis of masses from cathode and anode active materials. The findings prove the feasibility of the alkaline Sn metal anode, and the new suite of high-energy Sn-based ABs may be of immediate benefit toward safe, reliable, and affordable energy storage.

Nickel hexacyanoferrate nanoparticle-decorated 3D rGO composites-based electrochemical sensing platform for detection of di-2-ethylhexyl phthalate

A label-free and efficient electrochemical (EC) sensing platform for di-2-ethylhexyl phthalate (DEHP) was developed based on in situ probe nickel hexacyanoferrate nanoparticle (NiHCF NP)-decorated three-dimensional reduced graphene oxide (3D rGO) composites. NiHCF NPs in the composites as an in situ probe show a pair of well-defined peaks with good reversibility and stability. Coupling 3D rGO with NiHCF NPs not only improved the electron transfer capability of NiHCF NPs but also provided more sites for aptamer immobilization. The synthesized NiHCF NP-decorated 3D rGO composites were used to act as a substrate for the immobilization of anti-DEHP aptamer by the covalent bonding method. The designed EC sensing platform displays excellent sensing performance for DEHP with a low detection limit of 3.64 pg/L, and a linear working range of 0.01 - 1000 ng/L. The application of the sensing platform to actual environmental samples was studied and satisfactory results were obtained. Thus, the proposed EC sensing platform would provide a potential tool for efficient detection of pollutants in the environment.

Engineering Polymeric Nanofluidic Membranes for Efficient Ionic Transport: Biomimetic Design, Material Construction, and Advanced Functionalities

Design elements extracted from biological ion channels guide the engineering of artificial nanofluidic membranes for efficient ionic transport and spawn biomimetic devices with great potential in many cutting-edge areas. In this context, polymeric nanofluidic membranes can be especially attractive because of their inherent flexibility and benign processability, which facilitate massive fabrication and facile device integration for large-scale applications. Herein, the state-of-the-art achievements of polymeric nanofluidic membranes are systematically summarized. Theoretical fundamentals underlying both biological and synthetic ion channels are introduced. The advances of engineering polymeric nanofluidic membranes are then detailed from aspects of structural design, material construction, and chemical functionalization, emphasizing their broad chemical and reticular/topological variety as well as considerable property tunability. After that, this Review expands on examples of evolving these polymeric membranes into macroscopic devices and their potentials in addressing compelling issues in energy conversion and storage systems where efficient ion transport is highly desirable. Finally, a brief outlook on possible future developments in this field is provided.

Supramolecular Anchoring of Polyoxometalate Amphiphiles into Nafion Nanophases for Enhanced Proton Conduction

Advanced proton exchange membranes (PEMs) are highly desirable in emerging sustainable energy technology. However, the further improvement of commercial perfluorosulfonic acid PEMs represented by Nafion is hindered by the lack of precise modification strategy due to their chemical inertness and low compatibility. Here, we report the robust assembly of polyethylene glycol grafted polyoxometalate amphiphile (GSiW₁₁) into the ionic nanophases of Nafion, which largely enhances the comprehensive performance of Nafion. GSiW₁₁ can coassemble with Nafion through multiple supramolecular interactions and realize a stable immobilization. The incorporation of GSiW₁₁ can increase the whole proton content in the system and induce the hydrated ionic nanophase to form a wide channel for proton transport; meanwhile, GSiW₁₁ can reinforce the Nafion ionic nanophase by noncovalent cross-linking. Based on these synergistic effects, the hybrid PEMs show multiple enhancements in proton conductivity, tensile strength, and fuel cell power density, which are all superior to the pristine Nafion. This work demonstrates the intriguing advantage of molecular nanoclusters as supramolecular enhancers to develop high-performance electrolyte materials.

Well-Defined Nanostructures by Block Copolymers and Mass Transport Applications in Energy Conversion

With the speedy progress in the research of nanomaterials, self-assembly technology has captured the high-profile interest of researchers because of its simplicity and ease of spontaneous formation of a stable ordered aggregation system. The self-assembly of block copolymers can be precisely regulated at the nanoscale to overcome the physical limits of conventional processing techniques. This bottom-up assembly strategy is simple, easy to control, and associated with high density and high order, which is of great significance for mass transportation through membrane materials. In this review, to investigate the regulation of block copolymer self-assembly structures, we systematically explored the factors that affect the self-assembly nanostructure. After discussing the formation of nanostructures of diverse block copolymers, this review highlights block copolymer-based mass transport membranes, which play the role of “energy enhancers” in concentration cells, fuel cells, and rechargeable batteries. We firmly believe that the introduction of block copolymers can facilitate the novel energy conversion to an entirely new plateau, and the research can inform a new generation of block copolymers for more promotion and improvement in new energy applications.