Construction and application of bioinspired nanochannels based on two-dimensional materials

Sensing creatinine in urine via the iontronic response of enzymatic single solid-state nanochannels

In this study, we investigate the integration of the enzyme creatinine deiminase into solid-state nanopore walls through electrostatic assembly for the development of creatinine sensors. In these asymmetric single nanochannels, ionic transport is determined by the surface charge inside the channel, resulting in diode-like behavior that rectifies ionic current. The efficiency of such rectification depends on the surface charge density. In the presence of creatinine, the enzymatic reaction generates ammonium, leading to an increase in local pH near the channel, which can be detected through changes in transmembrane ionic transport response. Changes in rectification efficiency can be well correlated with the analyte concentration, allowing for a detection limit of 5 nM creatinine. Furthermore, this solid-state nanopore-based device is capable of sensing in diluted urine samples, showing a good linear correlation between the response and the logarithm of the creatinine concentration over a wide range of concentrations (50 nM-100 μM). These results demonstrate the potential of systems based on the integration of enzymes that induce pH changes and solid-state nanopores for the development of biomarker sensors capable of operating in complex real samples.

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.

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.

Bio-inspired Double Angstrom-Scale Confinement in Ti-deficient Ti0.87 O2 Nanosheet Membranes for Ultrahigh-performance Osmotic Power Generation

Osmotic power, a clean energy source, can be harvested from the salinity difference between seawater and river water. However, the output power densities are hampered by the trade-off between ion selectivity and ion permeability. Here we propose an effective strategy of double angstrom-scale confinement (DAC) to design ion-permselective channels with enhanced ion selectivity and permeability simultaneously. The fabricated DAC-Ti0.87 O2 membranes possess both Ti atomic vacancies and an interlayer free spacing of ≈2.2 Å, which not only generates a profitable confinement effect for Na+ ions to enable high ion selectivity but also induces a strong interaction with Na+ ions to benefit high ion permeability. Consequently, when applied to osmotic power generation, the DAC-Ti0.87 O2 membranes achieved an ultrahigh power density of 17.8 W m-2 by mixing 0.5/0.01 M NaCl solution and up to 114.2 W m-2 with a 500-fold salinity gradient, far exceeding all the reported macroscopic-scale membranes. This work highlights the potential of the construction of DAC ion-permselective channels for two-dimensional materials in high-performance nanofluidic energy systems.

Two-Dimensional Graphene-Based Potassium Channels Built at an Oil/Water Interface

Graphene-based laminar membranes exhibit remarkable ion sieving properties, but their monovalent ion selectivity is still low and much less than the natural ion channels. Inspired by the elementary structure/function relationships of biological ion channels embedded in biomembranes, a new strategy is proposed herein to mimic biological K+ channels by using the graphene laminar membrane (GLM) composed of two-dimensional (2D) angstrom(Å)-scale channels to support a simple model of semi-biomembrane, namely oil/water (O/W) interface. It is found that K+ is strongly preferred over Na+ and Li+ for transferring across the GLM-supported water/1,2-dichloroethane (W/DCE) interface within the same potential window (-0.1-0.6 V), although the monovalent ion selectivity of GLM under the aqueous solution is still low (K+/Na+~1.11 and K+/Li+~1.35). Moreover, the voltammetric responses corresponding to the ion transfer of NH4+ observed at the GLM-supported W/DCE interface also show that NH4+ can often pass through the biological K+ channels due to their comparable hydration-free energies and cation-π interactions. The underlying mechanism of as-observed K+ selective voltammetric responses is discussed and found to be consistent with the energy balance of cationic partial-dehydration (energetic costs) and cation-π interaction (energetic gains) as involved in biological K+ channels.

Mechanical Mechanism of Ion and Water Molecular Transport through Angstrom-Scale Graphene Derivatives Channels: From Atomic Model to Solid-Liquid Interaction

Ion and water transport at the Angstrom/Nano scale has always been one of the focuses of experimental and theoretical research. In particular, the surface properties of the angstrom channel and the solid-liquid interface interaction will play a decisive role in ion and water transport when the channel size is small to molecular or angstrom level. In this paper, the chemical structure and theoretical model of graphene oxide (GO) are reviewed. Moreover, the mechanical mechanism of water molecules and ions transport through the angstrom channel of GO are discussed, including the mechanism of intermolecular force at a solid/liquid/ion interface, the charge asymmetry effect and the dehydration effect. Angstrom channels, which are precisely constructed by two-dimensional (2D) materials such as GO, provide a new platform and idea for angstrom-scale transport. It provides an important reference for the understanding and cognition of fluid transport mechanism at angstrom-scale and its application in filtration, screening, seawater desalination, gas separation and so on.

Research Progress in Preparation, Properties and Applications of Biomimetic Organic-Inorganic Composites with "Brick-and-Mortar" Structure

Inspired by nature, materials scientists have been exploring and designing various biomimetic materials. Among them, composite materials with brick-and-mortar-like structure synthesized from organic and inorganic materials (BMOIs) have attracted increasing attention from scholars. These materials have the advantages of high strength, excellent flame retardancy, and good designability, which can meet the requirements of various fields for materials and have extremely high research value. Despite the increasing interest in and applications of this type of structural material, there is still a dearth of comprehensive reviews, leaving the scientific community with a limited understanding of its properties and applications. In this paper, we review the preparation, interface interaction, and research progress of BMOIs, and propose possible future development directions for this class of materials.

Low dimensional nanomaterials for treating acute kidney injury

Acute kidney injury (AKI) is one of the most common severe complications among hospitalized patients. In the absence of specific drugs to treat AKI, hemodialysis remains the primary clinical treatment for AKI patients. AKI treatment has received significant attention recently due to the excellent drug delivery capabilities of low-dimensional nanomaterials (LDNs) and their unique therapeutic effects. Diverse LDNs have been proposed to treat AKI, with promising results and the potential for future clinical application. This article aims to provide an overview of the pathogenesis of AKI and the recent advances in the treatment of AKI using different types of LDNs. In addition, it is intended to provide theoretical support for the design of LDNs and implications for AKI treatment.

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.

Direct Wet-Spun Single-Walled Carbon Nanotubes-Based p-n Segmented Filaments toward Wearable Thermoelectric Textiles

Three-dimensional thermoelectric (TE) textiles (TETs) fabricated with TE filaments (TEFs) possess merits over other types such as thickness-direction thermal energy harvesting and excellent conformability with dynamic body curves, revealing the prospect of generating electricity for on-body application. Nonetheless, there is still a lack of a costless but scalable method to automatically and seamlessly produce in-series interconnected p-n segmented TEFs with high TE properties via conventional fiber spinning processes. Here, we developed an alternate wet-spinning strategy to continuously manufacture single-walled carbon nanotube-based p-n segmented TEFs at large scale. The TEF with high electrical conductivity (400-800 S cm^-1) displays a low contact resistivity of 189.8 μΩ cm² between the segments and interelectrode, showing 2 orders of magnitude smaller than that reported in the literature. More importantly, the power factors of p-type and n-type segments are 26.25 and 17.14 μW m^-1 K^-2, respectively, which are 3 and 4 orders of magnitude higher than those of advanced studies. We finally embroidered it into spacer fabric to fabricate a wearable TET, demonstrating an output power density of 501 nW m^-2 at ΔT = 27.7 K. The methodology can inspire the development of fiber-based electronics such as wearable TEs and diodes and so forth.