Aligned Nanochannels Research Articles

Advanced ion-selective wood membranes: Leveraging aligned cellulose nanofibers for enhanced osmotic energy conversion

Nanofluidic reverse electrodialysis (RED) is widely recognized as an exceptionally effective method for harvesting osmotic energy. Nevertheless, its progress has been impeded by the high costs and intricate fabrication processes associated with the required ion exchange membranes. The ion-selective wood membranes (ISWM) are derived directly from natural wood through a meticulously designed two-step chemical modification and densification process. The obtained ISWM with a highly charged surface effectively preserves the alignment of nanochannels from the cellulose fibers sourced in natural wood. Moreover, the laminated structure consisting of oriented nanofibers enhances ion conductivity by a factor of 4 compared to natural wood birch under low KCl concentrations. The charged and aligned nanochannels serve as nanofluidic conduits, facilitating selective ion transport. This, in turn, engenders efficient charge separation and the generation of an electrochemical potential difference. In energy harvesting systems such as ISWM-RED, the synergistic interplay between the electrochemical potential difference and ionic flux manifests in a remarkable output power density, reaching up to 658 mW m−2 to a salinity gradient of KCl at a magnitude of 50-fold. ISWM is an outstanding nanofluidic material that provides a cost-effective and easy-to-prepare solution for producing natural nanofluidic materials. Our investigation delineates a promising trajectory for developing high-performance nanofluidic RED devices tailored for efficient osmotic energy harvesting from renewable and abundant natural resources.

High-aligned oppositely-charged nanocellulose/MXene aerogel membranes through synergy of directional freeze-casting and structural densification for osmotic-energy harvesting

Optimization of ion-transport paths can considerably improve ion-transport capabilities in charged nanochannels. Thus, the assembly of high-charge-density one- and two-dimensional nanomaterials into aligned nanochannels is necessary for high-performance osmotic-energy harvesting. Herein, we prepared cellulose/MXene aerogel membranes with opposite charges and aligned nanochannels via chemical modification on algal cellulose nanofibers and MXene nanosheets, unidirectional freeze casting, and structural densification to considerably enhance the ionic conductivity in low-concentration solutions (maximum conductivity of 2.88 × 10−3 S cm−1). In particular, the aligned membrane had an output power density of 2.97 and 4.89 times higher than membranes used for suction filtration and isotropic nanochannels, respectively, demonstrating the necessity for nanostructure control. In addition, due to the photothermal effect of MXene, the positively–negatively (P–N) charged unit produced a maximum output power density of 8.87 W m−2 under a concentration gradient of artificial seawater and river water and simulated sunlight. Moreover, the unit maintained 90.4% of its original output capacity after 168 h of operation. As a proof of concept, we created nine series of P–N units and successfully powered an electronic calculator with an output voltage of 1.85 V. This study reveals improvements in developing renewable materials with an aligned nanostructure for high-performance osmotic-energy conversion.

Building artificial aligned nanochannels for highly efficient ion transport

Building artificial aligned nanochannels for highly efficient ion transport

A 2D Ultrathin Nanopatterned Interlayer to Suppress Lithium Dendrite Growth in High-Energy Lithium-Metal Anodes.

A novel strategy for robust and ultrathin (<1 µm) multilayered protective structures to address uncontrolled Lithium (Li) dendrite growth at Li-metal battery anodes is reported. Synergetic interaction among Ag nanoparticles (Ag NPs), reduced graphene oxide (rGO) films, and self-assembled block-copolymer (BCP) layers enables effective suppression of dendritic Li growth. While Ag NP layer confines the growth of Li metal underneath the rGO layer, BCP layer facilitates the fast and uniformly distributed flux of Li-ion transport and mechanically supports the rGO layer. Notably, highly aligned nanochannels with ≈15nm diameter and ≈600nm length scale interpenetrating within the BCP layer offer reversible well-defined pathways for Li-ion transport. Dramatic stress relaxation with the multilayered structure is confirmed via structural simulation considering the mechanical stress induced by filamentary-growth of Li metal. Li-metal anodes modified with the protective layer well-maintain stable reaction interfaces with limited solid-electrolyte interphase formation, yielding outstanding cycling stability and enhanced rate capability, as demonstrated by the full-cells paired with high-loading of LiFePO4 cathodes. The idealized design of multilayer protective layer provides significant insight for advanced Li-metal anodes.

Salinity‐Gradient Power Generation with Ionized Wood Membranes

AbstractReverse electrodialysis (RED) is known as an efficient way of converting the salinity gradient between river water and sea water into energy. However, the high cost and complex fabrication of the necessary ion exchange membranes greatly prohibit the development of the RED process. For the first time, an ionized wood membrane is demonstrated for this application, benefiting from the advantages of natural wood, which is abundant, low cost, sustainable, and easy to scale. The wood membrane maintains the aligned nanochannels of the cellulose nanofibers derived from the natural wood. The surface of the nanochannels can be functionalized to positively or negatively charged by in situ modifying the hydroxyl groups on the cellulose chains to quaternary ammonium or carboxyl groups, respectively. These charged aligned nanochannels serve as nanofluidic passages for selective ion transport with opposite polarity through the wood membrane, resulting in efficient charge separation and generating an electrochemical potential difference. The all‐wood RED device with 100 cells using a scalable stacking geometry generates an output voltage as high as 9.8 V at open circuit from a system of synthetic river water and sea water.

3D phosphorus-carbon electrode with aligned nanochannels promise high-areal-capacity and cyclability in lithium-ion battery

Abstract Despite of poor electrical conductivity and large volume expansion, low mass loading of phosphorus-based electrode severely decrease overall gravimetric/volumetric energy density, impeding its practical application in lithium ion batteries (LIBs). Herein, we construct a high-areal-capacity P@rGO-ACW electrode by warping phosphorus with rGO and confining in 3D microchanneled carbon matrix (P@rGO-ACW). The conductive 3D carbon scaffold (ACW) derived from natural wood acts as integrated porous current collector to accelerate the electrons/ions transport, while the vertical-alignment microchannels confine phosphorus and accommodate its volume expansion. The unique feature of phosphorus‑carbon electrode with 3D aligned nanochannels allows for a considerable improvement in high-areal-capacity and cyclability even in case of high mass loading. As expected, the P@rGO-ACW electrode can deliver a superior lithium storage capacity of 12.5 Ah cm−2 at a current of 0.5 mA cm−2 and a stable cycling performance of 9.5 Ah cm−2 at 1.0 mA cm−2 with a phosphorus mass loading of 16.6 mg cm−2. Our approach provides a versatile methodology to explore high mass-loading electrode towards developing high energy LIBs.

Electrospun functional micro/nanochannels embedded in porous carbon electrodes for microfluidic biosensing

We present a straightforward method for fabricating functional micro-, submicro-, and nano-channels embedded in a porous carbon film and the application of this microfluidic platform for electrochemical sensing. A skin layer of poly(methyl methacrylate) (PMMA) fibers was first electrospun on a thoroughly cleaned Si wafer substrate, followed by spin coating of a polyacrylonitrile (PAN) film on top of the skin. High-temperature carbonization of the composite film decomposed the PMMA fibers and produced embedded microchannels in the PAN-derived amorphous monolithic carbon electrode. The channels were decorated with Pt nanoparticles by in situ thermal decomposition of a precursor metal salt to enhance functionality of the carbon electrode. Carbon electrodes decorated with Pt nanoparticles (carbon-Pt), with and without embedded microchannels, were used to detect the food toxin aflatoxin B1 (AFB1) by surface biofunctionalization with the antibodies of AFB1 (anti-AFB1) via an electrochemical impedance technique. The aligned nanochannels in the porous carbon film act as a reaction chamber for antigen–antibody interactions and provide channels for fast electron transport toward the electrode from the electrolyte, resulting in improved electrochemical performance of the biosensor. The fabricated immunosensor is highly sensitive to 1pg/mL of AFB1 with a concentration range of 10−12–10−7g/mL.

Directed Assembly of Block Copolymer Templates for the Fabrication of Mesoporous Silica Films with Controlled Architectures via 3-D Replication

Mesoporous silica films with cylindrical or spherical pores up to 40 nm in diameter were fabricated by replicating the morphologies of polystyrene-b-poly(tert-butyl acrylate), PS-b-PtBA, copolymers using CO2-assisted infusion and phase selective condensation of tetraethylorthosilicate within the polymer template. The template structures, including domain packing, orientation and spacing were controlled by adjusting the molecular weight, volume fraction and polydispersities of the block copolymers and by solvent annealing. Cylinder alignment was achieved in polymer templates through directed self-assembly (DSA). The structural details imparted to the template prior to precursor infusion were retained in the mesoporous films. In one example, aligned PS-b-PtBA templates were replicated to yield massively parallel arrays of cylindrical pores with pore diameters up to ∼20 nm. The ability to tune pore sizes in this range within aligned nanochannels is attractive for applications involving biomolecules.

Phase transitions and molecular dynamics ofn-hexadecanol confined in silicon nanochannels

We present a combined x-ray diffraction and infrared spectroscopy study on the phase behavior and molecular dynamics of $n$-hexadecanol in its bulk state and confined in an array of aligned nanochannels of 8 nm diameter in mesoporous silicon. Under confinement, the transition temperatures between the liquid, the rotator ${R}_{\text{II}}$, and the crystalline C phase are lowered by approximately 20 K. While bulk $n$-hexadecanol exhibits at low temperatures a polycrystalline mixture of orthorhombic $\ensuremath{\beta}$ and monoclinic $\ensuremath{\gamma}$ forms, geometrical confinement favors the more simple $\ensuremath{\beta}$ form: only crystallites are formed, where the chain axis is parallel to the layer normal. However, the $\ensuremath{\gamma}$ form, in which the chain axis is tilted with respect to the layer normal, is entirely suppressed. The $\ensuremath{\beta}$ crystallites form bilayers that are not randomly orientated in the pores. The molecules are arranged with their long axis perpendicular to the long channel axis. With regard to the molecular dynamics, we were able to show that confinement does not affect the innermolecular dynamics of the ${\text{CH}}_{2}$ scissor vibration and to evaluate the intermolecular force constants in the C phase.

Proton NMR and Magnetic Susceptibility in a-Si:H

ABSTRACTProton nuclear magnetic resonance (NMR) is an important tool for characterizing the structure of a-Si:H over a wide range of length scales including short- and medium-range order as well as nanostructures. Some of the structural information obtained by NMR is based directly on proton NMR characteristics such as the lineshape and dipolar interactions that probe distances between hydrogen atoms and hydrogen environment. Based on such information it is shown that hydrogenated multi-vacancy model for Si-H clusters is fully consistent with both experimental and theoretical observations. It is demonstrated thatchanges of short- and medium-range order can be detected by measuring the magnetic susceptibility χ. Here ï is not directly related to NMR characteristics and NMR is used merely as a sensitive and accurate magnetometer. The result indicates that a-Si:H prepared by hot-wire CVD (HWCVD) and plasma-enhanced CVD (PECVD) with high H-dilution have higher structural order compared to conventional a-Si:H. By carrying out NMR measurements on single a-Si:H thin film new NMR features were observed such as the orientation dependence of the proton NMR spectrum with respect to the magnetic field. Based on such orientation dependence, strong evidence of aligned nano-channels was obtained in some device quality a-Si:H films.

Lateral growth of silicalite-1 crystal membrane on glass slabs

By the control of hydrothermal synthesis, lateral-oriented silicalite-1 membrane was synthesized on a glass slab, which posseses uniform aligned nano-channels in a large scale and results in a new host material for the study host-guest science.