Interconnected Nanopores Research Articles

Nanoscale Understanding on CO2 Diffusion and Adsorption in Clay Matrix Nanopores: Implications for Carbon Geosequestration.

Carbon capture and storage (CCS) in subsurface reservoirs represents a highly promising and viable strategy for mitigating global carbon emissions. In the context of CCS implementation, it is particularly crucial to understand the complex molecular diffusive and adsorptive behaviors of anthropogenic carbon dioxide (CO2) in the subsurface at the nanoscale. Yet, conventional molecular models typically represent only single-slit pores and overlook the complexity of interconnected nanopores. In this work, finite kaolinite lamellar assemblages with abundant nanopores (r < 2 nm) were used. Molecular dynamics simulations were performed to quantify the spatial distribution correlations, adsorption preference, diffusivity, and residence time of the CO2 molecules in kaolinite nanopores. The movement of the CO2 molecules primarily occurs in the central and proximity regions of the siloxane surfaces, progressing from larger to smaller nanopores. CO2 prefers smaller nanopores over larger ones. The diffusion coefficients increase, while residence times decrease, with the pore size increasing, differing from typical slit-pore models due to the pore shape and interconnectivity. The perspectives in this study, which would be challenging in conventional slit-pore models, will facilitate our comprehension of the CO2 molecular behaviors in the complex subsurface clay sediments for developing quantitative estimation techniques throughout the CCS project durations.

Direct synthesis of lightweight fiber sponges with interconnected nanopores structured fibers for absorbing low-frequency noise

Noise pollution from transportation industries poses many challenges to people’s health and the global economy. Most noise-absorbing materials suffer from the difficulty of achieving good noise absorption while maintaining light weight. In this study, we propose a feasible strategy to assemble porous fiber sponges (PPFS) based on electrospinning method. Modulating the phase separation rate of charged jet allows for the direct assembly of fiber sponges consisting of interconnected nanopores (30–70 nm) structured fibers. The resultant PPFS possess lightweight feature (volume density of 9.06 mg cm−3) and good mechanical properties (full recovery from 60% deformation). The sponges also show excellent low-frequency sound-absorbing performance (the sound absorption coefficient at 500 Hz is 0.78). Meanwhile, the noise reduction coefficient (NRC) of the fiber sponges reaches 0.57 when thickness is 30 mm, which could absorb white noise and high decibel noise efficiently. This work offers a fresh solution to develop lightweight and efficient sound-absorbing materials.

Ultrathin Aerogel Micro/Nanofiber Membranes with Hierarchical Cellular Architecture for High-Performance Warmth Retention.

A low temperature environment poses significant challenges to the global economy and public health. However, the existing cold-protective materials still struggle with the trade-off between thickness and thermal resistance, resulting in poor thermal-wet comfort and limited personal cold protection performance. Here, a scalable strategy, based on electrospinning and solution casting, is developed to create aerogel micro/nanofiber membranes with a hierarchical cellular architecture by manipulating the phase separation of the charged jets and of the spreading casting solution. The integration of interconnected nanopores (30-60 nm), ultrafine fiber diameter, and high porosity, enables the aerogel micro/nanofiber membranes with lightweight, ultrathin thickness (∼0.5 mm), and superior warmth retention performance with ultralow thermal conductivity of 14.01 mW m-1 K-1. And the resultant membrane with customized semiclosed walls exhibits both striking wind resistance and satisfactory thermal-wet comfort (3.4 °C warmer than the cutting-edge thermal underwear). This work will inspire the design and development of high-performance fibrous materials for thermal management applications.

Polysulfide regulation by defect-modulated Ta3N5−x electrocatalyst toward superior room-temperature sodium-sulfur batteries

Resolving low sulfur reaction activity and severe polysulfide dissolution remains challenging in metal-sulfur batteries. Motivated by a theoretical prediction, herein, we strategically propose nitrogen-vacancy tantalum nitride (Ta3N5−x) impregnated inside the interconnected nanopores of nitrogen-decorated carbon matrix as a new electrocatalyst for regulating sulfur redox reactions in room-temperature sodium-sulfur batteries. Through a pore-constriction mechanism, the nitrogen vacancies are controllably constructed during the nucleation of Ta3N5−x. The defect manipulation on the local environment enables well-regulated Ta 5d-orbital energy level, not only modulating band structure toward enhanced intrinsic conductivity of Ta-based materials, but also promoting polysulfide stabilization and achieving bifunctional catalytic capability toward completely reversible polysulfide conversion. Moreover, the interconnected continuous Ta3N5−x-in-pore structure facilitates electron and sodium-ion transport and accommodates volume expansion of sulfur species while suppressing their shuttle behavior. Due to these attributes, the as-developed Ta3N5−x-based electrode achieves superior rate capability of 730 mAh g−1 at 3.35 A g−1, long-term cycling stability over 2000 cycles, and high areal capacity over 6 mAh cm−2 under high sulfur loading of 6.2 mg cm−2. This work not only presents a new sulfur electrocatalyst candidate for metal-sulfur batteries, but also sheds light on the controllable material design of defect structure in hopes of inspiring new ideas and directions for future research.

Nanoporous thin films of hydrophobic block copolymers enabled by selective swelling for membrane distillation

Membrane distillation (MD) is receiving growing interest because of its >99.9% salt rejection even with low-grade waste heat as the energy supply. However, MD membranes are prone to be wetted and usually require complicated modification strategies to gain sufficient hydrophobicity. In this work, we report a new type of MD membranes with hydrophobic films carrying pores in the ultrafiltration range as the separation layers. Such membranes are prepared by coating an A-B-A triblock copolymer polystyrene-block-polydimethylsiloxane-block-polystyrene (PS-b-PDMS-b-PS, further abbreviated as SDS) on the macroporous PVDF substrate, followed by soaking in alkanes to cavitate the SDS coating layers following the mechanism of selective swelling. The PDMS microdomains in the SDS layers are converted to interconnected nanopores, and the PDMS blocks are enriched along the pore walls and membrane surface, endowing the membranes with intrinsic hydrophobicity. Thus-prepared SDS membranes exhibit stable rejection to NaCl (>99.99%) and high permeate flux up to 32.8 kg m−2 h−1, better than most MD membranes with large pores in the microfiltration range. Moreover, the SDS membranes display excellent wetting resistance, good heat resistance, and long-term stability. This work provides a new strategy to prepare MD membranes enabled by selective swelling of hydrophobic block copolymers, and demonstrates the great potential of hydrophobic ultrafiltration membranes in the long-term use in membrane distillation.

Refractive Index-Adaptive Nanoporous Chiral Photonic Crystal Film for Chemical Detection Visualized via Selective Reflection.

Photonic crystals (PC) are of great importance in technology, especially in optics and photonics. In general, the structural color of PCs responds to external stimuli primarily by changing their periodicity. Herein, the authors report on refractive index (RI) adaptive PCs. Cross-linked cholesteric films with interconnected nanopores exhibit a very low RI without light scattering. Transparent PC films with maximum reflectance in the ultravoilet(UV)region respond to various chemicals by changing the reflective color of the PC. The authors demonstrate its unique colorimetric chemical detections of hazardous organic liquids. Loading various chemicals into nanopores significantly shifts the structural color into the visible range depending on the chemical's RI. These results are unique in that the structural color of photonic films is mediated by RI changes rather than periodicity changes. In principle, nanoporous photonic crystal films can detect the RI of a chemical substance by its unique color. In contrast to volumetric changes, this sensing mechanism offers several advantages, including durability, excellent sensitivity, fast response time, and wide detection range. These results provide useful insight into stimulus-responsive PCs. The structural color of PC films can be effectively tuned by adjusting average RIs instead of changing periodicity.

Memristive and Tunneling Effects in 3D Interconnected Silver Nanowires.

A network of silver nanowires (Ag-NWs) is grown by electrodeposition in a nanoporous membrane with interconnected nanopores. This bottom-up approach fabrication method gives a conducting network with a 3D architecture and a high density of Ag-NWs. The network is then functionalized during the etching process, which leads to a high initial resistance as well as memristive behavior. The latter is expected to arise from the creation and the destruction of conducting silver filaments in the functionalized Ag-NW network. Moreover, after several cycles of measurement, the resistance of the network switches from a high-resistance regime in the GΩ range with tunnel conduction to a low-resistance regime presenting negative differential resistance in the kΩ range.

The impact of secondary channels on the wetting properties of interconnected hydrophobic nanopores

Pores in nanoporous materials can be interconnected in different ways; preliminary evidence exists that connecting channels can affect the overall hydrophobicity of the material thus providing an additional parameter in designing applications that require controlled wetting properties. In this work, we show that the length of secondary channels is a key parameter to tune the overall hydrophobicity of the material: short secondary channels make the main pore effectively more hydrophilic than a simple cylindrical pore, while long secondary channels enhance its hydrophobicity, producing the macroscopic effect of superhydrophobic textures. This rich behavior is rooted in the spontaneous filling of the secondary channels, which is unexpected based on classical capillarity. This length-dependent filling is explained by the formation of hydrogen bonds bridging the main pores which becomes less frequent with longer channels. These findings could be useful for designing nanoporous materials with tailored wetting properties.

Synthesis of nanoporous copper by dealloying CuZrAl and CuZrAlAg amorphous ribbons in acidic solution

In this paper, the evolution of nanoporosities in Cu48Zr47Al5 and Cu45-xZr45Al5Ag5+x using a 0.5 M HF aqueous solution and maintaining a constant holding time of 24 h has been studied. The NPC structure with pores ranging from 50 to 500 nm decorated with nanocubes of Cu2O has been manufactured by dealloying the amorphous Cu48Zr47Al5 alloy. The bimetallic structure NPC/Ag is formed with pores ranging from 10 to 500 nm in the Cu45Zr45Al5Ag5 sample, showing that Cu and Ag do not form a solid solution and the Ag particles precipitate on the surface of interconnected nanopores and form an NPC/Ag composite. A partial dealloying of less noble elements is obtained for the Cu40Zr45Al5Ag10 alloy, which does not form an interconnected network of pores, only some craters with dimensions between 50 nm and 3 µm were obtained. The resulting NPC/Cu2O and NPC/Ag shows an open pore structure and a large surface area. The nanoporous copper synthesized by the dealloying route is suitable for potential applications in catalysis, sensors, etc.

(Invited, Digital Presentation) Formation of Nanostructures and Nanopores By Plasma Deposition and Etching Processes

Plasma processing represents an environmentally friendly, cost efficient and versatile method to modify materials surfaces at low temperatures. Plasma etching processes on polymers, for example, are well studied to enhance the adhesion of coatings and composite materials involving surface nanostructuring. Plasma sputtering is examined to deposit defective metal oxide coatings such as TiO2-x containing oxygen vacancies that are doped by another metal such as Ag. Plasma post-oxidation is applied to tune the nanostructuring of the dopant forming oxidized Ag islets strongly enhancing the catalytic properties to produce reactive oxygen species (ROS). Such coatings can even be functionalized by a plasma polymer cover layer. Non-toxic antimicrobial properties are thus enabled. Plasma polymer deposition with intermittent plasma etching is explored to produce highly nanoporous thin films. Preferential etching of residual hydrocarbons in SiOx layers induces interconnected nanopores in the growing film. Such films allow water diffusion and loading with hydrogels, e.g., as lubricants. Deposition of a nm-thick hydrophobic cover layer finally enables the control of water penetration yielding the nanoconfinement of water molecules that can form a dipolar field. The adsorption of bacteria was found to be affected by the resulting water structuring. Potential biomedical and other technical applications are discussed.

Fabrication of a three-level hierarchically porous silver via GASAR and dealloying processes and its catalytic behavior for formaldehyde oxidation

• Three-level hierarchically porous silver (THPS) are prepared by dealloying GASAR porous Mg 82.43 Ag 17.57 alloy. • Selective dissolution of Mg atoms in α-Mg and Mg 54 Ag 17 forms the submicron- and nano- pores. • Nanopore size and morphology can be controlled by adjusting the variety of dealloying solution. • The THPS-2 sample with fine granular ligaments has better catalytic performance for formaldehyde. Hierarchically porous materials, which have significant potential for applications in catalysis and biotechnology, is limited by complicated synthesis steps and expensive pore-former. Herein, a new type of three-level hierarchically porous silver (THPS) comprises oriented micron pores, submicron pores and inter-connected nanopores was fabricated by dealloying GASAR porous Mg 82.43 Ag 17.57 eutectic alloy. Firstly, the porous Mg 82.43 Ag 17.57 eutectic alloy with micron pore was made by GASAR technique. This porous alloy was then subjected to dealloying treatment, and the submicron pores were gradually formed in the matrix. Meanwhile, the dissolution of Mg atoms and the diffusion and rearrangement of Ag atoms in the acid solutions were resulting in formation of the nanopores. Furthermore, the results of the catalytic performance for formaldehyde showed that those of THPS with granular-like nanopores has better performance, which is attributed to the efficient mass transfer of micron- and submicron pores and the high specific surface area afforded by the nanopores.

Tuneable molecular selective boron nitride nanosheet ultrafiltration lamellar membrane for dye exclusion to remediate the environment.

Smart tuning of the membrane's porous nanostructures offers an effective strategy for creating state-of-the-art, high-performance separation membranes. In aqueous solution, polyethylene glycol (PEG) grafted boron nitride PEGX-g-(f-BN) nanosheets exhibit high permeance and excellent molecular sieving. The molecular selectivity of the PEGX-g-(f-BN) lamellar membrane is controlled by the nanopores, which can be tuned by modulating the interplanar spacing between the nanosheets. Herein, the interplanar spacing of h-BN nanosheets is enhanced in the range of 0.334-0.348nm through grafting different molecular weight PEG. Moreover, the grafted PEG instigates a synergistic effect on the nanosheets in two ways. Firstly, through PEG intercalation, the interlayer spacing of the (002) plane could be adjusted without significant deterioration to the hexagonal crystallographic structure. Secondly, intercalated PEG in BN nanosheets reflects in terms of improved h-BN wettability through transformation to hydrophilic surface characteristics (small contact angle of 36-39°). The fabricated PEGX-g-(f-BN) lamellar membrane acquires stable and interconnected nanopores and nanochannels with an average pore diameter of 1.36-2.19nm. Permeance-exclusion trade-off manipulation through methodical approaches of PEGX-g-(f-BN) decoration thickness and interplanar spacing is exploited to build a better understanding of water transport behavior. PEGX-g-(f-BN) lamellar membranes show unprecedented permeance of ∼1253Lm-2 h-1 bar-1 with a steady methyl blue (MB) exclusion of 98.9% even in different pH conditions.

Multifunctional fish gelatin hydrogel inverse opal films for wound healing

BackgroundWound healing has become a worldwide healthcare issue. Attempts in the area focus on developing patches with the capabilities of avoiding wound infection, promoting tissue remolding, and reporting treatment status that are of great value for wound treatment.ResultsIn this paper, we present a novel inverse opal film (IOF) patch based on a photo-crosslinking fish gelatin hydrogel with the desired features for wound healing and dynamic monitoring. The film with vibrant structure colors was constructed by using the mixture of fish gelatin methacryloyl, chitosan, and polyacrylic acid (PAA) to replicate colloidal crystal templates. As the structures of these natural biomolecules are well-retained during the fabrication, the resultant IOF was with brilliant biocompatibility, low immunogenicity, antibacterial property, as well as with the functions of promoting tissue growth and wound healing. In addition, the IOF presented interconnected nanopores and high specific surface areas for vascular endothelial growth factor loading, which could further improve its angiogenesis capability. More attractively, as the pH-responsive PAA was incorporated, the IOF patch could report the wound healing status through its real-time structural colors or reflectance spectra.ConclusionsThese features implied the practical value of the multifunctional fish gelatin hydrogel IOFs in clinical wound management.Graphical

Developing dual nano/macroporous starch bioaerogels via emulsion templating and supercritical carbon dioxide drying

In this study, emulsified oil droplets were employed as a temporary porogen to obtain dual nano/macroporous starch aerogels by supercritical carbon dioxide (SC-CO2) drying. This method took advantage of the solubility of the oil droplet porogens in acetone, and the insolubility of corn starch in this solvent, so this process could be integrated into the typical aerogel processing method. The effect of porogen content and starch concentration on physical and mechanical properties and the internal morphology of the obtained aerogels were studied. While the neat starch aerogel showed a compact structure in macroscale size with interconnected nanopores, the sacrificing oil droplet porogens induced macropores in the emulsion-templated aerogels. Furthermore, the nanoporous structures of starch aerogels were also well-preserved in which the macropores were surrounded by fine and interconnected nanofibrous networks. It resulted in aerogels that exhibited internal morphology in two scales (macropores and nanopores) with a high surface area (156–190 m2/g).

Mixed matrix membranes containing composite nanosheets with three-dimensional nanopores for efficient CO2 separation

Novel composite nanosheets with three-dimensional (3D) nanopores were used as nanofillers and filled in Pebax® MH 1657 (Pebax) matrix to fabricate mixed matrix membranes (MMMs) for highly efficient CO2/CH4 separation. The nanosheets were formed by anchoring zeolite imidazolate framework-8 (ZIF-8) on the surface of the porous graphitic carbon nitride (g-C3N4). For the composite nanosheets of ZIF-8/g-C3N4, the interconnected 3D nanopores of ZIF-8 on composite nanosheets provided high selective nanochannels in MMMs, thereby improving CO2/CH4 selectivity. Meanwhile, the randomly arranged nanosheets were acted as the ultrafast CO2 transport freeways in MMMs, thus enhancing CO2 permeability. The as-prepared Pebax/ZIF-8/g-C3N4 exhibited an excellent CO2 separation performance. In particular, Pebax/ZIF-8/g-C3N4–9 MMM showed the highest separation performance, which reached 553 ± 23 Barrer and 35.5 ± 0.67 for CO2 permeability and CO2/CH4 separation factor, respectively. The composite nanosheets with 3D nanopores provided an effective strategy to fabricate high-performance MMMs for gas separations.

Multifunctional inverse opal film as a responsive drug carrier for spinal cord injury repair

An excellent drug delivery system is particularly important in trauma repair, especially for chronic hard-healing trauma, such as spinal cord injury (SCI). The SCI is difficult to repair as it is heavily influenced by inflammatory cell infiltration, neuronal axon rupture, and signal transmission interruption. Here, we present a stretched inverse opal film (SIOF) as a responsive drug carrier to deliver fibroblast growth factor 10 (FGF10) and chloroquine phosphate (CQ) for SCI repair. The SIOF was prepared by negatively replicating the silica nanospheres crystal array and was stretched to six times its original length. Benefiting from the elaborate interconnected nanopores of the SIOF, the temperature-sensitive hydrogel can host the black phosphorous quantum dots (BPQDs), and the two drugs (CQ and FGF 10) (Drugs-Gel@SIOF) for SCI repair. The excellent photothermal effect of BPQDs under the near-infrared (NIR) irradiation serves to regulate the release of drugs from the Drugs-Gel@SIOF. Furthermore, the SIOF has high biocompatibility and a special surface topology that orientates cell growth and promotes cytoskeleton elongation. The Drugs-Gel@SIOF showed an excellent effect of inhibiting inflammation and promoting axon growth. The practical performance of the Drugs-Gel@SIOF in promoting the recovery of motor function had been demonstrated by treating the spinal cord trauma rat model. These results indicate that this SIOF is an ideal intelligent delivery system with great potentials in nerve repair.

Ageing behaviour spanning months of NaMt, hectorite and Laponite gels: Surface forces and microstructure – A comprehensive analysis

Recent “artifact-free” microstructure information enabled the development of a more credible model for explaining the ageing time-dependent rheological behavior of NaMt, hectorite and Laponite gels. These gels displayed pronounced ageing behavior lasting months. The platelet morphology and the localised nature of the negative and positive charges produced the essential forces and interaction configurations to form the time-dependent structure. This structure is composed of nano-sized flexible platelets interacting both attractively to form the network junctions and repulsively to open up the structure. These junctions were formed by heterogeneous charge and van der Waals attractions between the jagged and curled edges, and the face of the interacting platelets. The force that is responsible for the time-dependent behaviour is the EDL repulsive force. This force governs the development of the 3-D network structure and drives it towards a minimum free energy state. This process takes a long time to complete. The resultant microstructure is completely interpenetrated with interconnected nanopores trapping as much as 99% of water in volume. At high ionic strength or 0.3 M KCl, the NaMt or bentonite gels became time independent as the van der Waals force formed the structure. The Leong model described the initial ageing behavior well. For the nanodiscotic Laponite gels, the 3-D structure is formed from sheets instead of primarily disks contradicting prevailing model. With the latest microstructure information, new mechanisms were proposed to account for the high yield stress at low solids, low permeability, intercalation behavior, layer stacking and enlarged dried platelets.

An inverse averaging finite element method for solving three-dimensional Poisson-Nernst-Planck equations in nanopore system simulations.

The Poisson-Nernst-Planck (PNP) model plays an important role in simulating nanopore systems. In nanopore simulations, the large-size nanopore system and convection-domination Nernst-Planck (NP) equations will bring convergence difficulties and numerical instability problems. Therefore, we propose an improved finite element method (FEM) with an inverse averaging technique to solve the three-dimensional PNP model, named inverse averaging FEM (IAFEM). At first, the Slotboom variables are introduced aiming at transforming non-symmetric NP equations into self-adjointsecond-order elliptic equations with exponentially behaved coefficients. Then, these exponential coefficients are approximated with their harmonic averages, which are calculated with an inverse averaging technique on every edge of each tetrahedral element in the grid. Our scheme shows good convergence when simulating single or porous nanopore systems. In addition, it is still stable when the NP equations are convection domination. Our method can also guarantee the conservation of computed currents well, which is the advantage that many stabilization schemes do not possess. Our numerical experiments on benchmark problems verify the accuracy and robustness of our scheme. The numerical results also show that the method performs better than the standard FEM when dealing with convection-domination problems. A successful simulation combined with realistic chemical experiments is also presented to illustrate that the IAFEM is still effective for three-dimensional interconnected nanopore systems.

Transformation of Glass Fiber Waste into Mesoporous Zeolite-Like Nanomaterials with Efficient Adsorption of Methylene Blue

Recycling and reusing glass fiber waste (GFW) has become an environmental concern, as the means of disposal are becoming limited as GFW production increases. Therefore, this study developed a novel, cost-effective method to turn GFW into a mesoporous zeolite-like nanomaterial (MZN) that could serve as an environmentally benign adsorbent and efficient remover of methylene blue (MB) from solutions. Using the Taguchi optimizing approach to hydrothermal alkaline activation, we produced analcime with interconnected nanopores of about 11.7 nm. This MZN had a surface area of 166 m2 g−1 and was negatively charged with functional groups that could adsorb MB ranging from pH 2 to 10 and all with excellent capacity at pH 6.0 of the maximum Langmuir adsorption capacity of 132 mg g−1. Moreover, the MZN adsorbed MB exothermically, and the reaction is reversible according to its thermodynamic parameters. In sum, this study indicated that MZN recycled from glass fiber waste is a novel, environmentally friendly means to adsorb cation methylene blue (MB), thus opening a gateway to the design and fabrication of ceramic-zeolite and tourmaline-ceramic balls and ceramic ring-filter media products. In addition, it has environmental applications such as removing cation dyes and trace metal ions from aqueous solutions and recycling water.

The creation of extra storage capacity in nitrogen-doped porous carbon as high-stable potassium-ion battery anodes

Porous carbonaceous materials have been extensively explored as promising anodes for potassium-ion batteries (KIBs), and their potassium storage capacities are always higher than the theoretical specific capacity (279 mA h g−1). However, the mechanism behind the extra capacity for KIBs in porous carbonaceous materials is rarely explored. Herein, we synthesized porous carbonaceous materials with interconnected nanopores modified by abundant edge-doped N atoms to investigate the mechanism for potassium-storage performance. The resulting NPCs-600 displays outstanding electrochemical performances with a high reversible capacity (409 mA h g−1 at 0.1 A g−1 after 200 cycles), excellent rate capability (235 mA h g−1 at 5 A g−1), and remarkable long-term cycling stability (167 mA h g−1 at 5 A g−1 after 10,000 cycles). The remarkable performance results from the nanopores grafted by edge-doped nitrogen atoms on the inner surface which can adsorb more K+ to enhance the capacity of carbon materials beyond K+ intercalation mechanism. Furthermore, the density functional theory (DFT) calculations further demonstrate that nitrogen atoms doped on the edge of defects facilitate to the sorption of K+, providing the extra capacity for KIBs.