Nanoporous Structure Research Articles

Surface Nanostructure Fabrication by Initiated Chemical Vapor Deposition and Its Combined Technologies.

Initiated chemical vapor deposition (iCVD) is a versatile technique that enables the direct growth of nanostructures and surface modification of such structures. Unlike traditional CVD methods, iCVD operates under mild conditions, allowing for damage-free processing of delicate substrates. It can produce highly uniform polymer layers, with thicknesses ranging from over 15 μm to sub-10 nm, conformally coating intricate geometries. The broad range of polymer compositions achievable with iCVD offers precise control of surface chemistry. In this Viewpoint, we present iCVD's mechanisms and the principles for controlling the composition and morphology of deposited layers. We summarize various surface nanostructures including nanodomes, nanocones, nanowrinkles, nanoparticles, and nanoporous structures that are directly fabricated using iCVD. We also demonstrate the integration of iCVD with other advanced methods, such as photo, soft, and nanoimprint lithography; template-assisted growth; and thermal CVD, to leverage the advantages of multiple methods and overcome individual limitations in nanofabrication. Through these combined strategies, we show the iCVD's potential for creating multifunctional nanostructures with broad applications across engineering and biomedical fields.

Aerolysin Nanopore Structures Revealed at High Resolution in a Lipid Environment.

Aerolysin is a β-pore-forming toxin produced by most Aeromonas bacteria, which has attracted large attention in the field of nanopore sensing due to its narrow and charged pore lumen. Structurally similar proteins, belonging to the aerolysin-like family, are present throughout all kingdoms of life, but very few of them have been structurally characterized in a lipid environment. Here, we present the first high-resolution atomic cryo-EM structures of aerolysin prepore and pore in a membrane-like environment. These structures allow the identification of key interactions, which are relevant for understanding the pore formation mechanism and for correctly positioning the pore β-barrel and its anchoring β-turn motif in the membrane. Moreover, we elucidate at high resolution the architecture of key pore mutations and precisely identify four constriction rings in the pore lumen that are highly relevant for nanopore sensing experiments.

Nanoporous high-entropy alloys and metallic glasses: advanced electrocatalytic materials for electrochemical water splitting.

Electrochemical water splitting is a promising approach to convert renewable energy into hydrogen energy and is beneficial for alleviating environmental pollution and energy crises, and is considered a clean method to achieve dual-carbon goals. Electrocatalysts can effectively reduce the reaction energy barrier and improve reaction efficiency. However, designing electrocatalysts with high activity and stability still faces significant challenges, which are closely related to the structure and electronic configuration of catalysts. Nanoporous high-entropy alloys (np-HEAs) and metallic glasses (np-MGs), characterized by long-range chemical disorder intertwined with local chemical order combined with three-dimensional, interconnected nanoporous structure, exhibit distinctive electrocatalytic properties and application potential for electrochemical water splitting. To promote the widespread application of np-HEAs and np-MGs, it is of great significance to rationally design and apply them in the field of electrolytic water splitting. In this review, the basic principles of hydrogen evolution reaction and oxygen evolution reaction as well as the fabrication techniques of np-HEAs and np-MGs are introduced. The recent progress in the efficient application of np-HEAs and np-MGs in electrochemical water splitting, and the current challenges and prospects are summarized. This review will provide theoretical guidance for the development of np-HEAs and np-MGs in electrochemical water splitting applications.

Solid-State Precipitation of Silver Nanoparticles Nucleated during Al Anodizing: Mechanism and Antibacterial Properties.

This study presents an innovative approach to creating antibacterial aluminum surfaces by combining the antibacterial properties of silver nanoparticles (Ag NPs) with the nanoarchitecture of anodized aluminum oxide in one step. An Al-Ag alloy containing 10 wt % Ag was synthesized and anodized in 0.3 M oxalic acid. Ag NPs precipitated in the solid state during anodization, resulting in a porous nanocomposite structure. Comprehensive characterization using SEM, TEM, and EDS revealed a 43 μm thick oxide layer with uniformly distributed nanopores of approximately 100 nm in diameter. Ag NPs with diameters ranging from 2 to 14 nm precipitated dispersed on the surface, inside pores, and within the Al2O3 matrix. Antibacterial properties were evaluated against Escherichia coli. The anodized Al-Ag surface demonstrated robust antibacterial activity after short incubation times (up to 1 × 108 CFU/ml after 3 h). The enhanced antibacterial properties are attributed to the optimal size and distribution of Ag NPs and the potential physical bactericidal effect of the nanoporous structure. This strategy for the precipitation of Ag NPs in the solid state could be used to fabricate high-touch surfaces in hospitals.

Chemical Redox Agent-Driven Noncorrosive Formation of Nanoporous Mg Structures for Advanced Hydrogen Storage.

Light metal-based nanomaterials are widely used for energy storage due to their high energy density and surface-to-volume ratio. However, their high reactivity is paradoxically both the source of advantageous properties and a hurdle to the fabrication of stable nanostructures. Here, we demonstrate the formation of nanoporous Mg via chemical redox agent-driven dealloying, which ensures minimized surface passivation and results in fine nanostructures with <50 nm of interconnected metallic ligament despite the labile chemical properties of Mg. The thin passivation layer protects the metallic ligaments from severe coarsening by suppressing surface diffusion. The hydrogen storage performance of nanoporous Mg is investigated as an exemplar for energy applications, and the hydrogen ab/desorption kinetics is substantially enhanced compared to other nano-Mg with similar dimensions. Mesoscale simulations highlight the significance of the bicontinuous structure compared to the particle-like counterpart. This work offers valuable insights into the unexplored realm of reactive metal-based nanoporous structures, highlighting their potential for sustainable energy storage and carrier media.

Nanomaterials for Zinc Batteries—Aerogels

Aqueous zinc batteries, mainly including Zn-ion batteries (ZIBs) and Zn–air batteries (ZABs), are promising energy storage systems, but challenges exist at their current stage. For instance, the zinc anode in aqueous electrolyte is impacted by anodic dendrites, hydrogen and oxygen precipitation, and some other harmful side reactions, which severely affect the battery’s lifespan. As for traditional cathode materials in ZIBs, low electrical conductivity, slow Zn2+ ion migration, and easy collapse of the crystal structure during ion embedding and migration bring challenges. Also, the slower critical oxygen reduction reaction (ORR), for example, in ZABs shows unsatisfactory results. All these issues greatly hindered the development of zinc batteries. Aerogel materials, characterized by their high specific surface area, unique open-pore structure formed by nanoporous structures, and excellent physicochemical properties, have a positive role in cathode modification, electrode protection, and catalytic reactions in zinc batteries. This manuscript provides a systematic review of aerogel materials, highlighting advancements in their preparation and application for zinc batteries, aiming to promote the future progress and development of aerogel nanomaterials and zinc batteries.

Programmable Porous Silicon Microparticles for Temporally Staged Drug Delivery in Combination Cancer Immunotherapy.

Combination therapies using checkpoint inhibitors with immunostimulatory agonists have attracted great attention due to their synergistic therapeutic effects for cancer treatment. However, such combination immunotherapies require specific timing of doses to show sufficient antitumor efficacy. Sequential treatment usually requires multiple administrations of the individual drugs at specific time points, thus increasing the complexity of the drug regimen and compromising patient compliance. Here, we introduce an injectable porous silicon microparticle (pSiMP) for combination cancer immunotherapy where its multilayered nanopore structure was electrochemically programmed to achieve release of three distinct immunomodulatory drugs in the right sequence at the desired time. We find the optimal sequential treatment timeline of stimulator of interferon genes (STING) agonist, anti-OX40 antibody (aOX40), and anti-PD-1 antibody (aPD-1) for immunosuppressive tumors. We show that a single intratumoral injection of a cocktail of release-programmed pSiMPs coloaded with each antibody and a STING agonist significantly suppresses the tumor growth compared to conventional treatment involving sequential bolus injections, or an injection of pSiMPs configured to release all drugs at the same time, with no delay. With the timely release of immunomodulatory drugs, the programmable pSiMPs offer an effective treatment strategy for combination immunotherapy.

Bioactive Silk Cryogel Dressing with Multiple Physical Cues to Control Cell Migration and Wound Regeneration.

Introducing multiple physical cues to control cell behaviors effectively is considered as a promising strategy in developing bioactive wound dressings. Silk nanofiber-based cryogels are developed to favor angiogenesis and tissue regeneration through tuning hydrated state, microporous structure, and mechanical property, but remained a challenge to endow with more physical cues. Here, β-sheet rich silk nanofibers are used to develop cryogels with nanopore structure. Through optimizing crosslinking time and exposing the reactive group inside the nanofibers, the crosslinking reaction is improved to induce stable cryogel formation. Besides the hydrated state and macroporous structure, the nanopore structure formed on the macroporous walls, providing hierarchical microstructures to improve cell migration. Both in vitro and in vivo results reveal quicker cell migration inside the cryogels, which then accelerates angiogenesis and wound healing. The mechanical properties can further regulate to match with skin regeneration. The wound healing study in vivo reveals lower inflammatory factor secretion in the wounds treated with softer cryogels with nanopores, which then resulted in the best angiogenesis and wound healing with less scar. Therefore, the porous cryogels with multiple physical cues can be fabricated with silk nanofibers to control cell behaviors and tissue regeneration, providing a promising approach for designing bioactive wound dressings.

Applications of Nanomaterial Coatings in Solid-Phase Microextraction (SPME)

This review explores the advances in developing adsorbent materials for solid-phase microextraction (SPME), focusing on nanoparticles, nanocomposites, and nanoporous structures. Nanoparticles, including those of metals (e.g., gold, silver), metal oxides (e.g., TiO2, ZnO), and carbon-based materials (e.g., carbon nanotubes, graphene), offer enhanced surface area, improved extraction efficiency, and increased selectivity compared to traditional coatings. Nanocomposites, such as those combining metal oxides with polymers or carbon-based materials, exhibit synergistic properties, further improving extraction performance. Nanoporous materials, including metal–organic frameworks (MOFs) and ordered mesoporous carbons, provide high surface area and tunable pore structures, enabling selective adsorption of analytes. These advanced materials have been successfully applied to various analytes, including volatile organic compounds (VOCs), polycyclic aromatic hydrocarbons (PAHs), pesticides, and heavy metals, demonstrating improved sensitivity, selectivity, and reproducibility compared to conventional SPME fibers. The incorporation of nanomaterials has significantly expanded the scope and applicability of SPME, enabling the analysis of trace-level analytes in complex matrices. This review highlights the significant potential of nanomaterials in revolutionizing SPME technology, offering new possibilities for sensitive and selective analysis in environmental monitoring, food safety, and other critical applications.

Smart Bioelectronic Nanomesh Face Masks with Permeability and Flexibility for Monitoring Cortisol in Saliva.

Bioelectronic face masks can easily collect biomarkers in saliva, in which free cortisol is abundant. However, conventional bioelectronic face masks involve significant challenges in terms of permeability and inhalation due to their nonpermeable film-type structure. Herein, we introduce a flexible and permeable nanomesh-based wearable biosensor designed for bioelectronic face masks that monitor cortisol levels. The diameter of the nanofiber matrix has a range of 200 to 500 nm and offers outstanding flexibility (2% resistance change at a bending radius of 2 mm), reliability (0.3% resistance change at a bending radius of 5 mm after 1000 bending cycles), and permeability (116.91 g m-2 h-1 at 18 °C with 40% humidity, which is 10 times higher compared with film) based on the nanoporous structure. We evaluated the electrochemical responses of functionalized interdigitated electrodes on a flexible and permeable poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) nanomesh. Our nanomesh cortisol biosensors demonstrated exceptional sensitivity to cortisol, even at low concentrations, with a detection limit as low as 10 pM. Furthermore, we measured cortisol in clinical samples, such as artificial saliva and human saliva, using nanomesh-based bioelectronic face masks. This study highlights the potential for further applications of bioelectronic face masks for detecting numerous biomarkers.

HRTEM Study of Desulfurization of Pt- and Pd-Rich Sulfides from New Caledonia Ophiolite

Oxygen-bearing platinum group minerals (O-bearing PGMs) are intergrown with base metal sulfides (BMS, e.g., pentlandite–[NiFe]9S8) within fractures in chromite grains from chromitite bodies on Ouen Island, New Caledonia. These PGMs are hosted in chlorite and serpentine, which formed during serpentinization of olivine and pyroxene. The O-bearing PGM grains are polygonal, show microfracturing (indicating volume loss), and contain Pt-Pd-rich sulfide remnants, suggesting pseudomorphic replacement of primary (magmatic) sulfides. They display chemical zonation, with Pt(-Pd-Ni-Fe) relict sulfide cores replaced by Pt-Fe-Ni oxidized alloy mantles and Pt-Cu-Fe(-Pd) alloy rims (tulameenite), indicating desulfurization. The core and mantle show a nanoporous structure, interpreted as the result of coupled dissolution–reprecipitation reactions between magmatic sulfides and low fO2–fS2 serpentinite-related fluids, probably formed during olivine transformation to serpentine + magnetite (early stages of serpentinization). This fluid infiltrated magmatic sulfides (PGE-rich and BMS), degrading them to secondary products and releasing S and metals that were accommodated in the mantle and rim of O-bearing PGMs. Upon olivine exhaustion, an increase in fO2 might have stabilized Pt-Fe-O compounds (likely Pt0/Pt-Fe + Fe oxyhydroxides) alongside Ni-Fe alloys. Our results show that post-magmatic desulfurization of primary sulfides produces complex nano-scale intergrowths, mainly driven by changes in the fluid’s physicochemical properties during serpentinization.

In situ synthesis of spatially hierarchically porous SnO2 nanostructures as efficient ethanol sensors: Unveiling porosity and support effect

Porous SnO2 nanostructures have garnered tremendous attention for detecting volatile organic compounds due to their high surface area, oxygen vacancies, and massive adsorption and diffusion sites for gases. However, the effect of porosity and support on the ethanol-sensing behavior of SnO2 still needs to be clarified. Herein, porous SnO2 nanostructures supported on reduced graphene (SnO2/rGO) were synthesized via the hydrothermal method, followed by annealing at different temperatures under air. The hydrothermal method with annealing at 500 °C endowed the formation of spatial hierarchical porous SnO2 microspheres (HMP-SnO2-500) composed of small nanoflakes, but at 300 °C, aggregated microspheres with less porosity (HMP-SnO2-300) were formed, and hydrothermal alone yielded aggregated flakes on rGO nanosheets (SnO2/rGO). The porosity and crystallinity of SnO2 improved significantly after annealing at 500 °C under air, and the particle size also decreased. Thereby, the ethanol sensing properties of HMP-SnO2-500 were higher than those of HMP-SnO2-300, SnO2/rGO, and SnO2, with a detection limit of 0–3000 ppm, a quick response time of 5–20 s, fast recovery, long-term durability (12 days), and outstanding sensitivity in the presence of different volatile organic materials. This is due to the hierarchical porosity, high surface area, higher electrical conductivity, and synergetic effect of HMP-SnO2-500, which may open new gates for the rational design of self-standing or supported porous SnO2 nanostructures for efficient sensing of organic materials.

Nafion coated nanopore electrode for improving electrochemical aptamer-based biosensing.

The transition to a personalized point-of-care model in medicine will fundamentally change the way medicine is practiced, leading to better patient care. Electrochemical biosensors based on structure-switching aptamers can contribute to this medical revolution due to the feasibility and convenience of selecting aptamers for specific targets. Recent studies have reported that nanostructured electrodes can enhance the signals of aptamer-based biosensors. However, miniaturized systems and body fluid environments pose challenges such as signal-to-noise ratio reduction and biofouling. To address these issues, researchers have proposed various electrode coating materials, including zwitterionic materials, biocompatible polymers and hybrid membranes. Nafion, a commonly used ion exchange membrane, is known for its excellent permselectivity and anti-biofouling properties, making it a suitable choice for biosensor systems. However, the performance and mechanism of Nafion-coated aptamer-based biosensor systems have not been thoroughly studied. In this work, we present a Nafion-coated gold nanoporous electrode, which excludes Nafion from the nanoporous structures and allows the aptamers immobilized inside the nanopores to freely detect chosen targets. The nanopore electrode is formed by a sputtering and dealloying process, resulting in a pore size in tens of nanometers. The biosensor is optimized by adjusting the electrochemical measurement parameters, aptamer density, Nafion thickness and nanopore size. Furthermore, we propose an explanation for the unusual signaling behavior of the aptamers confined within the nanoporous structures. This work provides a generalizable platform to investigate membrane-coated aptamer-based biosensors.

Regulating Zn deposition via an ion-sieving, nanoporous cellulose separator for high performance aqueous zinc-ion batteries.

Aqueous zinc-ion batteries (AZIBs), one of the most promising renewable energy storage devices, are largely impeded by the disreputable cycling stability in its large-scale application as a result of the undesirable Zn dendrites growth and the side reactions. In this context, a carboxylate (-COO-) anionic group functionalized cellulose nanofibrils separator (A-CNF) with nanoporous structure and ion-sieving effect is developed to realize a stable Zn anode without dendrites and by-products. An increased Zn2+ transference number and uniform Zn deposition can be achieved through the electrostatic adsorption between -COO- and Zn2+. More importantly, the synergistic effect between -COO- and hydroxyl group (-OH) in the cellulose nanofibrils separator inhibits the occurrence of side reactions caused by SO42- and free water molecules. As a result, the nanoporous separator consisting of carboxylated cellulose nanofibrils enables Zn anode with high stability and utilization, exhibiting a stable cycling life for 950 h in Zn//Zn cell and an admirable coulombic efficiency of 98.9 % after 300 cycles in Zn//Cu cell. The assembled Zn//MnO2 full cell with the nanoporous cellulose nanofibrils-based separator shows exceptional cyclability and capacity retention after 1000 cycles. This work provides a valuable and practical separator for high performance AZIBs, which might spur its practical application.

Deep eutectic solvent-enabled lignocellulosic biomass valorization: Toward understanding of biomass pretreatment, lignin dissolution, and lignin's antioxidant activity.

A comprehensive study was conducted to determine the effects of water and ethylene glycol (EG) on biomass pretreatment using a binary deep eutectic solvent (DES) containing choline chloride and acetic acid (1ChCl3AC) at a mole ratio of 1:3. Different quantities of water and EG were combined with 1ChCl3AC to pretreat wheat straw, miscanthus, eucalyptus, and sorghum stalk at 130°C for 6h. The changes in nanopore structure and surface roughness of wet biomass, as well as biomass crystallinity after 1ChCl3AC-based pretreatment were investigated using XRD and small-angle neutron scattering (SANS). Adding a certain amount of water or EG did not reduce the delignification ratio or saccharification rate. Furthermore, SANS was used to explore the interactions between lignin, 1ChCl3AC, and water. The study found that lignin molecules produced various nanostructures through hydrogen bond, π-π, and hydrophobic interactions in 1ChCl3AC and its aqueous solutions. Following pretreatment, lignins were extracted and fractionated with three organic solvents to minimize structural heterogeneity. A collection of lignin antioxidants with varying activities was obtained, and antioxidant activity assessments revealed three distinct interactions amongst binary lignin combinations. The findings of this study add to our understanding of the interplay of 1ChCl3AC, water, EG, and lignin.

Effect of polishing on the morphology of Zircaloy-4 nanostructure: formation of a novel hexagonal nanoscale pattern.

Zircaloy-4 (Zr-4) is widely used as the cladding material in nuclear power plants (NPPs) due to its excellent corrosion resistance and low neutron absorption cross-section. Under Loss of Coolant Accident (LOCA) conditions, oxidation of Zr-4 can compromise the safety of the NPPs by accelerating hydrogen production. Therefore, enhancing the oxidation resistance of Zr-4 is a critical research focus. Surface modification through a facile method offers a promising approach to address this issue. This study explores the impact of chemical, mechanical, and electropolishing (EP) pre-treatments on Zr-4 morphology before and after anodization. EP conducted in ethylene glycol monobutyl ether-perchloric acid electrolyte produced a mirror-like surface finish with hexagonal nanopattern formation under optimized conditions, as revealed by SEM studies. Anodization of the patterned surface in a glycerol-based electrolyte resulted in a hybrid (nanoporous and nanotubular) structure, unlike the nanotubular-only morphology observed in the chemically or mechanically polished samples. EDAX and XRD analyses confirmed the formation of ZrO2. The hexagonal nanopattern generated by EP suppressed the dissolution of the nanotube during anodization, resulting in a hybrid nanostructure. Additionally, the chemical polishing of EP-treated Zr-4 in HF : HNO3 : H2O generated a porous particulate structure due to selective etching. This work demonstrates that the surface pre-treatment significantly influences the morphology of anodized Zr-4 nanostructures and suggests the potential use of EP in other materials for hexagonal nanopattern generation.

Exploring the diffusion of DNA strands into nanoporous structures for establishing a universal electrochemical biosensor.

The development of universal electrochemical sensing platforms with high sensitivity and specificity is of great significance for advancing practical disease diagnostic methods and devices. Exploring the structural properties of electrode materials and their interaction with biomolecules is essential to developing novel and distinctive analytical approaches. Here, we innovatively investigated the effect of DNA length and configuration on DNA molecule transfer into the nanostructure of a nanoporous gold (NPG) electrode. The NPG electrode can not only distinguish and quantify short DNA strands but can also prevent the diffusion of long DNA, thereby minimizing or eliminating background interference. Leveraging these findings, we developed a universal DNA-based NPG electrochemical biosensing platform for the detection of different types of biomolecules. As a proof-of-concept, this sensing platform was integrated with nuclease-assisted target-recycling recognition and amplification reactions to achieve sensitive and specific detection of single-stranded DNA, microRNA-21, and carcino-embryonic antigen, with detection limits of 4.09, 27.4, and 0.28 fM, respectively. The demonstrated universality, sensitivity, specificity, and capability for analyzing complex samples ensure a comprehensive and robust detection approach for nucleic acid-based molecular diagnosis.

Synthesis of three-dimensional Co3O4–carbon composite electrode materials with nanoporous structure for high-energy density supercapacitors

Synthesis of three-dimensional Co3O4–carbon composite electrode materials with nanoporous structure for high-energy density supercapacitors

Formation of Si-based nanoporous structures on AlSi10Mg manufactured by selective laser melting

Formation of Si-based nanoporous structures on AlSi10Mg manufactured by selective laser melting

Interfacial Constructing Poly(ionic liquids) on Nanoporous Block Copolymers for Antifouling Ultrafiltration.

The remarkable flexibility in structural tunability and designability of poly(ionic liquids) (PILs) has garnered significant attention. Integration of PILs with membranes, novel properties, and functionalities is anticipated for applications in the fields of membrane separation. Here, we develop a facile method to prepare PIL-functionalized membranes in a one-step process by combining selective swelling-induced pore generation and ionic liquid functionalization. The block copolymer of poly(2-dimethylaminoethyl methacrylate)-block-polystyrene (PDMAEMA-b-PS, abbreviated as SDMA) films is immersed in a mixture of ethanol and bromopropane. In addition to the formation of nanoporous structures, an interfacial quaternization reaction between the PDMAEMA blocks and bromopropane occurs to generate poly(methacrylatoethyl propyl dimethylammonium bromide), resulting in the PIL-Br-functionalized membrane (SIL-Br) during the swelling process. It is noteworthy that bromopropane acting as a reactant also promotes the process of selective swelling. The water permeability of the resulting SIL-Br membrane is several times higher than that of the SDMA membrane, which is attributed to the increased pore size and significantly higher hydrophilicity of the SIL-Br membrane. In addition, the anion exchange of SIL-Br with l-proline (l-Pro) readily forms SIL-Pro-functionalized membranes (SIL-Pro), which exhibit exceptional electrical neutrality. Antifouling tests demonstrate that both SIL-Br and SIL-Pro have excellent resistance to proteins compared to the non-PIL-functionalization SDMA membrane, implying their great potential as antifouling membranes for water treatment.