Nano-sized Channels Research Articles

Fabrication of switchable biocompatible, nano-fluidic devices using a thermoresponsive polymer on nano-patterned surfaces

In this study, a method for depositing and patterning the thermosensitive polymer poly(N-isopropylacrylamide) on SiO2 surfaces is presented for potential use in nano-sized microfluidic channels. Two approaches based on nanolithographic processes are shown for this purpose. In both cases, a self-assembling monolayer consisting of (3-aminopropyl)-dimethylethoxysilane was bound to the hydroxyl group of the substrate surface and subsequently functionalized with the polymerization initiator α-bromoisobutyryl bromide. In the first approach the silane monolayer itself was patterned using a photoresist and a lift-off process, followed by the selective deposition of the initiator, which starts a substrate-induced atom transfer radical polymerization for the growth of polymer on the silane monolayer. In the second approach, the lift-off takes place after the polymerization on the substrate surface. The result of this study shows the successful application of the process steps for the nano-dimensioned grafting of poly(N-isopropylacrylamide) onto SiO2 substrates. The reaction time of the silane monolayer with the polymerization initiator and the composition of the reaction solution used were found to have the greatest influence of the processes. AFM and XPS analysis of the functionalized surfaces revealed patterned growth of both the self-assembling monolayer and the polymer structures.

Confined electric field in nano-sized channels of ionic porous framework towards unique adsorption selectivity

Confined electric field in nano-sized channels of ionic porous framework towards unique adsorption selectivity

Bioactive glass–ceramics containing fluorapatite, xonotlite, cuspidine and wollastonite form apatite faster than their corresponding glasses

Crystallisation of bioactive glasses has been claimed to negatively affect the ion release from bioactive glasses. Here, we compare ion release and mineralisation in Tris–HCl buffer solution for a series of glass–ceramics and their parent glasses in the system SiO2–CaO–P2O5–CaF2. Time-resolved X-ray diffraction analysis of glass–ceramic degradation, including quantification of crystal fractions by full pattern refinement, show that the glass–ceramics precipitated apatite faster than the corresponding glasses, in agreement with faster ion release from the glass–ceramics. Imaging by transmission electron microscopy and X-ray nano-computed tomography suggest that this accelerated degradation may be caused by the presence of nano-sized channels along the internal crystal/glassy matrix interfaces. In addition, the presence of crystalline fluorapatite in the glass–ceramics facilitated apatite nucleation and crystallisation during immersion. These results suggest that the popular view of bioactive glass crystallisation being a disadvantage for degradation, apatite formation and, subsequently, bioactivity may depend on the actual system study and, thus, has to be reconsidered.

Water molecules in boron nitride interlayer space: ice and hydrolysis in super confinement.

Development of nano-sized channels and filters in the recent years has made the role of water immensely important as water molecules affect their performance and durability. Here, we take advantage of molecular dynamics and density functional theory methods to demonstrate the shift in behavior of water molecules confined between hexagonal boron nitride (HBN) sheets spaced at 3.0 to 6.5 Å. Our results demonstrate that lower interlayer spaces cause higher amounts of charge transferred between the species, while at extreme degrees of confinement, these interactions cause the disintegration of trapped water molecules. Consequently, the inner face of the HBN sheets is functionalized with hydroxyl groups, releasing hydrogens in the form of protons that travel the interlayer space by Grotthuss mechanism. This is the first-hand evidence of a mechanical form of hydrolysis that corresponds with a nucleophilic attack (on boron atoms) to relieve water from extreme confined conditions. This process unveils a previously unknown behavior of water within extremely confined spaces and reveals new considerations concerning nanofilters and nanochannels.

Bridging adsorption behavior of confined CH[formula omitted]-CO[formula omitted] binary mixtures across scales

An accurate understanding of the competitive adsorption of CH4-CO2 binary mixtures in nano-confined systems is critical for engineering CO2 storage in shale gas reservoirs. Due to difficulties in making reliable experimental observations in nano-scale, atomistic simulations (ASs), such as the Grand Canonical Monte Carlo (GCMC) method, provide a viable approach to studying the adsorption behavior of confined fluids. ASs are, however, limited in the size of the compositional domain due to the high computational cost. This work proposes a framework that combines AS and the lattice Boltzmann (LB) method to bridge the physics of confined fluids across scales. The Peng–Robinson equation of state (PR-EoS) produces fugacity coefficients, which serve as input for conducting multi-component GCMC simulations. These GCMC simulations explore the competitive adsorption behavior of CH4-CO2 in nano-slits at various composition, pressure, and channel-width conditions. Both components generate adsorption layers with high densities near the walls with CO2 preferentially adsorbing compared to CH4 on the organic walls of carbon sheets. At the mesoscale, a pseudopotential model represents the intermolecular forces in multi-component, multiple-relaxation-time LB simulations. The LB simulations are in good agreement with the GCMC results, allowing us to obtain values for tunable LB parameters. We then extend the use of LB to simulate adsorption behavior in complex networks with nano-sized channels. The phase behavior and fluid properties in the complex geometries of nano-channels differ from nano-slits and bulk systems. The bridging of physics from GCMC (microscale) to LB (mesoscale) via the macroscale PR-EoS connects the adsorption behavior of binary systems across scales.

Studies on application of Petcoke-based graphene membranes for CO2 separation

ABSTRACT Graphene-based separation membranes exhibit high separation potential to separate ions and molecules by the interlayer spacing with high surface area, porosity and tunable nanosized channels. The large-scale manufacturing of graphene-based membranes for gas separation is limited and challenging. Deposition of uniform, and selective ultrathin films as membrane is a big challenge for scalable separation with existing methods. In present study, solvent-ink-jet printing technique is applied for dispersing and uniform coating of graphene layers onto the membrane support. Preparation of graphene-based ink is the core objective of the operation for evaluating stability, coating and followed by separation studies. As prepared, graphene ink is filled in the cartridge of HP Desk-Jet-1110 series, which is available and slightly modified for the printing on the RO-membrane as support. The prepared membranes are characterized and analyzed for gas separation performance study. The decrease in gas composition of CO2 in permeate is observed and around 93% ± 0.5 of CO2 is separated from the gaseous mixtures.

Nanochannel Electro-Injection as a Versatile Platform for Efficient RNA/DNA Programming on Dendritic Cells.

The utilization of dendritic cell (DC) vaccines is a promising approach in cancer immunotherapy, and the modification of DCs for the expression of tumor-associated antigens is critical for successful cancer immunotherapy. A safe and efficient method for delivering DNA/RNA into DCs without inducing maturation is beneficial to achieve successful DC transformation for cell vaccine applications, yet remains challenging. This work presents a nanochannel electro-injection (NEI) system for the safe and efficient delivery of a variety of nucleic acid molecules into DCs. The device is based on track-etched nanochannel membrane as key components, where the nano-sized channels localize the electric field on the cell membrane, enabling lower voltage (<30V) for cell electroporation. The pulse conditions of NEI are examined so that the transfection efficiency (>70%) and biosafety (viability >85%) on delivering fluorescent dyes, plasmid DNA, messenger RNA, and circular RNA (circRNA) into DC2.4 are optimized. Primary mouse bone marrow DC can also be transfected with circRNA with 68.3% efficiency, but without remarkably affecting cellular viability or inducing DC maturation. These results suggest that NEI can be a safe and efficient transfection platform for in vitro transformation of DCs and possesses a promising potential for developing DC vaccines against cancer.

Nano-Sized Channels Resulting from the Packing of Discrete 3d–4f Metal Complexes in Crystals

Nano-Sized Channels Resulting from the Packing of Discrete 3d–4f Metal Complexes in Crystals

De novo design of peptides that form transmembrane barrel pores killing antibiotic resistant bacteria.

De novo design of peptides that self-assemble into transmembrane barrel-like nanopores is challenging due to the complexity of several competing interactions involving peptides, lipids, water, and ions. We have develop a computational approach for the de novo design of α-helical peptides that self-assemble into stable transmembrane barrel pores with a central nano-sized functional channel. We formulate the previously missing design guidelines and report 52 sequence patterns that can be tuned for specific applications using the identified role of each residue. Atomic force microscopy, fluorescent dye leakage, and cryo-EM experiments confirm that the designed peptides form leaky membrane nanopores in vitro. Customized designed peptides act as antimicrobial agents able to kill even antibiotic-resistant ESKAPE bacteria at micromolar concentrations, while exhibiting low toxicity to human cells. The peptides and their assembled nanopore structures can be similarly fine-tuned for other medical and biotechnological applications.

The effect of temperature and external force on the thermal behavior of oil-based refrigerant inside a nanochannel using molecular dynamics simulation

Heat transfer (HT) has always been one of the major challenges in engineering. Many approaches have been offered to enhance or control HT. One of the common techniques to develop the thermal performance of devices is to use nano-sized channels. This study is aimed to examine the influence of temperature and external force (EF) on nanochannel simulated samples by molecular dynamics simulation (MDS). The present study examined the effect of initial temperature (300–400 K) and EF (with 0.001–0.01 eV/Å) on oil inside the nanochannel. The results show that increasing temperatures up to 350 K increases the heat flux (HF) and thermal conductivity (TC) increase and decreases due to the increased number and intensity of atomic collisions in the structures. The HF and TC at 350 K are 946 W/m2 and 0.66 W/m.K. Also, by changing the EF from 0.001 to 0.01 eV/Å, the HF increases from 911 to 942 W/m2 and the TC by 0.52 to 0.63 W/m.K. So, with anincrement in EF, oscillation amplitude increases, and thermal performance improves. Since the thermal performance of refrigerant is noticeable in various industrial applications, it’s hopeful this study proposed an optimal mechanism in practical samples.

Nano-channel confined biomimetic nanozyme/bioenzyme cascade reaction for long-lasting and intensive chemiluminescence

We present here a novel nano-channel confined biomimetic nanozyme/bioenzyme system, which is prepared by co-immobilizing polyoxometalates (vanadomolybdophosphoric heteropoly acid, PMoV2) and glucose oxidase (GOx) in the nano-scale channel of core-shell mesoporous silica (CSMS) microspheres. The biomimetic dual-enzyme nanoreactors (CSMS@PMoV2@GOx) is used for producing long-lasting chemiluminescence (CL) emission. With glucose and luminol in the reaction mixture, hydrogen peroxide (H2O2) is formed in mesoporous channels by GOx catalysis and then is consumed immediately by PMoV2 to induce CL emission. Confined in nano-size channels of CSMS materials, the biomimetic cascade reactions can induce a long-lasting CL emission with a flat period over 12 h. The proposed CSMS@PMoV2@GOx system has excellent reproducibility and storage stability, and has been applied for glucose sensing in human serum samples with satisfactory accuracy. Our study provides a new glow-type CL system based on nanozyme/bioenzyme cascade reactions confined in nano-scale channels of CSMS microspheres, and will also shed a light on potential application of functional polyoxometalates immobilized in mesoporous materials, which would be of great value in various fields including bioassays and heterogeneous catalysis.

Densely functionalized proton exchange membrane from sulfonated poly(aryl ether ketone) containing multiple flexible side chains for fuel cell

Proton exchange membranes play a pivotal role in boosting the efficiency of fuel cells and hence focused research in this area is highly desirable. Here we report that a series of poly(aryl ether ketone)s with amino and trifluoromethyl units (AFPAEK) were synthesized by nucleophilic substitution polycondensation. Subsequently, sulfonated poly(aryl ether ketone) (SAFPAEK) membranes were prepared with amino groups of AFPAEKs as reaction sites to densely graft alkyl sulfonate side chains. This special structure of hydrophilic backbone containing trifluoromethyl groups and hydrophilic sulfonic acid groups generated nano-sized proton channels. The facilitated transportation of protons and cations through these membranes enables the prepared membranes to obtain high IEC and desirable proton conductivity. In particular, the SAFPAEK-50 membrane exhibits high proton conductivity from 0.077 to 0.179 S cm−1, which is higher than that of Nafion 115 over the entire temperature range. Meanwhile, SAFPAEK membranes possess excellent mechanical properties and favorable stability (thermal stability and oxidation stability). Importantly, SAFPAEK-50 displays a peak power density of 70.9 mW cm−2 at 158.8 mA cm−2 in a direct borohydride‑hydrogen peroxide fuel cell, which is higher than that of Nafion 115 (60.9 mW cm−2 at 151.2 mA cm−2). Therefore, the results reveal that the prepared densely functionalized membranes become good candidate proton exchange membrane materials for evaluation in fuel cell applications.

Printed graphene oxide-based membranes for gas separation and carbon capture

Graphene oxide (GO)-based separation membranes have demonstrated the great potential to separate molecules and ions by the interlayer spacing with tunable nano-sized channels. The scalable fabrication of GO-based gas separation membranes, however, remains challenging, although a few preparation approaches have been reported. In this work, we present for the first time that the co-solvent ink-jet printing, as a fast and scalable method, can be utilized for scalable GO-based gas separation membrane preparation. Large-area (>100 cm2), ultrathin, and high-quality GO membrane was successfully deposited on commercial polysulfone (PS) support, and characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction, et al., Selective hydrogen (H2) and helium (He) transport over carbon dioxide (CO2) and nitrogen (N2) was demonstrated for the printed GO membrane. To further explore the separation potential of the printed GO-based gas membrane, additives for facilitated molecular transport were incorporated during the membrane printing process. By inserting CO2-philic agents into the printed GO membrane, highly efficient separation of CO2 from N2 was achieved with CO2/N2 selectivity of 70 and CO2 permeance as high as 2,500 GPU. The strategy proposed here may provide guidance for large-scale GO-based gas separation membrane production and a versatile approach for applying other functional 2-dimensional materials towards the membrane separation application.

Carbonized cattle manure-based photothermal evaporator with hierarchically bimodal pores for solar desalination in high-salinity brines

Interfacial solar desalination shows great promise to become an alternative technique for freshwater generation. However, the unavoidable fouling undermines continuous evaporation because the accumulated salt crystals weaken sunlight absorption and salt drainage, especially in high-salinity brines. Therefore, developing a photothermal evaporator with excellent salt rejection capability is urgent for high-salinity solar desalination. Here, a carbonized cattle manure-based photothermal evaporator with hierarchically bimodal pores is validated as an efficient desalinator for high-salinity brine (≥15 wt%). Taking advantage of the bimodally porous structure and interconnected microchannels formed by carbon fiber networks, it realizes rapid water transportation and quickly replenishes the surface-desalinated brine to prevent salt accumulation and enable stable freshwater generation. This carbonized manure evaporation device demonstrates a rapid evaporation rate of 2.25 kg m−2 h−1 under 1 sun irradiance (1 kW m−2) using a 15 wt% NaCl solution, as well as excellent long-term stability for the high-salinity desalination process. The nano-sized channels offer efficient nanoscale light trapping through multiple reflections and scatterations that occur within the channel walls. Furthermore, the abundance of raw materials provides a desirable and efficient approach for converting farm waste to energy, making it particularly well-suited for developing regions.

High-performance multiblock PEMs containing a highly acidic fluorinated-hydrophilic domain for water electrolysis

The present paper describes the design and evaluation of novel hydrophilic–hydrophobic poly(arylene ether sulfone) (PAES) multiblock copolymers for their synergistic effects upon transport properties and their potential use in proton exchange membrane water electrolysis. The multiblock copolymers are prepared via a coupling reaction between (i) a hydrophilic segment consisting of a disulfonated quinone fluorinated biphenyl group that contains fluorine moieties next to the sulfonated groups to increase the acidity, and (ii) hydrophobic segments composed of non-sulfonated biphenyl sulfone to provide dimensional stability. Two different lengths (molecular weights; 5 k and 10 k, where k represents 103 g mol-1) of hydrophobic segments are used to investigate the effects of the membrane properties compared with those of Nafion® and PAES random copolymer (i.e., BPSH40). Atomic force microscopy images of the BPSH40 and multiblock membranes are shown to agree closely with a mesoscale simulation, thus confirming the importance of the morphological effect upon the transport properties. Moreover, the multiblock copolymer with a higher proportion of hydrophilic segments (10 k–5k) was shown to provide enhanced performance (3.41 A cm-2 at 1.9 V) compared to the multiblock copolymer with equal proportions of hydrophilic and hydrophobic segments (10 k–10 k) due to the greater continuity of nano-sized ionic channels.

Nanofluidics for Gas Separation Applications: The Molecular Dynamics Simulation Perspective

ABSTRACT Since past decades, membrane science and technology have received great attention in academia and practice because of their potential for industrial applications. A diverse range of industrial applications has been benefited from this technology thanks to the advances in membrane science. Membranes are of paramount importance in chemical technology and play a key role in a broad range of applications.Membranes incorporating nanosize pores or channels have a tremendous contribution to membrane science discipline, particularly in gas separation technologies. Performing pore-level modeling with the help of computer simulation opens a route to membrane characterization in high accuracy and less observational. By utilizing molecular dynamics simulations, one can provide a fundamental understanding of the static and dynamic features of membranes at a molecular scale. In this work, we have reviewed the recent advances in nanofluidics for gas separation applications, with a major focus on the theoretical literature discussing the gas molecular transport mechanisms through the carbon-based nanopores. Describing the nanofluidics systems, solid-state nanopores, fabrication of nanofluidic devices, pore generation on graphene nanosheets, and pore-level flow modeling, this article expects to provide a platform for understanding the permeation and separation of gases across a variety of nanopores and attracting more attention of audiences from industry and academia.

Covalent organic frameworks with immobilized anions to liberate lithium ions: Quasi-solid electrolytes with enhanced rate capabilities

Ionic liquids (ILs) are promising candidates as fast Li+ conductors owing to their high ionic conductivity and admirable stability. However, the mobile ions in ILs will contribute to the overall ion conductivity which decreases Li ions transfer efficiency and rate capability of batteries. The improvemnt of Li ions transfer efficiency in ILs electrolyte materials is a great challenge. Covalent organic frameworks (COFs) with high porosity and aligned nanosize channels can offer free flowing pathways for Li+ migration as well as abundant active sites to anchor anions and liberate free Li+, which can maximize Li+ transfer efficiency. Herein we design a cationic COF and a neutral COF as porous hosts for immobilizing the anions of IL N,N-diethyl-N-(2-methoxyethyl)-N-methylammoniumbis(trifluoromethylsulphonyl)imide (DEME-TFSI) to enhance Li+ transference efficiency. The obtained quasi-solid COFs-IL electrolytes exhibit high IL loading amount owing to strong interactions between COFs and the IL. Moreover, COFs-IL electrolytes show good electrochemical stability and high ionic conductivity over 1×10−3 S cm−1, along with a 90% increase of Li+ transfer number in comparison to the bare IL electrolyte (IL/LiTFSI). Our research provides a general strategy for immobilizing mobile anions to liberate Li+ and improve Li+ transfer efficiency in IL-based electrolytes.

Single-step equipment-free extracellular vesicle concentration using super absorbent polymer beads.

Extracellular vesicles (EVs) contain useful biomarkers for disease diagnosis and are promising biomaterials for the delivery of therapeutic molecules in vivo. Accordingly, an efficient concentration method is necessary for large‐scale production or high‐throughput isolation of EVs from bulk liquid samples, including culture medium and body fluids, to achieve their clinical application. However, current EV concentration methods, including ultrafiltration, are limited with respect to cost, efficiency, and centrifugation time. In this study, we developed the first single‐step, equipment‐free EV concentration method using super absorbent polymer (SAP) beads. SAP beads absorb small molecules, including water, via nano‐sized channels but expel and thereby concentrate EVs. Consequently, the beads drastically enrich EVs by reducing the solution volume in a single step, without affecting EV characteristics. Moreover, the purity of the concentrated EV solution was high due to the absorption of protein impurities by SAP beads. To further demonstrate the versatility of the method, we showed that SAP beads successfully enrich EVs in human urine samples and culture medium, enabling better isolation performance than conventional ultrafiltration. We believe the newly developed approach and insight gained in this study will facilitate the use of EVs as prominent biomaterials for disease diagnosis and therapy.

Recent Advances in the Application of Metal–Organic Frameworks for Polymerization and Oligomerization Reactions

Polymers have become one of the major types of materials that are essential in our daily life. The controlled synthesis of value-added polymers with unique mechanical and chemical properties have attracted broad research interest. Metal–organic framework (MOF) is a class of porous material with immense structural diversity which offers unique advantages for catalyzing polymerization and oligomerization reactions including the uniformity of the catalytic active site, and the templating effect of the nano-sized channels. We summarized in this review the important recent progress in the field of MOF-catalyzed and MOF-templated polymerizations, to reveal the chemical principle and structural aspects of these systems and hope to inspire the future design of novel polymerization systems with improved activity and specificity.

Nanoporous Gold-Based Sensing

In recent years, the field of nanoporous metals has undergone accelerated developments as these materials possess high specific surface areas, well-defined pore sizes, functional sites, and a wide range of functional properties. Nanoporous gold (NPG) is, surely, the most attractive system in the class of nanoporous metals: it combines several desired characteristics as occurrence of surface plasmon resonances, enormous surface area, electrochemical activity, biocompatibility, in addition to feasibility in preparation. All these properties concur in the exploitatiton of NPG as an efficient and versatile sensong platform. In this regard, NPG-based sensors have shown exceptional sensitivity and selectivity to a wide range of analytes ranging from molecules to biomolecules (and until the single molecule detection) and the enormous surface/volume ratio was shown to be crucial in determining these performances. Thanks to these characteristics, NPG-based sensors are finding applications in medical, biological, and safety fields so as in medical diagnostics and monitoring processes. So, a rapidly growing literature is currently investigating the properties of NPG systems toward the detection of a multitude of classes of analytes highlighting strengths and limits. Due to the extension, complexity, and importance of this research field, in the present review we attempt, starting from the discussion of specific cases, to focus our attention on the basic properties of NPG in connection to the main sensing applications, i.e., surface enhanced Raman spectroscopy-based and electrochemical-based sensing. Owing to the nano-sized pore channels and Au ligaments, which are much smaller than the wavelength of visible light (400–700 nm), surface plasmon resonances of NPG can be effectively excited by visible light and presents unique features compared with other nanostructured metals, such as nanoparticles, nanorods, and nanowires. This characteristics leads to optical sensors exploiting NPG through unique surface plasmon resonance properties that can be monitored by UV-Vis, Raman, or fluorescence spectroscopy. On the other hand, the catalytic properties of NPG are exploited electrochemical sensors are on the electrical signal produced by a specific analyte adsorbed of the NPG surface. In this regard, the enourmous NPG surface area is crucial in determining the sensitivity enhancement. Due to the extension, complexity, and importance of the NPG-based sensing field, in the present review we attempt, starting from the discussion of specific cases, to focus our attention on the basic properties of NPG in connection to the main sensing applications, i.e., surface enhanced Raman spectroscopy-based and electrochemical-based sensing. Starting from the discussion of the basic morphological/structural characteristics of NPG as obtained during the fabrication step and post-fabrication processes, the review aims to a comprehensive schematization of the main classes of sensing applications highlighting the basic involved physico-chemical properties and mechanisms. In each discussed specific example, the main involved parameters and processes governing the sensing mechanism are elucidated. In this way, the review aims at establishing a general framework connecting the processes parameters to the characteristics (pore size, etc.) of the NPG. Some examples are discussed concerning surface plasmon enhanced Uv-Vis, Raman, fluorescence spectroscopy in order to realize efficient NPG-based optical sesnors: in this regard, the underlaying connections between NPG structural/morphological properties and the optical response and, hence, the optical-based sensing performances are described and analyzed. Some other examples are discussed concerning the exploitation of the electrochemical characteristics of NPG for ultra-high sensitivity detection of analytes: in this regard, the key parameters determing the NPG activity and selectivity selectivity toward a variety of reactants are discussed, as high surface-to-volume ratio and the low coordination of surface atoms. In addition to the use of standard NPG films and leafs as sensing platforms, also the role of hybrid NPG-based nanocomposites and of nanoporous Au nanostructures is discussed due to the additional increase of the electrocatalytic acticvity and of exposed surface area resulting in the possible further sensitivity increase.