Nanopore Size Research Articles

Microstructure and strength of microporous MgO refractory aggregates with nano-sized pores

ABSTRACT In this work, microporous MgO refractory aggregates with nano-sized pores were prepared by in situ decomposition method using Mg(OH)2 as raw material. The effects of firing temperatures (1600–1700°C) and compacting pressures (100–200 MPa) on the microstructures and properties of microporous MgO refractory aggregates were thoroughly studied. The results showed that the microporous MgO refractory aggregates contained two types of pore structures, which were intra-particle pores with pore sizes of 180.0–230.0 nm formed by in situ decomposition of Mg(OH)2 and inter-particle pores with pore sizes of 1.5–3.0 μm derived from particle packing between Mg(OH)2 pseudomorph particles, respectively. Besides, the firing temperatures had a great influence on the intra-particle pore size and microcrystallite size. And the compacting pressures not only influenced the intra-particle pore size via packing behaviors but also affected the inner firing behaviors of the pseudomorph particles due to the increase in H2O vapor pressure. Overall, at a compacting pressure of 150 MPa and firing temperature of 1650°C, the sample had the best comprehensive performance with a bulk density of 1.92 g/cm3, a compressive strength of 11.9 MPa, an apparent porosity of 45.0%, a relative aggregate tube strength of 25.2% and a median pore size of 262.3 nm.

A review on the properties of recycled aggregate concrete (RAC) modified with nano-silica

The present study reviews the properties of recycled aggregate concrete (RAC) modified with nano-silica (nS). It has been observed in previous studies that the RAC possesses weaker mechanical properties as compared to natural aggregate concrete (NAC). There are many interfacial transition zones (ITZs) present in RAC. Several attempts have been made in the past to use some mineral additives in the RAC to enhance its mechanical performance. The use of nS is one such choice in this regard. nS possesses high filling ability due to its very small size. It can fill the micro and nano-sized pores and cracks present in RAC. It also improves the weak ITZs. It also has high pozzolanic activity. It reacts with the calcium hydroxide formed during the cement hydration and, in turn, produces additional calcium silicate hydrate (CSH) gel. This additional CSH gel densifies the microstructure of RAC. It is found that the synergistic effect of the two factors, that is, high filling ability and high pozzolanic activity of nS improves the internal structure of the RAC and is responsible for the enhancement of RAC’s properties. It has been observed that the incorporation of nS into the RAC results in a concrete whose strength is comparable to the strength of NAC.

Near-perfect suppression of Li dendrite growth by novel porous hollow carbon fibers embedded with ZnO nanoparticles as stable and efficient anode for Li metal batteries

For the practical application of next-generation Li metal batteries (LMBs), a Li metal anode with high safety and efficiency is essential. However, LMBs still suffer from the problems caused by the growth of Li dendrites at the Li metal anode. In this study, we introduce a novel way that could dramatically suppress the growth of Li dendrites and improve the performance of LMBs. A free-standing porous hollow carbon nanofiber embedded with lithiophilic ZnO nanoparticles (P-HCNF@ZnO) is fabricated using a dual-nozzle electrospinning technique followed by carbonization. The nano-sized pores formed in the shell of hollow carbon fiber provide passages for Li ions to penetrate into the core space of the hollow fiber, and the lithiophilic ZnO particles play a decisive role in inducing and plating Li ions inside the core efficiently and uniformly. Therefore, Li ions are mostly electroplated/stripped on the internal surface of the porous hollow fibers and dendrites are rarely formed on their exterior surface even under fast lithiation conditions, while numerous Li dendrites are formed on the exterior surface of the non-porous hollow fiber electrode (HCNF@ZnO). As a result, the P-HCNF@ZnO electrode exhibits a very low over-potential of about 87 mV, a stable capacity retention of about 95% at a high current density of 1.0 mA cm−2, and a much higher performance than HCNF@ZnO in a symmetric cell test. Furthermore, in full cell tests, the LiFePO4 (LFP) battery made of lithiated P-HCNF@ZnO anode exhibits a high capacity of 175.3 mAh g−1 and a lower over-potential by 0.29 V than the reference sample. Analytical works and theoretical interpretations, elucidated that the Li metal anode made of the P-HCNF@ZnO significantly improves the performance of LMBs.

Hydrothermal synthesis of cobalt substitute zinc-ferrite (Co1-xZnxFe2O4) nanodot, functionalised by polyaniline with enhanced photocatalytic activity under visible light irradiation

Fabrication and development of effective visible-light-responsive photocatalysts are required to tackle critical environmental issues. The aim of this study was to develop a nanocomposite material with improved photocatalytic activity for the degradation of industrial dyes such as Reactive Orange-16 (RO-16), Reactive Blue (RB-222), Reactive Yellow-145 (RY-145), and Disperse Red-1 (DR-1) without the need for a post-separation process after use. Here we report the hydrothermal synthesis of nanodots of Co1-xZnxFe2O4 (x = 0.3, 0.5 and 0.7), coated with polyaniline, by in situ polymerization. The Co1-xZnxFe2O4 nanodots, coated with polyaniline (PANI) nanograins, facilitated optical properties by easily capturing visible light. X-ray Diffraction (XRD) patterns and Scanning Electron Microscopy (SEM) images have confirmed the single-phase spinel structure of Co1-xZnxFe2O4 nanodot and nano-pore size of the Co1-xZnxFe2O4/PANI nanophotocatalyst. The specific surface area of the Brunauer–Emmett–Teller (BET) of the Co1-xZnxFe2O4/PANI photocatalyst was determined to be 24.50 m2/g by multipoint analysis. The final Co1-xZnxFe2O4/PANI (x = 0.5) nanophotocatalyst showed high efficiency in the catalytic degradation of toxic dyes (∼98% within 5 min), with good mechanical stability and recyclability under visible light irradiation. The nanophotocatalyst was re-used and its efficiency was largely maintained, even after seven cycles (∼82%) of degradation. The effects of various parameters, such as initial dye concentration, nanophotocatalyst concentration, initial pH of dye solution, and reaction kinetics were studied. According to the Pseudo-first-order kinetic model, photodegradation data followed the first-order reaction rate (R2 > 0.95) of degradation of dyes. In conclusion, a simple and low-cost synthesis process, speedy degradation and excellent stability of polyaniline-coated Co1-xZnxFe2O4 nanophotocatalyst could be used as a promising photocatalyst for dye-wastewater treatment.

Microstructural characterization and thermal stability of He charged amorphous silicon films prepared by magnetron sputtering in helium

Sputtering of silicon in a Helium magnetron discharge has been reported as a bottom-up procedure to obtain amorphous Si films containing high amounts of gas-filled nanopores. Here we compare the microstructure and composition of Si–He nanocomposite films deposited by magnetron sputtering (MS) with 4He in DC or RF and 3He in RF operation modes. Electron microscopy (SEM and TEM), X-ray diffraction (XRD) and ion beam analysis (IBA) have been used to analyze the films and to investigate the in-situ and ex-situ thermal evolution. Depending on deposition conditions different in depth compositions, nanopore size and shape distributions, porosity and He content could be obtained. The presence of impurities (i.e. oxygen) has shown to promote He diffusivity reducing He accumulation. The start temperature of He-release varied in the range 473–723 K without films crystallization. Films grown in RF mode reached contents of 32 and 29 at% of 4He and 3He and were respectively stable up to 573 and 723 K both in vacuum and under inert gas flow. In-situ p-EBS (proton Elastic Back Scattering) allowed monitoring the He release accompanied by blistering/delamination effects visualized by SEM. These results show the potentiality of annealing to hold nano-porous structures after liberation of trapped gas.

Molecular dynamics simulation study on the hydrophobic mechanism of ettringite nanoporous channels modified by silane and silane/graphene oxide

Sulfoaluminate cement, as an important repairing material in engineering, plays an irreplaceable role in the urgent repair of important engineering facilities. Under the coastal environment, the waterproof demand for concrete is urgent. Silane series coatings are widely used in the waterproofing of concrete. In this paper, the MD method is used to study the multiple interface interaction in the ettringite nanopore, the Isobutyltriethoxy silane(IBTS) and IBTS/graphene oxide(GO with oxidation degree of 5%,10%, and 20%) modified ettringite nanopore under the water erosion. The bonding mechanism of IBTS, GO and ettringite interface and the hydrophobic mechanism of the coatings are analyzed. The hydrophobic efficiency of coatings is IBTS/GO10%≥IBTS/GO20%>IBTS/GO5%>IBTS > Ettringite. IBTS and GO interact with ettringite by hydrogen bonds and Ca-O ionic pairs. The interaction between GO and ettringite substrate is more stable due to its functional groups and larger specific surface area. During water transmission, the IBTS/ettringite interface interaction failed, IBTS desorbed and resulting in coating failure. But GO with a higher oxidation degree can capture the desorbed IBTS to form GO-IBTS hydrophobic network and further reduce the nanopore size and significantly hinder water invasion. This study provides a nano-perspective for the application of IBTS, IBTS/GO coatings in cement-based repair materials.

Hydration states of europium(III) adsorbed on silicas with nano-sized pores

The confinement in small spaces influences the complicated reaction involving water molecules under electrostatic potentials at the solid–liquid interface. It is unclear, in particular, how the hydration state of metal ions adsorbed on the surface changes as a function of the pore size. This study analyzed the adsorption states of europium aqua ions (Eu3+) on mesoporous silicas with different pore distributions in comparison with nonporous silica using time-resolved laser-induced fluorescence spectroscopy. The parallel factor analysis was used to differentiate the contribution of different chemical species of Eu3+ to the fluorescence signal and determine the influence of the pore size on each chemical species. The results show that Eu3+ mainly form outer-sphere complexes with silica below pH 6, where Eu3+ adsorption is low. Within nano-sized pores, distortion of the hydration structure and a decrease in the hydration number were suggested in this pH range. As the concentration of the silicate ions derived from the dissolution of silica increases with increasing pH, Eu3+ form the silica/Eu3+/silicate ternary surface complexes. Within nano-sized pores, the concentration of silicate ions decreases due to the overlap of the electric double layer, which inhibits the formation of the ternary surface complex. Furthermore, at high pH, Eu3+ multinuclear complexes formed only on the mesoporous silica surface. This adsorption behavior specific to nano-sized pores could not be concluded by macroscopic adsorption experiments alone because the amount of Eu3+ adsorbed per unit surface area did not differ between the mesoporous and nonporous silicas. Consideration of the silicate complexes should be indispensable in future studies on the adsorption of lanthanide ions using mesoporous silica.

Sodium Diffusion in Hard Carbon Studied by Small- and Wide-Angle Neutron Scattering and Muon Spin Relaxation

Hard carbon is the most common anode material for Na-ion battery. The structure of the hard carbon and the dynamics of Na-ion in hard carbon were studied with small- and wide-angle neutron scattering and muon spin relaxation technique. The neutron scattering revealed the increase of interlayer distance between graphenes and decrease of the size of nanopores with increasing sodium intercalation in hard carbon. The muon spin relaxation revealed that a systematic increase in the field fluctuation rate with increasing temperature evidenced a thermally activated sodium diffusion. Assuming the two-dimensional diffusion of Na-ion in the graphene layers, the self-diffusion coefficient of Na-ion was estimated to be 2.6 × 10−11 cm2/s at 310 K, with a thermal activation energy of 39(7) meV.

Graphene-based magnetic composite foam with hierarchically porous structure for efficient microwave absorption

In the design of microwave absorbing materials, synergistically optimizing the relationship between impedance matching and attenuation constant remains a great challenge. In this work, a hierarchically porous graphene/iron trioxide magnetic composite foam (GMF) is successfully constructed by an electrostatic assembly of metal-organic frameworks (MOF) in reduced graphene oxide skeletons and subsequent annealing treatment. As a unique template, the in-situ pyrolysis of MOF facilitates the transition from flake-like MOF to anisotropic porous magnetic nanosheet (Fe2O3), promoting the composites to break Snoek's limitation. The combination between magnetic nanosheets and conductive graphene skeletons can further optimize the impedance gradient and attenuation constant of those foams. More importantly, the successful construction of hierarchically porous magnetic foam from micro-to nano-sized pores effectively induces the generation of huge multiple scattering and defect polarization. As a result, more incident electromagnetic waves thus are allowed to enter the materials and dissipate as much as possible after entering the foam, endowing the composite foam with an excellent absorption capacity (−60.13 dB) and bandwidth (6.23 GHz).

Effect of inter-pore interference on liquid evaporation rates from nanopores by direct simulation Monte Carlo

Liquid evaporation from micro/nanoscale pores is widely encountered in cutting-edge technologies and applications. Due to its two- or three-dimensional features, the nano-porous evaporation is less understood compared to the one-dimensional evaporation of a planar liquid surface. This paper reported a novel study of the inter-pore interference effect in nano-porous evaporation, clarifying the variation in the net evaporation rate from individual nanopores when the inter-pore distance, neighboring nanopore diameter, or liquid temperature were changed. Molecular simulation results showed that the reduction in inter-pore distance could enhance the evaporation rate from nanopores by augmenting the vapor convection effect and suppressing the condensation flux. This interference effect was more pronounced at lower evaporation intensity with the evaporation flux being different by up to 25% from the one-dimensional case. The inter-pore interference was equally observed for Knudsen numbers of 0.1 and 10. Additionally, the non-uniformity in nanopore size distribution had no influence on the evaporative mass flux within the present parameter range. The non-uniformity in nanopore temperatures, however, could affect the net evaporation from individual nanopores, similarly by modulating the vapor convection magnitude in adjacent to the interface and the condensation flux. The effect of inter-pore interference is found to be essential at low evaporation intensity, which is highly relevant in industrial applications such as water evaporation under atmospheric pressure.

Ethane groups modified DNA nanopores to prolong the dwell time on live cell membranes for transmembrane transport.

Transmembrane transport, mostly relying on biological channels, is crucial for the metabolic processes of live cells including sensing, signaling, cellular communicating and molecular transport. Artificial biomimetic channels offer excellent opportunities for studying the mechanisms of the metabolic processes of live cells and promote the applications of gene transfection, drug delivery, and regulations of cellular communications. DNA nanopores can be designed flexibly and operated easily while maintaining good biocompatibility, offering a good candidate for applications in basic research. However, because of the small size and good biocompatibility of DNA nanopores, it is still difficult to form stable channels on the plasma membrane of live cells by DNA nanopores. As a result, it significantly limits the applications of DNA nanopores in vivo. Thus, in this work, we have constructed ethane-phosphorothioate (PPT) groups modified DNA nanopores (E-DNA nanopores) to simulate biological channels for the transmembrane transport of small molecules. The E-DNA nanopores were found to be more hydrophobic and stable to anchor at the plasma membrane of live cells for a longer time window for subsequent transmembrane transport after the modification of ethane-PPT groups. The membrane-spanning E-DNA nanopores with a longer dwell time window could inspire the design of new DNA nanostructures and expand their biological applications including biosensing and sequencing, construction of artificial cells and regulation of transmembrane transport.

Co-Optimizing Insulative and Mechanical Properties of Quartz Fabric Reinforced Phenolic Composites by a Compromising Porous Structure for Thermal Insulation

Introducing porosity into structures is recognized as a practical strategy to achieve lightweightness and insulation for ablatives, but reduced matrix density leads to the weakening of mechanical and anti-ablation performances. Herein, a trade-off design of the porous structure is developed for integrating high-strength, insulation, and anti-ablation abilities into mid-density nanoporous phenolic composites (NPC). Benefiting from a narrow nanopore size (20–62 nm) of the matrix, thermal conductivity of NPC can be effectively limited within 0.079–0.115 W/(m·K), while showing a mid-density of 0.89–1.04 g/cm3. Meanwhile, NPC shows a considerable axial tensile strength of 130.2–177.8 MPa and out-of-plane compressive strength of ∼300 MPa due to the compromising porosity (34–62%) and reinforcing of the 3D needle-punched quartz fiber preform. Besides, NPC exhibits excellent oxidation resistance in static radiation heating (1000 °C) and outstanding insulation and ablation resistance under an oxy-acetylene heat flux of 1.76 and 4.18 MW/m2 with the linear ablation rates of ∼0.102 and ∼0.185 mm/s, respectively. The results will further promote the development and application of phenolic ablatives in extreme re-entry environments.

Response of Bilayer and Trilayer Graphene to High-Energy Heavy Ion Irradiation

High-energy heavy ion irradiation is a very useful tool for the nanostructuring of 2D materials because defects can be introduced in a controlled way. This approach is especially attractive for the mass production of graphene nanomembranes when nanopore size and density can easily be tuned by ion irradiation parameters such as ion energy and applied fluence. Therefore, understanding the basic mechanisms in nanopore formation due to high-energy heavy ion impact is of the highest importance. In the present work, we used Raman spectroscopy to investigate the response of bilayer and trilayer graphene to this type of irradiation. Spectra obtained from graphene samples irradiated with 1.8 MeV I, 23 MeV I, 3 MeV Cu, 18 MeV Cu, and 12 MeV Si beams were analysed using the Lucchese model. It was found that the efficiency of damage production scales strongly with nuclear energy loss. Therefore, even for the most energetic 23 MeV I beam, the electronic energy loss does not contribute much to damage formation and ion tracks are unlikely to be formed.

Electrical detection and analysis of exosomes by a glass capillary nanopore.

An exosome is a vesicle less than 200 nm in diameter released from a cell and works as a medium for cell-to-cell communication. It is suggested that compositions of encapsulated molecules in exosomes have diversity even from a same cell. Single-particle analysis will be insight into the understanding the diversity, but it is still challenging. Nanopore technology will have a potential to detect and to capture single exosomes because it can discriminate nanoparticle properties including size, shape, and surface properties such as the charge by observation of ionic current change through a nano-sized pore. Here, we proposed to use a glass capillary nanopore (φ∼200 nm) and attempt to capture milk exosomes. Exosomes used in this study were extracted from cow milk using a procedure proposed previously. The particle sizes were confirmed by dynamic light scattering (DLS). A glass capillary nanopore was prepared by a puller. We observed the pore diameter of the capillaries by a scanning electron microscope (SEM). In the nanopore experiments, a glass capillary was filled with and immersed in PBS solution to measure I-V curve for checking the pore conductance, and then it was replaced in the exosome solution to detect the exosomes. The size of extracted exosomes was confirmed by DLS, and it was consistent with that in a previous study (∼130 nm). The outer diameter of the glass nanopores ranged from about 100 to 500 nm determined by SEM observation. For channel current measurement, the current blockages were observed in the presence of exosomes that was depended on the polarity of the applying voltages. We are conducting identification of microRNA encapsulated in exosomes collected from the nanopore by RT-qPCR, and it will be discussed in San Diego.

Experimental investigation of the forces dictating polymer translocation through solid-state nanopores.

After realizing direct long-read DNA and RNA sequencing, nanopores show also potential for decoding information on other polymers, including proteins and nanostructured DNA. Understanding the process by which these biopolymers are captured and traverse nanopores however remains a challenging task due to the complex nature of the non-equilibrium translocation dynamics which occur on multiple timescales and are dictated mainly by forces over which full experimental control is challenging. This unfortunately also makes verification of theoretical ideas difficult. In this work, we present solid-state nanopore data of DNA fragments for a wide range of experimental conditions in hopes of showcasing the various underlying forces and processes during capture and translocation. Namely, we specifically attempt to establish the absolute and relative magnitude of electrophoretic forces, and frictional contributions originating from hydrodynamic interactions both inside and outside nanopores. This is achieved by studying the dependence of translocation times on nanopore size (3-20 nm diameter) and DNA length (500-45,000 bp), and by measuring the time-dependent translocation velocity of DNA nanostructures, which consists of a linear DNA polymer with three helix-bundle (3HB) sub-structures patterned along its contour. The velocity profile of the patterned nanostructure is measured under different applied voltages (0.1-1 V), in different salt concentrations (0.5-4 M LiCl), and in different pore geometry. The data allow us to corroborate the predictions of tension propagation and consolidate previously published observations regarding measurements of electrophoretic pulling force and pore-polymer interactions in nanopore systems. In addition to bridging nanopore experiment and theory, these results can be used to inform and design several biosensing and digital storage applications.

Electrophoretic motion of hydrophobic spherical particles in nanopore: Characteristics, separation, and resistive pulse sensing

Electrophoretic motion of hydrophobic particles has been scrutinized numerically in solid-state nanopores. The Poisson, Stokes, and Nernst–Planck equations are solved simultaneously, and the Newton–Raphson algorithm is used to compute the correct velocity at each point. For the hydrophobic surface characterization, the Navier-slip boundary condition with a wide range of slip lengths is applied to the nanoparticle's surface. The effects of the electric field intensity, the electrolyte concentration, and the particle's size on the electrophoretic velocity are examined. Then, the nanopore's size and surface charge density are manipulated to achieve the configuration for separating hydrophobic and hydrophilic particles based on their slip lengths. The results show that the hydrophobic and hydrophilic particles, under particular circumstances, would move in the opposite direction in a nanopore. Finally, the resistive pulses of the particles with various slip lengths are studied. The resistive pulse properties of the hydrophobic and the hydrophilic particles are completely distinguishable and show potential application for resistive pulse sensing as a tool for reckoning the particle's slip length.

De novo design of β-barrel nanopore with Gly-kink towards single-molecule detection.

Nanopore sensing is a rapid and label-free method for single-molecule detection of DNA, peptides, and protein. However, it remains challenging to adjust the size and geometry of nanopores for each target molecule using biological nanopores. Therefore, constructing size and geometry controllable nanopore is highly demanded. Recently, de novo design has enabled the creation of specific structures and functions of proteins. We have previously designed a de novo β-hairpin peptide named SV28, which is assembled to form a multidisperse-sized β-barrel nanopore in a bilayer lipid membrane (BLM). A monodisperse-size nanopore is required for the highly sensitive detection of a specific target. Toward constructing a monodisperse-sized nanopore, we focused on Gly-kink. In the computational protein design, introducing the Gly-kink in a β-barrel structure makes the packing of the β-strands relaxed and the β-barrel structure to be more rigid. Then, we redesigned SVG28 with the introduction of Gly-kink into SV28. To evaluate the pore-forming ability of SVG28, we conducted channel current measurement with BLM in microdevices and signal classification analysis. As result, the SVG28 nanopore converged relatively monodisperse size (SVG28: φ = 1.7 nm, SV28: φ = 1.7-6.3 nm). Moreover, we carried out molecular dynamics simulations of peptide nanopores, indicating the stabilization of the β-barrel structure by introducing the Gly-kink. For future nanopore amino acid sequencing, we applied SVG28 nanopore to polypeptide detection. The SVG28 nanopore could detect and discriminate molecular weight difference of poly-l-lysine (PLL: φ = 1.1-1.4 nm). Furthermore, the SVG28 nanopore could identify the single amino acid in the oligo-arginine with several different types of single amino acids (R7X: φ = 1.0-1.5 nm). The above achievements are due to size and geometry matching between the SVG28 nanopore and the targets. Now, we are redesigning SVG28 to construct nanopores that have specific large pore sizes for protein detection.

Experimental study of the mechanism of nanofluid in enhancing the oil recovery in low permeability reservoirs using microfluidics

Due to the low porosity and low permeability in unconventional reservoirs, a large amount of crude oil is trapped in micro-to nano-sized pores and throats, which leads to low oil recovery. Nanofluids have great potential to enhance oil recovery (EOR) in low permeability reservoirs. In this work, the regulating ability of a nanofluid at the oil/water/solid three-phase interface was explored. The results indicated that the nanofluid reduced the oil/water interfacial tension by two orders of magnitude, and the expansion modulus of oil/water interface was increased by 77% at equilibrium. In addition, the solid surface roughness was reduced by 50%, and the three-phase contact angle dropped from 135° (oil-wet) to 48° (water-wet). Combining the displacement experiments using a 2.5D reservoir micromodel and a micro-channel model, the remaining oil mobilization and migration processes in micro-to nano-scale pores and throats were visualized. It was found that the nanofluid dispersed the remaining oil into small oil droplets and displaced them via multiple mechanisms in porous media. Moreover, the high strength interface film formed by the nanofluid inhibited the coalescence of oil droplets and improved the flowing ability. These results help to understand the EOR mechanisms of nanofluids in low permeability reservoirs from a visual perspective.

Nanobubble-governed membrane with nanofluidic channels for efficient molecule/ion sieving

Nanobubbles play key roles in determining various interfacial properties. However, investigation of water/ions transport behavior in nanobubble-governed nanofluidic channel was limited by the resolution of current in-situ observation techniques. Here, we investigated selective nanofluidic transport in nanobubble-plugged nanochannel during cross-flow forward osmosis (FO) process with a combined approach of simulations and experiments. Nanobubbles were generated by mechanical vibration during FO process. A nanobubble-plugged nanochannel model established via finite element modeling was used to explore nanobubble-governed selective water/ions transport. FO experimental results also verified nanobubble-plugged nanochannels with different asymmetric wettability and nanopore sizes could achieve unidirectional water transport while near-zero salt diffusion. Ion sieving tests further demonstrated nanobubble-plugged nanochannel could impede salt ions by nanobubble gating with size sieving, hydrophobic interaction and electrostatic interaction between nanobubbles and salt ions. These findings have implications for understanding selective nanofluidic transport in nanobubble-governed nanofluidic channel, which also provide new routes for designing potential osmosis membranes for high performance desalination.

Thermal and acoustic insulation properties in nanoporous geopolymer nanocomposite

In building and construction sector, seeking for high thermal and sound insulation materials is crucial to reach lower carbon footprints and also for curtailed consumption energy either for heating or for cooling. Nowadays, geopolymer nanocomposites, an alternative binder to Ordinary Portland Cement (OPC), are drawing considerable attention for their great prospective to withstand heat and sound exposure beside to their outstanding properties including high early strength, little creep and shrinkage and a good resistance to corrosion and abrasion. To advance geopolymer insulating properties, a nanoscale analysis has been investigated here to consider porosity, nanopore size, moisture as well as chemical composition and alkali agents impacts. Our findings conclude that a better thermal isolation is predicted for a high-silicon content geopolymer nanostructure with the presence of sodium alkali activators. The lowest thermal conductivity values of 0.08 W/m.K and 0.10 W/m.K are obtained for a porosity of 30.8% for Na+ and K+ samples, respectively. Considering humidity, results indicate that residual water enhances 4.5 times the thermal insulation of a highly nanoporous metakaolin geopolymer rich on silicon and in the presence of NaOH alkali activator. Nanoscale investigation has finally shown a promising acoustic insulation behavior than OPC material when pore size and porosity are higher than 12 Å and 20% respectively, making nanoporous geopolymer paste as a great challenge for cementitious materials.