Nanopore Size Research Articles

Research on high-quality factor sensing characteristics of all-dielectric nanopore array metasurface based on POA-DELM

Abstract Based on the optical properties of symmetric structures independent of each other in the orthogonal direction, an all-dielectric nano-square hole array metasurface which is symmetric along the diagonal is proposed. By changing the size of square nanopores, the symmetry of the periodic unit structure is broken and the double Fano resonance can be excited. The influence of each structural parameter on the sensing performance of the metasurface is analyzed respectively. As the main structural parameters and performance index, the metasurface height and the lengths of the main and sub-diagonal square nanoholes are selected as the input parameters, and the figure of merit (FOM) value is used as the output value. Then the nonlinear mapping relationship between the input and the output is established through deep extreme learning machine (DELM). Different optimization algorithms are used to optimize the weighted FOM values globally. The four evaluation indicators including root mean square error (RMSE), mean absolute error (MAE), mean absolute percentage error (MAPE), and model fit (R-squared, R2) are used to assess the training effectiveness of the model. It is shown that the indexes are 0.9986, 0.9725, 3.1612 and 0.9733 respectively, and the FOM values of the dual Fano resonance after pelican optimization algorithm ( POA ) optimization are as high as 9.88 × 103 and 1.28 × 105, which demonstrate the effectiveness of POA-DELM proposed in this paper.

Nanometer-Scale Tunable mesopores in silica fillers for Facile enhancement of epoxy adhesion

Epoxy resins are essential polymeric materials for various industrial applications owing to their excellent adhesion, thermal properties, and processability. Reported improvement methods for overcoming the limitations of epoxy-resin adhesives involve incorporating fillers such as silica, clay, carbon nanotubes, and graphene. While silica nanoparticles are commonly used in industrial applications, their properties often require enhancement. In this study, mesoporous silica nanoparticles (MSNs) were synthesized using cetyltrimethylammonium bromide and novel swelling agents, 2,6-dihydroxybenzoic acid and decane, to control pore sizes within the 2–4 nm range. Transmission electron microscope and nitrogen adsorption analyses confirmed pore sizes of 2.0, 3.1, and 3.9 nm. Applying MSNs as nanofillers to epoxy resin adhesive resulted in enhanced adhesive properties with increasing pore size, particularly with 0.5 wt% MSN-4 nm, achieving a 51.4 % improvement in shear strength compared to that of bare epoxy resin. This enhancement is attributed to the increased specific surface area of the MSNs, providing more interaction sites with the epoxy resin and improving resin penetration and interaction. These findings highlight the critical role of nanopore size in optimizing adhesion in nanofiller applications and emphasize the potential of MSNs as superior nanofillers for future industrial applications.

Transcriptomic analysis reveals the mechanism underlying salinity-induced morphological changes in Skeletonema subsalsum

Diatom cell walls are diverse and unique, providing the basis for species identification and supporting the ecological and economic value of diatoms. However, these important structures sometimes change in response to environmental fluctuations, especially under salt adaptation. Although studies have shown that salinity induces morphological plasticity changes in diatom cell walls, most research has focused on physiological responses rather than molecular mechanisms. In this study, Skeletonema subsalsum was cultured under four salinity conditions (0, 3, 6, 12). Through morphological and physiological methods, we found that salinity increased the cell diameter, protrusion lengths, distance between adjacent cells (DBCs), and nanopore size, while reducing cell height and silicification degree. To further investigate the mechanism underlying morphological changes in S. subsalsum, complementary transcriptome analysis was performed. In total, 20,138 differentially expressed genes (DEGs) were identified among the four treatments. Among them, 231 DEGs were screened and found to be closely associated with morphological changes, of which 107 were downregulated and 124 were upregulated. The findings demonstrated that elevated salinity inhibited silicon transport and deposition via downregulating the expression of DEGs involved in functions including chitin metabolism, putrescine metabolism, and vesicle transport, resulting in reduced silicon content and cell height. Increased salinity promoted the expression of DEGs related to microtubules (MTs), actin, and ubiquitin, which synchronously induced morphological changes. These findings provide a more comprehensive understanding of the salt tolerance of algae and a foundation for future studies on cell wall morphogenesis.

Controlled Nanopore Sizes in Supraparticle Supports for Enhanced Propane Dehydrogenation with GaPt SCALMS Catalysts

Controlled Nanopore Sizes in Supraparticle Supports for Enhanced Propane Dehydrogenation with GaPt SCALMS Catalysts

A Monte Carlo Study on a 3-Dimensional Comb Polymer Translocation through a Nanopore driven by an Electric Field

Abstract A lattice Monte Carlo simulation study of the translocation of comb polymers through a nanopore subjected to an electric field is presented. The translocation dynamics was extensively studied in terms of the applied electric field strength, the pore size, and the comb polymer topology. The variations of the most probable translocation time $\tau_p$ and the mean translocation time \mt\ as a function of the applied electric field strength show distinct features, the latter exhibiting a nonmonotonic dependence on the electric field. We were able to show the existence of a critical field strength $\delta \epsilon_c$ defined by the narrowest distribution of the translocation time, which is closely related to the size of the nanopore. In addition, we have found that the critical field strength also defines a transition point between two regimes of translocation: a smooth translocation for a field strength below $\delta \epsilon_c$ and a chaotic translocation for a field strength above $\delta \epsilon_c$. Moreover, for the smallest pore size ($r_p = 1$), monomers can only cross the nanopore in a single file, while for larger pores different modes of polymer translocation are identified. Finally, the dependence of the mean translocation time on the backbone length is governed by a power law relationship $\left < \tau \right > \sim {N_B}^{\alpha}$, where the scaling exponent $\alpha$ is found to be in the range of 1.3--1.7 for the set of side chain lengths and nanopore sizes investigated. As for the side chain length $N_S$, the mean translocation time is found to follow a linear dependence $\left < \tau \right > \sim {N_S}$.

Structural and Hydrophilic Properties of Nanoporous Aluminium Oxide Film as a Function of Voltage Anodization

Abstract The impact of voltage on the formation of nanopores through electrochemical anodization of high-purity aluminum was examined. The electrochemical bath was carefully prepared with oxalic acid electrolyte, while a 99.5% pure aluminum electrode served as the cathode and an aluminum template as the anode. The anodization process was conducted at room temperature, with voltage increments ranging from 20V to 65V, which was made possible by the in-house electrochemical cell. Notably, each incremental increase in voltage yielded a significant surge in current density, accompanied by a marked expansion in nanopore size, growing from approximately 35 nm to 125 nm. X-ray diffractometry, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Rutherford backscattering spectrometry were used to characterize the films. A slight phase change was observed in the aluminum substrate's FCC structure after the anodization process, transitioning to a monoclinic structure at 39° and 45° for all applied potentials. The stoichiometry of the films was determined through RBS analysis. The nano pores' resulting morphology and phase composition were further examined using SEM and EDS, providing insights into their structural characteristics. Furthermore, the water contact angle of the anodized aluminum oxide samples was measured, revealing a range of approximately 85.16 to 61.01 degrees.

Response of nano-pores and heterogeneity of tar-rich coal to microwave pyrolysis

ABSTRACT In-situ pyrolysis of tar-rich coal can alleviate the external dependence of oil and gas in China, and achieve efficient and safe exploitation of tar-rich coal. In fact, the nano-pores and heterogeneity of tar-rich coal undergo significant changes during pyrolysis, but there is currently limited research, which seriously restricts the efficient utilization of tar-rich coal. In this study, the pore and heterogeneity characteristics of tar-rich coal were studied by microwave pyrolysis experiment, gas adsorption results and multifractal theory, and the pyrolysis evolution mechanism of pores of tar-rich coal was proposed. The results show that microwave pyrolysis significantly promoted the development of nano-pores in tar-rich coal. The nano-pore size distribution of tar-rich coal after pyrolysis showed obvious multifractal characteristics, and the influence of sparse area on nano-pore size distribution was more obvious, while the nano-pore distribution heterogeneity increases initially and subsequently drops with temperature. Moreover, the development of nano-pores in tar-rich coal occurred in three stages. Stage I, the total pore volume changed little, increasing only from 0.06851 to 0.09463 ml/g, and thermal cracking is the main reason for pore development. Stage II, numerous pores were produced as a result of the pyrolysis products’ generation, and total pore volume grew rapidly increased to 0.331 ml/g. Stage III, liquid hydrocarbons and precipitated volatile products blocked nano-pores, so that the total PV began to decrease. The total pore volume was only 0.19967 ml/g at 1000°C. This study provides guidance for the investigation of pore evolution during pyrolysis and enriches the theory of in-situ pyrolysis of tar-rich coal.

Programmable light‐driven soft actuator enabled by structurally anisotropic liquid crystalline network

AbstractThe design and fabrication of advanced soft actuators with programmable actuation are highly desirable in constructing intelligent soft robots. In this work, a programmable light‐driven liquid crystalline network (LCN)‐based soft actuator was judiciously designed and prepared by constructing structural anisotropy across the thickness of the film. A three‐dimensional (3D) deformable LCN actuator was realized by polymerization‐induced phase separation of small‐molar‐weight monomers and polymer networks. The resultant anisotropic LCN displays anisotropic microscale nanoporous architecture across the thickness in addition to uniform alignment at the molecular scale. The actuation behaviors of LCN film are tunable by adjusting the size and distribution of nanopores in LCN bulk via changing polymerization conditions and monomer components. More importantly, the nanoporous LCN film can be harnessed as a promising template to achieve diverse light responsiveness by changing the photothermal dyes via a feasible washing and refilling process, demonstrating a reprogrammable light‐driven soft actuator.

Polyoxometalate-induced hydrogel with in situ nano/bioenzyme cascade reaction generating intensive and long-lasting glow-type chemiluminescence

In this study, we introduce a straightforward one-step, in-situ strategy for the generation of long-lasting and intensive glow-type chemiluminescence (CL) for glucose sensing in biological samples. The approach involves the utilization of polyoxometalate (POM)-induced alginate hydrogel, which effectively encapsulates both the catalysts (POM and glucose oxidase (GOx)) and the CL reagent (luminol) in solution. Leveraging the peroxidase-like nanozyme properties of POM and the bioenzyme GOx, embedded within the nano-sized pores of the hydrogel, we achieve intensive and persistent CL emission lasting over 16 h. The POM-hydrogel-based CL system demonstrates remarkable storage stability and reproducibility, and it can be applied to quantitatively determine serum glucose with high accuracy. Our study indicates that the POM-hydrogel platform, supporting and confining nano/bioenzyme cascade reactions, holds great promise for the establishment of glow-type CL systems, which could be of great value in various fields of CL biosensing and imaging.

Blobs form during the single-file transport of proteins across nanopores

The transport of biopolymers across nanopores is an important biological process currently under investigation for the rapid analysis of DNA and proteins. While the transport of DNA is generally understood, methods to induce unfolded protein translocation have only recently been discovered (Yu et al., 2023, Sauciuc et al., 2023). Here, we found that during electroosmotically driven translocation of polypeptides, blob-like structures typically form inside nanopores, often obstructing their transport and preventing addressing individual amino acids. This is in contrast with the electrophoretic transport of DNA, where the formation of such structures has not been reported. Comparisons between different nanopore sizes and shapes and modifications by different surface chemistries allowed formulating a mechanism for blob formation. We also show that single-file transport can be achieved by using 1) nanopores that have an entry and an internal diameter smaller than the persistence length of the polymer, 2) nanopores with a nonsticky (i.e., nonaromatic) inner surface, and 3) moderate translocation velocities. These experiments provide a basis for understanding polypeptide transport under confinement and for improving the design and engineering of nanopores for protein analysis.

Size-tunable transmembrane nanopores assembled from decomposable molecular templates

Transmembrane nanopores, as key elements in molecular transport and single-molecule sensors, are assembled naturally from multiple monomers in the presence of lipid bilayers. The nanopore size, especially the precise diameter of the inner space, determines its sensing targets and further biological application. In this paper, we introduce a template molecule-aided assembly strategy for constructing size-tunable transmembrane nanopores. Inspired by the barrel-like structure, similar to many transmembrane proteins, cyclodextrin molecules of different sizes are utilized as templates and modulators to assemble the α-helical barreled peptide of polysaccharide transporters (Wza). The functional nanopores assembled by this strategy possess high biological and chemical activity and can be inserted into lipid bilayers, forming stable single channels for single-molecule sensing. After enzyme digestion, the cyclodextrins on protein nanopores can be degraded, and the remaining nontemplate transmembrane protein nanopores can also preserve the integrity of their structure and function. The template molecule-aided assembly strategy employed a simple and convenient method for fully artificially synthesizing transmembrane protein nanopores; the pore size is completely dependent on the size of the template molecule and controllable, ranging from 1.1 to 1.8 nm. Furthermore, by chemically synthesized peptides and modifications, the pore function is easily modulated and does not involve the cumbersome genetic mutations of other biological techniques.

Hierarchically Micro- and Nanostructured Polymer via Crystallinity Alteration for Sustainable Environmental Cooling.

Cooling environments are a pervasive need in our society, with conventional air conditioners being the most popular approach. However, air conditioners rely heavily on electricity and Freon, a chemical that depletes ozone and contributes to greenhouse gas effects. To address this issue, passive daytime radiative coolers (PDRCs) have been proposed to achieve cooling by simultaneously reflecting sunlight and allowing internal heat to escape without electricity. Despite their potential, most high-performance PDRCs are composed of thick polymer films, which increases material costs during PDRC preparation and limits thermal transport. In this work, we introduced an economical and scalable solvent evaporation-based method to prepare a relatively thin hierarchically micro- and nanostructured poly(vinylidene fluoride-trifluoroethylene) via crystallinity alteration. Particularly, we find that the key to generating nanosized pores is to remove the water residual within the film without sample annealing, which significantly enhances the scattering efficiency across the solar spectrum. With our design, we demonstrate effective cooling of the outdoor environment, achieving a cooling temperature of Δ2.5 °C, with a film thickness of only 215 μm. Furthermore, our model suggested that applying this material could lead to annual energy savings of up to ∼39% in warmer climates across the country and up to 715 GJ nationwide. Developing effective PDRCs with reduced material thickness, such as the one discussed here, is imperative for implementing sustainable cooling solutions and reducing our carbon footprint.

Wetting mechanism and alteration of nano-sized shale pores: Insights from contrast variation small angle neutron scattering

Wettability of tight shale is crucial for fluid flow and mass transport process in energy geosciences. However, understanding the interfacial chemistry and wetting mechanisms at sub-nano-pore scales remains a formidable challenge. In this study, the Contrast Variation technique of Small Angle Neutron Scattering (CV-SANS) is employed to investigate shale’s interfacial chemistry using reagents that possess a range of different polarities, including water, n-decane, toluene, and dimethyl methanamide. Through five different experimental strategies, we have demonstrated a successful modification of shale wettability, ranging from enhancement, weakening, to reversal. Delving into the mechanisms, we illustrated the crucial role of pre-existing liquid films in these changes, where the uniquely co-existing polar and non-polar functional groups in dimethyl methanamide acted as a conduit for interfacial chemistry adjustments. Furthermore, a solvent immersion led to matrix dilation as well as liberation of residual oil-occupied pores, resulting in altered pore size distributions, with hydrogen bonding playing a significant role in the polar groups. Interestingly, despite shale exhibiting a stronger affinity for oil over water, hydrophilic solvents induced more substantial dilation than lipophilic ones. Collectively, this work elucidates the dynamic change of interfacial chemistry via the configuration of polarity using chemical reagents, and the CV-SANS technique underscores its invaluable utilities in decoding the interfacial wettability traits in nanopore space of shale.

Analysis of structural defects and their influence on red-emitting γ-Al2O3:Mn4+,Mg2+ nanowires using positron annihilation spectroscopy.

The present paper reported on the analysis of structural defects and their influence on the red-emitting γ-Al2O3:Mn4+,Mg2+ nanowires using positron annihilation spectroscopy (PAS). The nanowires were synthesized by hydrothermal method and low-temperature post-treatment using glucose as a reducing agent. X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL), and photoluminescence excitation (PLE) were utilized, respectively, for determining the structural phase, morphology and red-emitting intensity in studied samples. Three PAS experiments, namely, positron annihilation lifetime (PAL), Doppler broadening (DB), and electron momentum distribution (EMD), were simultaneously performed to investigate the formations of structural defects in synthesized materials. Obtained results indicated that the doping concentration of 0.06% was optimal for the substitution of Mn4+ and Mg2+ to two Al3+ sites and the formation of oxygen vacancy (VO)-rich vacancy clusters (2VAl + 3VO) and large voids (~0.7 nm) with less Al atoms. Those characteristics reduced the energy transfer between Mn4+ ions, thus consequently enhanced the PL and PLE intensities. Moreover, this optimal doping concentration also effectively controlled the size of nanopores (~2.18 nm); hence, it is expected to maintain the high thermal conductivity of γ-Al2O3 nanowire-phosphor. The present study, therefore, demonstrated a potential application of γ-Al2O3 nanowire-phosphor in fabricating the high-performance optoelectronic devices.

Modeling nanogratings erasure at high repetition rate in commercial optical glasses

Volume nanogratings (NGs) imprinted by infrared femtosecond laser in commercial optical glasses take the form of orientable subwavelength birefringent nanostructures, being composed of an assembly of nanopores. The existence of NGs strongly depends on the laser parameters and glass composition. Therefore, in this work, we tentatively model the erasure threshold of NGs in a pulse energy - repetition rate processing window. For this purpose, we combine i) a heat diffusion model to simulate the thermal treatment experienced by the glass upon laser irradiation, and ii) the Rayleigh-Plesset equation to take into account the evolution of a nanopore size during laser processing. We first determine a criterion for nanopores erasure, falling within a typical characteristic time of few tens of ns, in which the cooling of the last laser pulse absorbed by the material is progressively cooled. Then, considering a multiple pulse regime and the dependence of the deposited pulse numbers on the thermal treatment, the modeled NGs erasure threshold follows the experimental trend. Finally, considering a steady state regime for various repetition rates, and adjusting the energy deposition (absorption coefficient or beam waist) as a function of the pulse energy, the NGs existence window can perfectly match the experimental values.

Electroless Plating of Nanoporous Substrates for Thin Film-Solid Oxide Fuel Cells

Thin-film solid oxide fuel cells (TF-SOFCs) are an attractive renewable energy source due to their high efficiency, increased power output and ability to be efficiently stacked for power generation at a small or large-scale. [N. Q. Minh, J Am Ceram Soc. 1993; 76(3):563-588.] Nanoporous Al2O3, also known as anodized aluminum oxide (AAO) is an appropriate substrate for TF-SOFCs due to its high temperature stability, chemically inert nature, and porosity that allows gas flow to the anode. The aligned, nano-sized pores allow for both conformal sputtering on the surface and efficient fuel delivery to the anode, making it particularly suited for thin film deposition. Electroless nickel plating is used to achieve a fully conductive, nanoporous substrate which catalyzes the hydrogen oxidation reaction and improves current collection efficiency in TF-SOFCs. A minimum plating temperature of 60°C is needed to grow nanoscale Ni deposits into a conductive film without compromising the porosity of the surface. Effective stirring methods are used to deliver the plating solution throughout the high-aspect ratio pores of the AAO substrate and create thru-plane conductivity. To achieve conformal plating, the number of pre-treatment steps was optimized to prevent overplating and create a homogenous Ni deposit. Finally, with the creation of a conformally coated, conductive porous substrate, we can improve the efficiency and power output of TF-SOFC performance with commercially relevant active areas (larger than 1 cm2).

Sculpting conducting nanopore size and shape through de novo protein design.

Transmembrane β-barrels have considerable potential for a broad range of sensing applications. Current engineering approaches for nanopore sensors are limited to naturally occurring channels, which provide suboptimal starting points. By contrast, de novo protein design can in principle create an unlimited number of new nanopores with any desired properties. Here we describe a general approach to designing transmembrane β-barrel pores with different diameters and pore geometries. Nuclear magnetic resonance and crystallographic characterization show that the designs are stably folded with structures resembling those of the design models. The designs have distinct conductances that correlate with their pore diameter, ranging from 110 picosiemens (~0.5 nanometer pore diameter) to 430 picosiemens (~1.1 nanometer pore diameter). Our approach opens the door to the custom design of transmembrane nanopores for sensing and sequencing applications.

Scale translation yields insights into gas adsorption under nanoconfinement

This work describes a scale-translating simulation framework to investigate gas adsorption behavior in nanoconfined pores. The framework combines molecular simulations (MSs), equation of state (EoS), and lattice Boltzmann (LB) simulations. MSs reveal the physics of methane adsorption in nano-sized pores, where input values of fugacity coefficients are optimized based on EoS predictions. Then, an LB free-energy model, which incorporates a viral EoS, upscales intermolecular forces and estimates adsorption behavior via a proposed fluid–wall interaction model. Armed with the values of the LB interaction parameter as a function of pressure, the LB model is used to predict fluid behavior in irregular nanopores, and the results are validated against reference MS data. The LB model is then used to study adsorption behavior at a continuum scale in representative organic shale nanopores based on finely characterized Vaca Muerta shale samples. The results show that methane adsorption could significantly increase contained fluids by 10%–25% in pores smaller than 20 nm. However, in larger pores (40 nm to 90 nm), adsorption's impact diminishes to 2%–3%, suggesting sorption's negligible role beyond a 40 nm pore size.

Impact of nanopores in porous GaN on LED emission based on FDTD simulations

We simulated the light extraction efficiency (LEE) of porous GaN-based InGaN/GaN micrometer-sized light-emitting diodes (μLEDs) emitting within the visible wavelength range using the finite-difference time-domain (FDTD) method. The simulations show that the embedding of a porous GaN layer with 40 % porosity reduces the bottom LEE, while the top side LEE of the μLEDs is increased. In addition, it also exhibits complex scattering properties that affect the microcavity structure of these devices. The LEE and the degree of microcavity structure disruption are related to nanopore size and location. This association weakens with increasing wavelength. Also, a decrease in nanopore size corresponds to a diminished impact on μLED optical properties. Since the porous GaN layer contributes to the deposition of high-quality InGaN, controlling pore size of the porous GaN layer will aid the development of GaN-based red μLEDs and full-color displays.

Investigation of the usage of carbon-based two dimensional materials in lithium sulfide (Li–S) batteries

After the synthesis of graphene (Gr), the other two-dimensional (2D) allotropes of carbon based materials have been predicted theoretically or synthesized by experimentally. Two of these nanomaterials are graphyne (Gy) and graphdiyne (Gdy) which are close relatives of Gr and can be synthesized in bulk. While carbon atoms in Gr bonds with sp2 bonds, Gy and Gdy comprise sp and sp2 hybridized carbon atoms with high degrees of π conjugation that features uniformly distributed pores. So, these intrinsic nanopores add distinction to Gy and Gdy with respect to the Gr especially for energy storage applications. Nowadays, the researchers are studying to improve the storage capacity of Lithium-ion batteries (LIBs). However, Lithium–Sulfur (Li–S) batteries can store approximately five times more energy in terms of energy density compared to LIBs. In this study, we have systematically investigated the lithium polysulfides (LixSy; 1≤x≤2,1≤ y ≤ 8) adsorbed on Gr, Gy and Gdy monolayers by means of density functional theory (DFT) calculations. Our results reveal that, the presence of sp bonds and the size of nanopores in the structure extremely affect the adsorption energy of small sized LixSy clusters. However, the adsorption energies obtained with increasing the size of LixSy clusters are almost similar in Gr, Gy and Gdy monolayers. The diffusion barrier energy values obtained for LixSy clusters indicate that the migration of clusters on Gr may be easy but it is hard on Gdy and especially on Gy due to the pore networks in the structures acting as traps to anchor the LixSy clusters. In addition, we have investigated the double adsorption of LixSy clusters on Gr, Gy and Gdy structures to search the shuttle effect. It can be reported that LixSy clusters do not bind each others and do not create long polysulfide chains, which is not requested.