Micrometer-sized Pores Research Articles

Role of tactic response on the mobilization of motile bacteria through micrometer-sized pores

A major cause of high bioremediation endpoints is the limited bioaccessibility to residual contaminants resting in soil pores with diameters close to the size exclusion limit of bacterial cells. Under nongrowing conditions and in the absence of hydraulic flow, we examined how the tactic behavior of motile, contaminant-degrading Pseudomonas putida G7 cells (2 × 1 μm) influenced passage through membranes with pores ranging in size from 1 μm to 12 μm. The bacteria were spontaneously retained by the membranes - even those with the largest pore size. However, the cells were mobilized through 5 μm and 12 μm pores after the application of an attractant (salicylate). Mobilization also occurred by attraction to the common root exudate constituents γ-aminobutyric acid and citrate and repellence (or negative taxis) to zero-valent iron nanoparticles. The observed pore size threshold for tactic mobilization (5 μm) and unaltered cell fluxes and effective cell diffusion against different chemoeffector strengths and concentrations suggest that there is a physical constraint on the gradient sensing mechanism at the pores that drives the tactic response. Our results indicate that chemically mediated, small-scale tactic reactions of motile bacteria may become relevant to enhance the bioaccessibility of the residual contaminants present in micrometer-sized soil pores.

Kinetic Method of Producing Pores Inside Protein-Based Biomaterials without Compromising Their Structural Integrity.

Hydrogels made from globular proteins cross-linked covalently into a stable network are becoming an important type of biomaterial, with applications in artificial tissue design and cell culture scaffolds, and represent a promising system to study the mechanical and biochemical unfolding of proteins in crowded environments. Due to the small size of the globular protein domains, typically 2-5 nm, the primary network allows for a limited transfer of protein molecules and prevents the passing of particles and aggregates with dimensions over 100 nm. Here, we demonstrate a method to produce protein materials with micrometer-sized pores and increased permeability. Our approach relies on forming two competing networks: a covalent network made from cross-linked bovine serum albumin (BSA) proteins via a light-activated reaction and a physical network triggered by the aggregation of a polysaccharide, alginate, in the presence of Ca2+ ions. By fine-tuning the reaction times, we produce porous-protein hydrogels that retain the mechanical characteristics of their less-porous counterparts. We further describe a simple model to investigate the kinetic balance between the nucleation of alginate and cross-linking of BSA molecules and find the upper rate of the alginate aggregation reaction driving pore formation. By enabling a more significant permeability for protein-based materials without compromising their mechanical response, our method opens new vistas into studying protein-protein interactions and cell growth and designing novel affinity methods.

Preparation of glass-like carbon with micrometer-sized pores by mixing thermosetting resin with thermoplastic microbeads

Glass-like carbon (GLC) is an agranular carbon material with a pseudo-glass-like appearance on the surface and fractured face. In this study, GLCs with numerous micrometer-sized pores were prepared by mixing thermosetting resins with two sizes of thermoplastic microbeads. For these GLCs, the carbonization yields and apparent densities decreased when they were mixed with microbeads. SEM results suggested that the surfaces and fracture faces of GLCs mixed with small beads possess smaller pores compared to those prepared with large beads. The electrical resistances of GLCs with small beads heat-treated at 1000 ℃ or above were almost unchanged compared to those of the neat GLCs.

Polishing Characteristics and Mechanism of Polishing Glass Substrate Using Suede Pad with Fine Micrometer-Sized Pores

Chemical mechanical polishing (CMP) using a suede polishing pad is an essential fabrication process for glass substrates that require ultra-high planarization. However, the effect of surface asperities of the suede pad on its polishing characteristics is not completely understood because the structure of the suede pad in the thickness direction is not constant, and its surface asperities can easily change during the pad conditioning or marathon polishing processes. In addition, many previous studies have discussed the polishing mechanism using a suede pad; however, these studies used suede pads with a pore size of approximately 100 μm. This paper discusses the polishing characteristics of a suede pad with fine micrometer-sized pores by clarifying the relationships between the removal rate, friction coefficient, pore parameters, and roughness as the pad surface asperities. In this study, a series of marathon polishing tests were performed with and without conditioning. It was discovered that the removal rate was affected not only by the pore parameters but also by the surface roughness of the suede pad with fine pores. The relationship between the removal rate and the friction coefficient changed owing to the influence of pad conditioning, and this change is significant when the break-in conditioning time is short.

Pore Structure and Connectivity of Mixed Siliciclastic-Carbonate Tight Reservoirs in the Palaeogene from Qaidam Basin, NW China

The pore structure and connectivity in petroleum reservoirs are controlled in part by their petrological properties. Mixed siliciclastic-carbonate rocks have complex compositions and heterogeneous spatial distributions of the various minerals. As a result, the study of the pore structure and connectivity of mixed siliciclastic-carbonate tight reservoirs has been limited. In this study, methods such as thin section microscopy, X-ray diffraction, X-ray computed tomography, low pressure N2 adsorption, and spontaneous imbibition were adopted to comprehensively analyze the petrological properties, pore structure, and connectivity of the mixed siliciclastic-carbonate tight reservoirs in the upper member of the Xiaganchaigou Formation in the Yingxi Area, Qaidam Basin. The results showed that micrometer-sized pores in mixed siliciclastic-carbonate tight reservoirs are mainly dissolution pores, and that the spatial distribution of the pores is highly heterogeneous. The average pore radius range, average throat radius range, and average coordination number range of micronmeter-sized pores are 2.09~3.42 μm, 1.32~2.19 μm, and 0.48~1.49, respectively. Restricted by the concentrated distribution of local anhydrite, the connectivity of micronmeter-sized pores develops well only in the anhydrite, showing negligible contribution to the overall reservoir connectivity. In contrast, nanometer-sized pores in the mixed siliciclastic-carbonate tight reservoirs are mainly intercrystalline pores in dolomite. The range of nanometer-sized pores diameters is mainly distributed in 1.73-31.47 nm. The pores have a smooth surface, simple structure, and relatively homogeneous spatial distribution. The dissolution of dolomite intercrystalline pores by acidic fluids increases the connectivity of the nanometer-sized pores. This paper presents genetic models for microscopic pore structures and connectivity of mixed siliciclastic-carbonate rocks, making possible the evaluation on the quality of the mixed siliciclastic-carbonate tight reservoirs.

Localizing Phosphoric Acid in High-Temperature PEM Fuel Cell Catalyst Layers Using Cryostatic Focused Ion Beam Scanning Electron Microscopy

Phosphoric acid serves as a proton conductor in high-temperature PEM fuel cells (HT-PEMFCs). The Membrane Electrode Assembly (MEA) consists of a phosphoric acid doped polybenzimidazole (PBI) membrane sandwiched between two gas diffusion electrodes (GDEs). During cell activation, phosphoric acid percolates from the membrane into the GDEs. Thereby, the acid should distribute homogeneously over the entire catalyst layer to ensure sufficient proton conductivity. Understanding phosphoric acid distribution in the porous GDE is essential to achieve high-performing HT-PEMFCs.The phosphoric acid distribution in HT-PEMFC GDEs was previously investigated using impedance spectroscopy combined with the distribution of relaxation times analyses1. This study shows the significant impact of the catalyst nanostructure on phosphoric acid distribution. Additionally, NMR experiments indicate the wetting of the nanometer-sized pores when a GDE comes in contact with liquid phosphoric acid2. Employing energy-dispersive X-ray spectroscopy (EDS), different types of gas diffusion layers were evaluated3. A gas diffusion layer with smaller pore sizes was identified to increase the acid migration out of the cell. Furthermore, a uniform phosphoric acid distribution in both catalyst layers was determined with electron probe micro-analysis (EPMA) after operating a HT-PEMFC cell for 12,000 h4.In this work, the phosphoric acid distribution within GDEs is determined employing cryostatic focused ion beam scanning electron microscopy (cryo FIB-SEM) coupled with energy-dispersive X-ray spectroscopy (EDX) and time-of-flight secondary ion mass spectroscopy (TOF-SIMS). By combining these methods, the location of phosphoric acid can be directly linked to the morphology of the catalyst layer.In-house fabricated spray-coated GDEs were assembled to an MEA and heated up to operating temperature to simulate the cell activation. After five days, a typical activation period, the cell was disassembled. Thereby, the cathode GDE was separated from the membrane. The GDE was submerged in liquid nitrogen to prevent redistribution of phosphoric acid. This method allows handling phosphoric acid under UHV conditions.Phosphoric acid could be detected both on the surface and in the bulk of the catalyst layer (Figure 1). It was found that the acid invades mainly the nanometer-sized pores, not the larger, micrometer-sized pores. These experiments confirm earlier results, which predicted preferential wetting of smaller pore walls using NMR experiments1. The acid can reach the catalyst particles housed inside nanometer-sized pores and contribute to the electrochemically active surface area of the cell.References N. Bevilacqua et al., J. Power Sources Adv., 7, 100042 (2021).E. Zhang et al., Chem. Commun., 57, 2547–2550 (2021).A. Kannan, Q. Li, L. N. Cleemann, and J. O. Jensen, Fuel Cells, 18, 103–112 (2018).Y. Oono, A. Sounai, and M. Hori, J. Power Sources, 210, 366–373 (2012). Figure 1

Terahertz Birefringent Biomimetic Aerogels Based on Cellulose Nanofibers and Conductive Nanomaterials.

Biomimetic, lamellar, and highly porous transition-metal carbide (MXene) embedded cellulose nanofiber (CNF) aerogels are assembled by a facile bidirectional freeze-drying approach. The biopolymer aerogels have large-scale, parallel-oriented micrometer-sized pores and show excellent mechanical strength and flexibility, tunable electrical properties, and low densities (2.7-20 mg/cm3). The CNF, MXene, and lamellar pores are efficiently utilized to endow the aerogels with exceptionally high birefringence in the terahertz (THz) regime. Birefringence values as high as 0.09-0.27 at 0.4 THz are achieved, which is comparable to most commercial THz birefringent materials such as liquid crystals, which suffer from fast disintegration, high cost, and complicated preparation processes. Empirical modeling for different MXene contents and an experimental comparison with silver nanowire or carbon nanotube embedded CNF aerogels suggest that the intrinsic conductivity and content of embedded nanomaterials, the aerogel porosity, and the lamellar cell walls can affect the optical properties such as the THz birefringence and absorption. The determination of optical anisotropy in the biopolymer aerogels lays a foundation for further exploration of ultralight, freestanding, and low-cost biomimetic porous architecture-based THz devices.

Diagenesis of the Malmian Mikulov Formation source rock, Vienna Basin: Focus on matrix and pores

Diagenetic processes and pore development in the matrix of the 1000 m thick main source rock for oil and gas in the Vienna Basin, the autochthonous Malmian mudstones of the Mikulov Formation have been studied. Core samples from wells over a true vertical depth range of 1400 m–8551 m were available. The bulk samples contain quartz, minor amounts of plagioclase, pyrite and a large but variable proportion of calcite; the clay mineral content ranges from 14 to 47%. The clay fraction contains a prominent illite-smectite (I–S) mixed-layer phase, illite, chlorite and kaolinite. The quantities of I–S and kaolinite decrease with depth, whereas illite and chlorite increase with depth. Diagenesis has involved a gradual transformation of smectite to illite through mixed-layer I–S intermediates. The ordering of the mixed layer I–S changes with increasing depth from R0 to R1 and R3. The R1 transformation of the mixed-layer I–S occurs at approximately 3000 m and vitrinite reflectance values of 0.4%–0.6%. Based on petrographic evidence, the cations resulting from the illitization of smectite were the source of a variety of late diagenetic mineral cements, such as Fe and Mg for chlorite formation and for ferroan dolomite precipitation. Illitization also provided Si for local quartz cementation. During diagenesis nanometer to micrometer size pores developed because of specific mineral frameworks and dissolution processes. Organic matter pores developed in deeper, thermally mature samples. Phyllosilicate framework pores between brittle grains are commonly observed. Pores caused by partial dissolution of carbonate grains also occur. In places diagenetic cements, such as quartz overgrowths or carbonate cements keep pores propped open. The connectivity of the pores cannot be established unequivocally from SEM photomicrographs, but they likely contribute to the creation and preservation of effective porosity and gas storage capacity of these rocks.

Laser-assisted nanowetting (LAN): Hierarchical Nanocomposites containing polymer/gold nanorods on breath figure films

Polymer nanostructures have drawn tremendous interest in recent years owing to their unique properties and widespread applications in various fields. It is still a great challenge, however, to develop novel methods that are capable of preparing hierarchical polymer structures with patterning ability. To conquer this challenge, in this work, we demonstrate the fabrication of hierarchical structures containing polystyrene (PS)/gold nanorods (AuNRs) by combining the modified breath figure method and the laser-assisted nanowetting (LAN) method. PS/PS-AuNRs films are dipped into good/poor solvents (CHCl3/MeOH) mixture solutions using the modified breath figure method to form the porous films with micrometer-sized pores. Subsequently, the porous films are brought in contact with anodic aluminum oxide (AAO) templates and shone by laser beams. The AuNRs then absorb the laser energy and heat the surrounding polymer chains via plasmonic heating, inducing the PS chains to wet the nanopores of the AAO templates. As a result, hierarchical PS/PS-AuNRs films with controlled regions and dimensions can be obtained. This study opens a new research direction for developing hierarchical polymer structures using porous templates.

Fiber-based BN aerogels for efficient and cross-scale removals of microorganisms and pollutants in water

Water purification is an important issue in our daily life. Various pollutants, from micrometer-sized microorganisms to molecular- or atomic-sized pollutants, need to be efficiently removed from water. Unlike traditional cascade-stage techniques, we report a one-step water purification method based on a ceramic aerogel composed of porous BN fibers, which realizes >99% Microcystis and >98% E. coli cell removals from water and high-capacity adsorptions of pesticide, oils, organic compounds, metal ions, etc. The adsorption capacities for metal ions are about one order of magnitude higher than those achieved by the reported porous/activated carbons. Our studies show the importance of the unique hierarchical structure of the BN aerogel to realize remarkable water purification performances; micrometer-sized pores constructed by high-dense fibers, the porous structures and rich surface functional groups of the BN fibers all contribute to the efficient removals of different types of the pollutants. These results suggest the potential applications of the BN aerogels toward one-step and comprehensive water purifications.

Porous Optically Transparent Cellulose Acetate Scaffolds for Biomimetic Blood-Brain Barrierin vitro Models.

In vitro blood-brain barrier (BBB) models represent an efficient platform to conduct high-throughput quantitative investigations on BBB crossing ability of different drugs. Such models provide a closed system where different fundamental variables can be efficaciously tuned and monitored, and issues related to scarce accessibility of animal brains and ethics can be addressed. In this work, we propose the fabrication of cellulose acetate (CA) porous bio-scaffolds by exploiting both vapor-induced phase separation (VIPS) and electrospinning methods. Parameters of fabrication have been tuned in order to obtain porous and transparent scaffolds suitable for optical/confocal microscopy, where endothelial cell monolayers are allowed to growth thus obtaining biomimetic BBB in vitro models. Concerning VIPS-based approach, CA membranes fabricated using 25% H2O + 75% EtOH as non-solvent showed submicrometer-scale porosity and an optical transmittance comparable to that one of commercially available poly(ethylene terephthalate) membranes. CA membranes fabricated via VIPS have been exploited for obtaining multicellular BBB models through the double seeding of endothelial cells and astrocytes on the two surfaces of the membrane. Electrospun CA substrates, instead, were characterized by micrometer-sized pores, and were unsuitable for double seeding approach and long term studies. However, the potential exploitation of the electrospun CA substrates for modeling blood-brain-tumor barrier and studying cell invasiveness has been speculated. The features of the obtained models have been critically compared and discussed for future applications.

3D printing of inherently nanoporous polymers via polymerization-induced phase separation

3D printing offers enormous flexibility in fabrication of polymer objects with complex geometries. However, it is not suitable for fabricating large polymer structures with geometrical features at the sub-micrometer scale. Porous structure at the sub-micrometer scale can render macroscopic objects with unique properties, including similarities with biological interfaces, permeability and extremely large surface area, imperative inter alia for adsorption, separation, sensing or biomedical applications. Here, we introduce a method combining advantages of 3D printing via digital light processing and polymerization-induced phase separation, which enables formation of 3D polymer structures of digitally defined macroscopic geometry with controllable inherent porosity at the sub-micrometer scale. We demonstrate the possibility to create 3D polymer structures of highly complex geometries and spatially controlled pore sizes from 10 nm to 1000 µm. Produced hierarchical polymers combining nanoporosity with micrometer-sized pores demonstrate improved adsorption performance due to better pore accessibility and favored cell adhesion and growth for 3D cell culture due to surface porosity. This method extends the scope of applications of 3D printing to hierarchical inherently porous 3D objects combining structural features ranging from 10 nm up to cm, making them available for a wide variety of applications.

Adjustable polystyrene nanoparticle templates for the production of mesoporous foams and ZnO inverse opals

The manifold applications of porous materials, such as in storage, separation, and catalysis, have led to an enormous interest in their cost-efficient preparation. A promising strategy to obtain porous materials with adjustable pore size and morphology is to use templates exhibiting the appropriate nanostructure. In this study, close-packed polystyrene (PS) nanoparticles, synthesized by emulsion polymerization, were used to produce porous PS and ZnO inverse opals. The size and distribution of the polystyrene nanoparticles, characterized by dynamic light scattering (DLS), small-angle neutron scattering (SANS), and scanning electron microscopy (SEM), were controlled via the concentration of sodium dodecyl sulfate (SDS). Systematic measurements of the water/styrene-interfacial tension show that the critical micelle concentration (CMC) of the ternary water–styrene–SDS system, which determines whether monodisperse or polydisperse PS particles are obtained, is considerably lower than that of the binary water–SDS system. The assemblies of close-packed PS nanoparticles obtained via drying were then studied by small-angle X-ray scattering (SAXS) and SEM. Both techniques prove that PS nanoparticles synthesized above the CMC result in a significantly unordered but denser packing of the particles. The polystyrene particles were subsequently used to produce porous polystyrene and ZnO inverse opals. While the former consists of micrometer-sized spherical pores surrounded by extended open-cellular regions of mesopores (Rpore ≈ 25 nm), the latter are made of ZnO-nanoparticles forming a structure of well-aligned interconnected pores.Graphical abstract

Syntheses of Colorless and Transparent Polyimide Membranes for Microfiltration.

Herein, poly(amic acid) (PAA) was synthesized using 4,4’-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) as a dianhydride and 2,2-bis(3-aminophenyl)hexafluoropropane (6FAm) and 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane (6FAm-OH) as diamines. Poly(vinyl alcohol) (PVA) at various contents (0–5.0 wt%) was blended with PAA to prepare a composite material. Then, colorless and transparent polyimide (CPI) composite films were prepared by applying various stages of heat treatment using the PAA/PVA blend film as a precursor. These film-type composites were immersed in water to completely dissolve PVA, a water-soluble polymer, and their pore sizes were investigated to determine their potential as a porous membrane. According to the results of scanning electronic microscopy (SEM), as the concentration of PVA increased from 0 to 5.0 wt% in the CPI/PVA composite films, the size of the pores resulting from the dissolution of water-soluble PVA increased. Further, the micrometer-sized pores were uniformly dispersed in the CPI films. The thermal properties, morphology, and optical transparency of the two types of CPI membranes synthesized using 6FAm and 6FAm-OH monomers were examined and compared.

Volatile-Organic-Compound-Intercepting Solar Distillation Enabled by a Photothermal/Photocatalytic Nanofibrous Membrane with Dual-Scale Pores.

Solar distillation is emerging as a robust and energy-effective tool for water purification and freshwater production. However, many water sources contain harmful volatile organic compounds (VOCs), which can evaporate through the photothermal evaporators and be collected together with distilled water, or even be enriched in the distilled water. In view of the penetration of volatile organic compounds, herein, we rationally demonstrate a dual-scale porous, photothermal/photocatalytic, flexible membrane for intercepting volatile organic compounds during solar distillation, which is based on a mesoporous oxygen-vacancy-rich TiO2-x nanofibrous membrane (m-TiO2-x NFM). The dual-scale porous structure was constructed by micrometer-sized interconnected tortuous pores formed by the accumulation of m-TiO2-x nanofibers and nanometer-sized pores in the m-TiO2-x individual nanofibers. Consequently, the membrane can sustainably in situ intercept VOCs by providing more photocatalytic reactive sites for collision (mainly by mesopores) and longer tortuous channels for prolonging VOC retention (mainly by micrometer-sized pores); thus, it results in less than 5% of phenol residual in distilled water. As a proof of concept, when the m-TiO2-x NFM is employed to purify practical river water in an evaporation prototype under real solar irradiation, complex volatile natural organic contaminants can be effectively intercepted and the produced distilled water meets the drinking water standards of China. This development will promote the application prospects of solar distillation.

Pore-size and polymer affect the ability of filters for washing-machines to reduce domestic emissions of fibres to sewage.

When clothes are worn and washed, they emit fibres into the ecosystem via discharges of sewage that have been linked to the global dispersion of clothing fibres. Facilities that treat sewage divert some fibres from sewage effluent to sludge, but no current methods of filtration eliminate their environmental release. While filters for washing-machines are sold to consumers with the argument they will reduce the emissions of fibres from clothes to the environment, there is insufficient scientific peer-reviewed evidence assessing their ability to retain fibres from washed clothes and reduce environmental contamination. To improve our understanding and develop more realistic methods to assess the efficiency of filters, we washed replicate cotton and polyester garments in replicate domestic front-loaded washing-machines with and without replicate filters (micro- and milli-meter-sized pores), and then quantified the masses of the fibres retained by the filters and those released in the effluent. Here we show micrometer-sized filters significantly reduced the mass of cotton by 67% (F2,6 = 11.69, P<0.01) compared to effluent from appliances with no filters, whilst filters in general reduced polyester fibres in their effluent by more than 65% (micrometer-sized pores) and 74% (millimeter-sized pores) compared to effluent from appliances with no filters (F2,12 = 5.20, P<0.05). While filters with micrometer-sized pores caught larger masses and total proportions of fibres than filters with millimeter-sized pores, the differences were only significant for the total proportions of cotton (t = 4.799 df = 4, P<0.01). For tests with garments of either types of polymer, the filtered effluent still contained up to a third of the original masses of fibres released from the garments. Given the diversity of clothes, polymers, appliances and filters currently sold to consumers, our work shows the value of increasing the rigour (e.g. more levels of replication) when testing filters and the need for further studies that test an even greater diversity of materials and methods in order to meet the growing demand for knowledge from governments, industry and the public.

Mechanisms of lipid preservation in archaeological clay ceramics revealed by mass spectrometry imaging

Traces of lipids, absorbed and preserved for millennia within the inorganic matrix of ceramic vessels, act as molecular fossils and provide manifold information about past people's subsistence, diet, and rituals. It is widely assumed that lipids become preserved after adsorption into nano- to micrometer-sized pores, but to this day the distribution of these lipids in the ceramics was virtually unknown, which severely limits our understanding about the process of lipid preservation. Here we use secondary ion mass spectrometry (SIMS) imaging for direct in situ analysis of lipids absorbed in 700- to 2,000-y-old archaeological pottery. After sectioning from larger sherds, wall cross-sections of smaller fragments were used for SIMS analysis. Lipids were found in relatively large zones of 5- to 400-µm diameter, which does not support the notion of absorption only into individual nanometer-scale pores but indicates that more macroscopic structures in the ceramics are involved in lipid preservation as well. Furthermore, lipids were found concentrated on calcium carbonate inclusions in the ceramics, which suggests that precipitation of fatty acids as calcium salts is an important aspect of lipid preservation in archaeological samples. This has important implications for analytical methods based on extraction of lipids from archaeological ceramics and needs to be considered to maximize the yield and available information from each unique sample.

Ir Decorated Fractal Ni Catalysts for the Oxygen Evolution Reaction

Porous and fractal Ni electrode synthesized by the Dynamic Hydrogen Bubbling Template (DHBT) method (Ni DHBT electrode) have shown very promising performances for the oxygen evolution reaction (OER) in alkaline electrolyte. This was thought to arise as a result of the extended electrochemical active surface area and its superaerophilic properties that facilitates the release of oxygen bubbles[1]. Herein, we report on a method to decorate the Ni DHBT electrode with Ir atoms via a galvanic replacement (GR) reaction. The resulting electrode has very low loadings of Ir (0.26 atom % as determined by EDX). As shown in Figure 1, micrometer-sized pores are observed at the surface of deposits, with pore walls exhibiting a highly porous cauliflower-like secondary structure, with much smaller pore diameter (typically less than 500 nm). The structure seen in Figure 1 was observed over the entire 0.32 cm2 geometric surface area of the deposits. The morphology of the Ir-modified electrode is not changed with respect to Ni DHBT electrode, indicating that the GR reaction is occurring only at the surface of the deposit. Voltammetry cyclic tests in 1M KOH solution showed hydrogen adsorption/desorption (Hupd) peaks of Ir as well as the redox peaks of Ni(OH)2 which suggested the coexistence of Ir and Ni content at electrode/electrolyte interface. The activity for the OER of Ni DHBT electrode was further improved by decoration with Ir, resulting in an overpotential of 195mV at 10 mA/cm2 and a Tafel slope of 46 mV/dec. To the best of our acknowledgment, this is one of the best performing Ni based OER catalysts reported so far. The interaction of oxygen bubbles with the electrode surface will also be assessed using both optical imaging and acoustic emission characterization.[1] M. Hao et al., “Hydrogen Bubble Templating of Fractal Ni Catalysts for Water Oxidation in Alkaline Media,” ACS Appl. Energy Mater., vol. 2, no. 8, pp. 5734–5743, Aug. 2019. Figure 1

Calculation of full three-dimensional silicon detectors with stacking micrometer-sized pores for improving thermal neutrons detection

3D semiconductor detectors of thermal neutrons are facing difficulties on coating, filling and coating in its deep pores of hundred micrometers. This paper presents a way of stacking shallow pores of several micrometers to avoid the deep-pore technologies, as well as to improve thermal neutrons detection. The full 3D configurations of silicon detectors were achieved by stacking the shallow-pores layers. 6LiF and 10B converters were filled in the pores or interlayers of the multilayered pores-arrays. Detection efficiency and energy deposition spectra were calculated with Geant4 code. The results show the full 3D detectors are featured with higher detection efficiency and wider energy-deposition-spectra than the reported data. With 300 keV LLD, the maxima of the detection efficiencies are 88% and 60% for 6LiF and 10B, respectively, in the configurated parameters. And the energy deposition spectra of secondary particles in the detector are shifted from the low- to high-energy side by multilayering the shallow-pores-arrays on silicon.

Shaking-assistant hydrothermal synthesis of hierarchical SiO2/expanded graphite composite and its application in water treatment

A novel hierarchical mesoporous SiO2/expanded graphite (EG) composite was synthesized through a special shaking-assistant hydrothermal method. This composite had a unique structure with combined micrometer-sized pores from the EG and nanometer-sized mesopores from the silica. Structure ordering, surface area, and morphology of this composite strongly depended on the amount of siliceous source. The SiO2/EG composite had a greatly enhanced adsorption capability (72 mg·g−1), fast adsorption rate, and high adsorption intensity (KL = 2.172) for the removal of methylene blue from aqueous solutions. This work proposed a potential technique of developing composite materials and their related applications in environmental fields.