Nanoporous membranes produced from polycrystalline Ni-based superalloys

Porous metal membranes are produced from a two phase system in which the discrete cubic gamma'-precipitates connect during self assembly. In the so called rafting process the cubic particles start to coarsen and finally create a network within the gamma-matrix. In a following electrochemical leaching process one of the phases can be removed leaving the nanoporous membrane. So far, single crystalline alloys have been used for producing thin nanoporous membranes. Now research is in progress to produce the nanoporous membranes from polycrystalline alloys in a creep process. A modification of the commercially available alloy Nimonic 115 was used for these membranes. The permeability of these membranes was proven in a gas-flow test.     

聚合物乳液粒子制备纳米多孔增透膜

采用提拉法在载玻片上沉积了PMMA/PS混合乳液粒子,用环己烷选择性地溶解掉表层PS粒子,制备了孔隙率从表向里梯度变化的纳米粒子增透膜,在578 nm处透过率可达99.5%;研究了两种聚合物纳米粒子的比例及环己烷浸泡时间对增透性能的影响。本方法可用于大面积和不规则基材上制备增透膜,并解决了提拉法成膜的粒子堆积紧密、孔隙率低且不易调节的缺点,使粒子膜的透过率大幅度提高。     

General model of hydrogen transport through nanoporous membranes

A general model of transport of gases in solid nanoporous membranes was established. The model was developed based on Dusty Gas Model (DGM), solution diffusion and surface diffusion. As a result, solutions of the model for different transport conditions were derived. In this investigation, parameters of hydrogen gas transport of vinyl film (polymer) and vycor glass membranes were used to calculate semi-empirical solutions of the general model. In other words, the solutions of the general model were analytically obtained for different transport conditions, using experimentally obtained parameters of hydrogen gas transport in vinyl film (polymer) and vycor glass membranes. The obtained solutions of the general model were for the hydrogen transport of the membranes in the non-porous, nanoporous, microporous, and to macroporous range. The model was found useful for predictions of hydrogen transport through solid membranes. Additionally the model can be ready used for other gases for predictions of the transport of gases in nanoporous membranes.     

Suspended nanoporous membranes as interfaces for neuronal biohybrid systems

A biohybrid system composed of neuronal cells and silicon-supported nanoporous membranes has been designed to facilitate control of the biochemical environment of neuronal networks with cellular resolution. The membranes may exhibit variable pore sizes and interpore distances and are interfaced to a microfluidic device. Different porosity parameters give rise to changes in the transconductance of the nanopores and can therefore be used to control diffusion of molecules through the membranes. It was shown that the porous membranes are biocompatible with primary vertebrate as well as insect neurons. Our results indicate that nanoporous membranes may be used to interface with biological materials in a biohybrid system, for example as an artificial chemical synapse interface.     

Quartz crystal impedance response of nonhomogenous composite electrodes in contact with liquids

A new model of quartz-crystal impedance (QCI) of nonuniform layers composed of bumps of carbon particles (either porous or nonporous) and a polymeric binder layer has been proposed. The solid particles are modeled by semispherical and oblate semispheroid bumps embedded into the "sea" of a polymeric binder layer. On the basis of this model and elaborating on the principles of hydrodynamic spectroscopy of composite electrode materials, the geometric and porous structure parameters of nanoporous carbon and nonporous graphite composite electrodes in contact with liquids have been reliably determined. This work is believed to create a solid theoretical background for both advanced studies and optimized formulations of the composite electrodes suited to practical electrochemical devices and for the interpretation of the processes of ions and solvent insertion into nanoporous carbon electrodes uniquely probed by the QCI method (supercapacitive cells, desalination membranes).     

Optical detection of ion-channel-induced proton transport in supported phospholipid bilayers

The integration of ion-channel transport functions with responses derived from nanostructured and nanoporous silica mesophase materials is demonstrated. Patterned thin-film mesophases consisting of alternating hydrophilic nanoporous regions and hydrophobic nanostructured regions allow for spatially localized proton transport via selective dimerization of gramicidin in lipid bilayers formed on the hydrophilic regions. The adjoining hydrophobic mesostructure doped with a pH sensitive dye reports the transport. The ease of integrating functional membranes and reporters through the use of patterned mesophases should enable high throughput studies of membrane transport.     

Antibacterial activity of zinc oxide-coated nanoporous alumina

Nanoporous alumina membranes, also known as anodized aluminum oxide membranes, are being investigated for use in treatment of burn injuries and other skin wounds. In this study, atomic layer deposition was used for coating the surfaces of nanoporous alumina membranes with zinc oxide. Agar diffusion assays were used to show activity of zinc oxide-coated nanoporous alumina membranes against several bacteria found on the skin surface, including Bacillus subtilis, Escherichia coli, Staphylococcus aureus, and Staphylococcus epidermidis. On the other hand, zinc oxide-coated nanoporous alumina membranes did not show activity against Pseudomonas aeruginosa, Enterococcus faecalis, and Candida albicans. These results suggest that zinc oxide-coated nanoporous alumina membranes have activity against some Gram-positive and Gram-negative bacteria that are associated with skin colonization and skin infection.     

Novel magnetite-silica nanocomposite (Fe3O4-SBA-15) particles for DNA binding and gene delivery aided by a magnet array

Novel magnetite-silica nanocomposite particles were prepared using SBA-15 nanoporous silica as template. Magnetite nanoparticles were impregnated into the nanopore array of the silica template through thermal decomposition of iron(III) acetylacetonate, Fe(AcAc)3 at 200 degrees C. These composite particles were characterized using TEM, XRD and SQUID magnetometry. The TEM images showed that the size of composite particles was around 500 nm and the particles retained the nanoporous array of SBA-15. The formation of magnetite nanoparticles was confirmed by the powder XRD study. These composite particles also exhibited ferrimagnetic properties. By coating with short chain polyethyleneimine (PEI), these particles are capable of binding DNA molecules for gene delivery and transfection. With an external magnetic field, the transfection efficiency was shown to have an increase of around 15%. The results indicated that these composite nanoparticles may be further developed as a new tool for nanomagnetic gene transfection.     

Hydroxyapatite formation on metallurgical grade nanoporous silicon particles

Studies into bone-like apatite or hydroxyapatite (HA) growth on potential biomaterials when in contact with simulated body fluid (SBF) not only establish a general method for determining bioactivity but coincidently lead to the design of new bioactive materials in biomedical and tissue engineering fields. Previous studies of HA growth on porous silicon (PS) have examined electrochemically etched silicon substrates after immersion in a SBF. This study differs from previous work in that it focuses on characterising HA growth on chemically etched metallurgical grade nanoporous silicon particles. The PS used in this study is comprised of nanosponge particles with disordered pore structures with pore sizes ranging up to 10 nm on micron-sized particles. The silicon particles are analysed before and after immersion into SBF using scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray (EDX) analysis and X-ray photoelectron spectroscopy (XPS). Results indicate that a HA layer forms on the surface of the nanosponge particles. Experimental analysis indicates that the morphology and calcium-to-phosphorus ratio (Ca/P) verify the formation of crystalline HA on the nanoporous silicon particles.     

Characterization of nanoporous structures of polyphenylene oxide derived carbon membranes by means of 129Xe NMR

The 129Xe NMR spectroscopy has become a powerful technique of materials characterization because the xenon atom has a very large polarizability. It is well known that the signal of xenon sorbed in porous media is sensitively affected by the surrounding environments such as the chemistry of material surface. In this study, the pore properties of nanoporous PPO (polyphenylene oxide) derived carbon membranes were characterized by means of the variable temperature (VT)-hyperpolarized Xe NMR. The Xe NMR results showed good agreements with the adsorption results of CO2 for the PPO derived nanoporous carbon membranes. It was clearly shown that the 129Xe NMR could be used as one of the promising characterization methods of nanoporous materials with low surface area and small pore volume.     

甘蔗渣基纳米孔碳在超级电容器中的应用(英文)

以甘蔗渣为原料,采用微波化学活化法制备了一类纳米孔碳,并将其用作离子液体超级电容器的电极材料。采用氮气吸附、扫描电子显微镜和透射电子显微镜等手段对制备的纳米孔碳进行系统的结构表征。结果表明,当氯化锌溶液的浓度从20%增大到60%时,所制备的纳米孔碳的孔径从2.5nm增加到7.0nm,这说明纳米孔碳的孔径可以简单地通过控制氯化锌溶液的浓度来调节。通过循环伏安、恒流充放电和电化学阻抗等方法测试纳米孔碳作为离子液体超级电容器电极材料时的电化学性质。研究结果表明,在离子液体中纳米孔碳的电容性能与其孔径紧密相关,纳米孔碳的孔尺寸越大,电容性能越好。     

Nanoporous silica membranes fabricated using multiwalled carbon nanotubes

Nanoporous silica membranes were fabricated using 3-aminopropyltriethoxysilane (APS) and acyl chloride-functionalized multiwalled carbon nanotubes (MWCNTs). The amine groups of silane reacted with the functional groups (e.g., acid chloride) that were attached to the sidewall of the MWCNTs. The APS that was grafted to the sidewall of the MWCNTs was polymerized in order to coat the MWCNTs wall through heating. The thickness of the silica layer on the surface of the MWCNTs was controlled by adjusting the growth time of the SiO2 layer. Approximately 20 nm-sized pores were formed through the removal of the MWCNTs using a simple thermal process, but some traces of the MWCNTs still remained. The porous properties of the nanoporous silica membrane were analyzed from the nitrogen adsorption-desorption isotherms that were obtained using a surface area and porosimetry analyzer. The structure and composition of the silane-modified MWCNTs were characterized using scanning electron microscopy, energy dispersive spectroscopy and transmission electron microscopy.     

Single-step synthesis of nanoporous silica colloids

Nanoporous silica colloids were prepared by a convenient single-step sol-gel process. In this approach, acidic aluminum nitrate (Al(NO₃)₃) solution was added to the ethanol solution of tetraethoxy orthosilicate (TEOS). In the preliminary stage, alumina/silica core-shell particles were formed. Then the Al₂O₃ cores were dissolved subsequently with the decrease of pH value, and the nanoporous silica was formed. The porous silica particles were characterized by transmission electron microscopy (TEM). The formation mechanism of the porous silica was discussed.     

Electrically conductive hexagonally ordered nanoporous membranes produced by ion-beam induced carbonization of block-copolymer precursors

Highly ordered carbonized nanoporous membranes are produced by ion-beam treatment of self-assembled block copolymer precursor films. The membranes are electrically conductive, as verified by scanning tunnelling microscopy (STM) measurements. The carbonization degree is investigated by means of Raman and infrared (IR) spectroscopy, and the morphology of the films via transmission electron microscopy (TEM). Domains of perfect hexagonal order of the pores are visualized via digital interference of a TEM image of a membrane with computer-generated triangular lattices, producing specific moiré fringes. This novel material could be interesting for applications in nano-catalysis, micro-electronics, and as the grid for STM and TEM imaging of free-standing nano-objects.     

Synthesis and characterization of nanoporous silica using dendrimer molecules

A water soluble porogen, e.g., poly(amido amine) dendrimer, has been used as a structure-directing agent to introduce porosity of nanometer scale in silica-based nanocomposite materials. Hydrothermal synthesis was carried out at different elevated temperatures (343-413 K) in a closed teflon-lined stainless steel autoclave under autogenerated pressure. The synthesis time varied from 2 to 6 days, depending upon pH, synthesis temperature, concentration of porogen, etc. X-ray diffraction, transmission and scanning electron microscopic analyses, as well as infrared absorption spectroscopic measurements, were carried out to characterize these materials. Mostly disordered mesostructures were observed. The porous silica particles with sphere-like morphology varied from 30 to 200 nm in size were prepared depending upon the conditions of preparation. The structure and nanoporosity were preserved after the removal of structure-directing porogen through calcination at 823 K. The pore size was in the range of the dendrimer molecule as a template, indicating the structure-directing role of the terminal amino groups in the dendrimer molecule for the synthesis of nanoporous silica, since the nanoporous silica could be prepared by the hydrogen bonding or electrostatic interaction of dendrimer amino groups and tetraethyl orthosilicate.     

Confinement Impact for the Dynamics of Supported Metal Nanocatalyst

Supported metal nanoparticles play key roles in nanoelectronics, sensors, energy storage/conversion, and catalysts for the sustainable production of fuels and chemicals. Direct observation of the dynamic processes of nanocatalysts at high temperatures and the confinement of supports is of great significance to investigate nanoparticle structure and functions for practical utilization. Here, in situ high‐resolution transmission electron microscopy photos and videos are combined with dynamics simulations to reveal the real‐time dynamic behavior of Pt nanocatalysts at operation temperatures. Amorphous Pt surface on moving and deforming particles is the working structure during the high operation temperature rather than a static crystal surface and immobilization on supports as proposed before. The free rearrangement of the shape of Pt nanoparticles allows them to pass through narrow windows, which is generally considered to immobilize the particles. The Pt particles, no matter what their sizes, prefer to stay inside nanopores even when they are fast moving near an opening at temperatures up to 900 °C. The porous confinement also blocks the sintering of the particles under the confinement size of pores. These contribute to the continuous high activity and stability of Pt nanocatalysts inside nanoporous supports during a long‐term evaluation of catalytic reforming reaction.     

Preparation of nanoporous SiO2 particles and their application in drug release control

Nanoporous SiO2 particles which have different pore size and volume were prepared from a colloidal mixture of nano-sized silica particles by a spray heating method. The prepared nanoporous SiO2 particles were employed as a drug carrier to investigate the release behaviors of methylene blue (MB) as a model drug for a selected period of time. The concentration of released MB from the porous particles was measured by a UV-Vis spectroscopy with respect to time. The release of MB from the porous particles was maintained for 400 hours and the maximum amount of the released MB was 0.8 mg at 1.56 cm3/g of pore volume. As pore volume of the nanoporous particles increased, the release rate of MB increased.     

Molecular discrimination inside polymer nanotubules

Recognition of small organic molecules and large biomolecules such as proteins is of great importance in pharmaceutical as well as biological applications. Recognition inside a nanoporous membrane is particularly attractive, because of the advantages associated with ligand-receptor interactions in confined spaces. Classical nanoporous membrane-based separations simply use the difference in size of the analytes relative to pore size in the membrane. In order to bring about selectivity beyond size, it is necessary that methods for functionalizing the membrane pores are readily available. Here, we describe a simple approach to functionalize the nanopores within these membranes using self-assembling and non-self-assembling polymers. We show that these modified membranes separate small molecules based on size, charge and hydrophobicity. We also demonstrate here that proteins can be differentially transported through the nanopores based on their size and/or electrostatics.     

Role of alumina nanoporosity in acute cell response

This work studied the effect of nanoporous alumina in acute cellular response in an in vivo model. Nanoporous alumina membranes, with pore size diameters of 20 and 200 nm, were fabricated by anodic oxidation of aluminium. The membranes were thereafter characterized in terms of pore size distribution and chemical composition. To evaluate acute inflammatory response, the membranes were implanted in the peritoneal cavity of mice. Cell recruitment to the implant site was determined by fluorescence activated cell sorting (FACS) analysis. Cell adhesion to material surfaces was studied in terms of cell number, type, and morphology using scanning electron microscopy (SEM) and immunocytochemical staining followed by fluorescence microscopy. The fabricated nanoporous alumina membranes were found to have narrow pore size distribution. The in vivo study showed that 200 nm alumina membranes induced stronger inflammatory response than 20 nm membranes. This was reflected by the number of implant-associated phagocytes and the number of cells recruited to the implantation site. Since both pore-size membranes possess similar chemical composition, we believe that the observed difference in cell recruitment and adhesion is an effect of the material nanotopography. Our results suggest that nanotopography can be used to subtly control the recruitment and adherence of phagocytic cells during the acute inflammatory response to alumina membranes.     

纳米孔玻态炭的成孔机理与“壳芯”结构

研制的纳米孔玻态炭电极,整体呈纳米开孔结构,电容特性优良,全面超过了中孔碳气凝胶．其成孔机理研究表明：通过添加适量的固化剂-六次甲基四胺,经球磨固混后,调节固化温度,造成固化树脂颗粒内芯与外壳的交联度不同,形成“壳芯”结构;粉碎压制时,内芯作为外壳的粘合剂使材料成型,炭化时壳层不融化而阻挡内芯熔并成玻态炭．于是,碳粒内外形成丰富的开放孔隙,活化剂气体能够扩散渗入体相进行活化而得纳米孔玻态炭．