Alumina Membranes (alumina + membrane)

Distribution by Scientific Domains


Selected Abstracts


Co-Cultures of Primary Cells on Self-Supporting Nanoporous Alumina Membranes,

ADVANCED ENGINEERING MATERIALS, Issue 7 2010
Andreas Hoess
Due to their unique properties, self-supporting nanoporous aluminum oxide (alumina) membranes are useful substrates for the indirect co-cultivation of cells. The membrane can act as a physical barrier between different cell types, whereas the cell-to-cell communication is guaranteed by the diffusion of soluble molecules or factors through the pores. With the help of such membranes the mRNA expression of hepatic genes can be induced in human adipose-derived mesenchymal stem cells (hASCs) during an indirect co-cultivation with primary mouse hepatocytes under different culture conditions. This proof of concept shows that such a cultivation approach is beneficial for different issues in the field tissue engineering or cell therapy. [source]


Nanoporous Alumina Membranes as Diffusion Controlling Systems

ADVANCED FUNCTIONAL MATERIALS, Issue 12 2004
S. Kipke
Abstract This work describes the use of nanoporous alumina membranes for the diffusion of crystal violet molecules, encapsulated in the micelles of sodium dodecylsulfate (SDS), through pores ranging between 20 and 200,nm in diameter. The encapsulation of the crystal violet in SDS micelles is necessary in order to enlarge the size of the molecules to such an extent that the pore size becomes a speed-controlling function. Superior results were obtained when the membrane-containing capsule is placed into a water-filled beaker, and carefully moved by means of a "tipping bridge" in order to prevent diffusion problems in the capsule. Free crystal violet was liberated following diffusion due to the low SDS concentration in the aqueous solution, which was far below the critical micelle concentration (CMC). Micelle formation and encapsulation of crystal violet is shown by UV-visible and fluorescence spectroscopies. The experiments described herein serve as an exploratory test for developing novel drug delivery systems. [source]


Synthesis of Nanotube Array Composed of an Amorphous Matrix Embedded with NaCl-Type SiC Crystallites by Chemical Vapor Infiltration Techniques

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2010
Wen Yang
Highly dense oriented arrays of nanotubes were synthesized via a chemical vapor infiltration process using anodic alumina membrane as a template. The nanotubes have a unique granular structure, which is composed of SiC nanocrystals embedded in an amorphous matrix. X-ray diffraction and high-resolution transmission electron microscopy examinations both indicate an NaCl-type crystalline structure of the SiC nanocrystals in the nanotubes. The process described here can be extended to the preparation of other nanomaterials that are suitable to be obtained via a vapor,solid approach. [source]


Molecular-selective adsorption property of chemically surface modified nanoporous alumina membrane by di(1-naphthyl)silanediol to anthracenes

APPLIED ORGANOMETALLIC CHEMISTRY, Issue 3 2010
Kenji Kakiage
Abstract Nano-porous alumina membrane (NPAM) formed by the anodic oxidation of aluminum is an attractive composite as the base material for a functional filter, because of its honeycombed ordered structure with large surface area per weight and also high shape stability. In this work, we investigated the adsorption properties of the NPAM possessing ,-electron systems on the surface, which were produced through chemical surface modification by di(1-naphthyl)silanediol, to aromatic compounds using anthracenes as typical aromatic compounds. The chemically surface-modified NPAM exhibited strong affinity to anthracene molecules and the affinity was observed to be weakened remarkably with the introduction of methyl and phenyl substituents to anthracene, indicating a molecular-selective adsorption property of the NPAM. Copyright 2009 John Wiley & Sons, Ltd. [source]


Template-synthesized Protein Nanotubes with Controlled Size Based on Layer-by-layer Method

CHINESE JOURNAL OF CHEMISTRY, Issue 2 2010
Caihong Tao
Abstract The protein nanotubes fabricated by a layer-by-layer deposition method using the porous alumina membrane as the template were described. The combination of the template method and the layer-by-layer assembly technique for the fabrication of protein nanotubes presented simplicity and versatility. The nanotubes composed of two kinds of proteins (bovine serum albumin and hemoglobin lyophilized bovine erythrocytes) with different sizes could be synthesized through this method. The outside diameter of the obtained nanotubes was determined by the diameter of the pores of the template. And the wall thickness of the protein nanotubes increased with the increase of the number of protein layers that made up of the walls of nanotubes. Such biodegradable nanotubes with good biocompatibility should be useful for in vivo applications. [source]


Polydivinylbenzene/Ethylvinylbenzene Composite Membranes for the Optimization of a Whole Blood Glucose Sensor

ELECTROANALYSIS, Issue 1 2006
Kerry Bridge
Abstract A novel ultra thin polydivinylbenzene/ethylvinylbenzene composite membrane has been developed for use as the outer covering barrier in a model amperometric glucose oxidase enzyme electrode. The composite membrane was formed via the cathodic electropolymerization of divinylbenzene/ethylvinylbenzene at the surface of gold sputter coated host alumina membranes, (serving solely as a mechanical support for the thin polymer film). Permeability coefficients were determined for the enzyme substrates, O2 and glucose, across composite membranes formed with a range of polymer thicknesses. Due to the highly substrate diffusion limiting nature of the composite membrane, it was found that anionic interferents present in blood (such as ascorbate), were effectively screened from the working electrode via a charge exclusion mechanism, in a manner similar to previous findings within our laboratory. The enzyme electrode showed an initial 32% signal drift when first exposed to whole human blood over a period of 2 hours, after which time enzyme electrode responses remained essentially stable. Whole blood patient glucose determinations yielded a correlation coefficient of r2=0.97 in comparison to standard hospital analyses. [source]


Nanoporous Alumina Membranes as Diffusion Controlling Systems

ADVANCED FUNCTIONAL MATERIALS, Issue 12 2004
S. Kipke
Abstract This work describes the use of nanoporous alumina membranes for the diffusion of crystal violet molecules, encapsulated in the micelles of sodium dodecylsulfate (SDS), through pores ranging between 20 and 200,nm in diameter. The encapsulation of the crystal violet in SDS micelles is necessary in order to enlarge the size of the molecules to such an extent that the pore size becomes a speed-controlling function. Superior results were obtained when the membrane-containing capsule is placed into a water-filled beaker, and carefully moved by means of a "tipping bridge" in order to prevent diffusion problems in the capsule. Free crystal violet was liberated following diffusion due to the low SDS concentration in the aqueous solution, which was far below the critical micelle concentration (CMC). Micelle formation and encapsulation of crystal violet is shown by UV-visible and fluorescence spectroscopies. The experiments described herein serve as an exploratory test for developing novel drug delivery systems. [source]


Hydrogen separation of methyltriethoxysilane templating silica membrane

AICHE JOURNAL, Issue 12 2007
Jong-Ho Moon
Abstract Hydrogen separation on microporous methyltriethoxysilane-templating silica composite/,-alumina membranes (below MTES membrane) was studied using three binary gas mixtures: H2/N2, H2/CO2, and H2/CH4. The characteristics of unsteady and steady-state permeation/separation on the MTES membrane were compared to each other. Although permeation flux in the H2/N2 mixture was comparatively low, H2 selectivity was high (H2/N2 SF , 30,60). On the contrary, the H2/CO2 mixture showed high permeation flux but low H2 selectivity (H2/CO2 SF , 1.5,6.5). The H2/CH4 mixture showed a large difference between permselectivity (28,48) and separation factor (10,22). Results from this study revealed that it was difficult to predict the separation factor using the one-component permeation ratio (permselectivity) over the experimental range tested. These separation characteristics could be primarily ascribed to the molecular size and structure of each gas, which likely contributed to steric hindrance or molecular sieving within the membrane pore. In addition, the adsorption affinity of each molecule on the membrane surface acted as a key factor in separation performance because it significantly influenced surface diffusion. The generalized Maxwell-Stefan model incorporating the dust gas model, and the Langmuir model could successfully predict the transient and steady-state permeation/separation. 2007 American Institute of Chemical Engineers AIChE J, 2007 [source]


Nanoporous aluminum oxide affects neutrophil behaviour

MICROSCOPY RESEARCH AND TECHNIQUE, Issue 5 2004
M. Karlsson
Abstract This study evaluates neutrophil responses on aluminum oxide membranes. Using an in vitro cell culture system, we have found that the pore size (20 and 200 nm in diameter) of alumina membranes have a significant effect on leukocyte morphology and activation. Specifically, our results show that 20-nm pore-size membranes were more potent in triggering PMN spreading and extending of pseudopodia than 200-nm pore-size membranes. The morphological changes are also associated with cell activation. In fact, adherent neutrophils on 20-nm pore-size membranes elicit much stronger initial oxygen free radical production. Overall, our results point out that membrane pore size significantly affects the extent of cellular responses of adherent neutrophils. Microsc. Res. Tech. 63:259,265, 2004. 2004 Wiley-Liss, Inc. [source]


Rf glow discharge optical emission spectrometry for the analysis of arrays of Ni nanowires in nanoporous alumina and titania membranes

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 6 2006
V. M. Prida
Abstract Anodic alumina (Al2O3) and titania (TiO2) nanoporous oxide membranes are among the most widely studied self-organized nanopore templates, formed by uniform and well aligned arrays of synthetized nanometric pores or tubes. Here, we perform a comparative study of the depth profiling analysis in self-ordered alumina and titania nanoporous membrane templates by means of the radiofrequency glow discharge coupled to optical emission spectrometry (rf-GD-OES) technique. The densely packed columnar arrays of hexagonally self-ordered nanoporous alumina membranes investigated, with an average inner pore diameter of 35 nm and 105 nm interspacing, give an uniform thickness pore length about more than 5 m, depending on the anodization time. Meanwhile, the analysis of the anodized titania nanotubes, with an average inner pore diameter of 100 nm and 40 nm wall thickness, shown to be about 300 nm in length. Each type of membranes were also studied in both cases, when the nanopores were empty and after filling with electrodeposited Ni. The direct analysis by rf-GD-OES reveals the ability of this technique to control the quality of these so synthesized nanocomposites formed by electrodeposited Ni nanowires into the alumina and titania nanoporous templates. ( 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


Nanofabrication of aligned conducting polymers,

POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 9-10 2006
Muge Acik
Abstract Poly(pyrrole), poly(N-methyl pyrrole), poly(thiophene) and poly(3,4-ethylenedioxythiophene) nano-arrays, nano-fibers and nano-tubes have been successively synthesized using polycarbonate and alumina membranes as templates. Oxidative chemical polymerization method was used to produce nano-structured conducting polymers with diameters in the range of 80,350 nm and the size of the resulting polymer was controlled with the pore size of membrane. Preliminary results showed that highly oriented polymers are promising materials for many applications including supercapacitors, sensors and photonic devices. Copyright 2006 John Wiley & Sons, Ltd. [source]


Recovery of Homogeneous Polyoxometallate Catalysts from Aqueous and Organic Media by a Mesoporous Ceramic Membrane without Loss of Catalytic Activity

CHEMISTRY - A EUROPEAN JOURNAL, Issue 11 2006
Sankhanilay Roy Chowdhury Dr.
Abstract The recovery of homogeneous polyoxometallate (POM) oxidation catalysts from aqueous and non-aqueous media by a nanofiltration process using mesoporous ,-alumina membranes is reported. The recovery of Q12[WZn3(ZnW9O34)2] (Q=[MeN(n -C8H17)3]+) from toluene-based media was quantitative within experimental error, while up to 97,% of Na12[WZn3(ZnW9O34)2] could be recovered from water. The toluene-soluble POM catalyst was used repeatedly in the conversion of cyclooctene to cyclooctene oxide and separated from the product mixture after each reaction. The catalytic activity increased steadily with the number of times that the catalyst had been recycled, which was attributed to partial removal of the excess QCl that is known to have a negative influence on the catalytic activity. Differences in the permeability of the membrane for different liquid media can be attributed to viscosity differences and/or capillary condensation effects. The influence of membrane pore radius on permeability and recovery is discussed. [source]