Nanoporous membrane

Immunoisolation Molecular sieves and channels Nanofiltration membranes Nanopores Separations Biological research Nanobiology... 

From a materials perspective, the field of semiconductor electrochemistry and photoelectroehemistry has evolved from the use of semiconduetor single crystals to polycrystalline thin films and, more recently, to nanocrystalline films. The latter have been variously termed membranes, nanoporous or nanophase films, meso-porous films, nanostructured films, etc. they are all distinguished from their poly-... 

The membrane nanoporous layers are proposed to be formed by laser sintering of nanopowders deposited onto the surface of microporous structure by sol-gel sedimentation/centrifugation technique. In principle, the method of laser sintering is well known [1], However, there is no wide application in practice of nanopowder processing up to date. A number of constraints defines what quality of sintered stmcture may or may not be achieved by this technique. On the whole, the comprehension of nanopowder sintering mechanisms by laser radiation is rather low. 

Another alternative to replace conventional ion exchange membranes is nanoporous silicon membrane. Nanoporous silicon membrane has been implemented in PEM fuel cells primarily due to its compatibility with microfabrication, stability at elevated temperatures, higher proton conductivity, and free from volumetric size change. As shown in Fig. 8, Moghaddam... 

Aksimentiev, A. and Schulten, K., 2004. Extending molecular modeling methodology to study insertion of membrane nanopores, Proc. Natl. Acad. Sci. USA, 101,4337 338. 

Solid-state nanopores, or nanopores comprising primarily synthetic materials, have become ubiquitous because of the ease with which material composition and pore size can be controlled. Background on the most common solid-state systems, which include nanoporous membranes, nanopores within silicon supports, nanopipettes, nanofluidic platforms, and nanoporous graphene, is considered. A direct comparison of sizes and characteristics of nanopores within these systems can be found in Table 11.1. 

A question of practical interest is the amount of electrolyte adsorbed into nanostructures and how this depends on various surface and solution parameters. The equilibrium concentration of ions inside porous structures will affect the applications, such as ion exchange resins and membranes, containment of nuclear wastes [67], and battery materials [68]. Experimental studies of electrosorption studies on a single planar electrode were reported [69]. Studies on porous structures are difficult, since most structures are ill defined with a wide distribution of pore sizes and surface charges. Only rough estimates of the average number of fixed charges and pore sizes were reported [70-73]. Molecular simulations of nonelectrolyte adsorption into nanopores were widely reported [58]. The confinement effect can lead to abnormalities of lowered critical points and compressed two-phase envelope [74]. 

FIG. 11 Schematic illustration of the electric potential profiles inside and outside a nanopore with lipid bilayer membranes separating the internal and external electrolyte solutions. The dotted line is a junction potential representation where the internal potential is shifted. 

Recently, the LbL technique has been extended from conventional nonporous substrates to macroporous substrates, such as 3DOM materials [58,59], macroporous membranes [60-63], and porous calcium carbonate microparticles [64,65], to prepare porous PE-based materials. LbL-assembly of polyelectrolytes can also be performed on the surface of MS particles preloaded with enzymes [66,67] or small molecule drugs [68], and, under appropriate solution conditions, within the pores of MS particles to generate polymer-based nanoporous spheres following removal of the silica template [69]. 

An alumina matrix may be prepared with high pore density (more than 60 %) and pore diameters ranging from 5 to 250 nm. Ruiz-Hitzky et al. [214] immobilized GOD in nanoporous alumina membranes with regular hexagonal arrays of highly ordered cylindrical pores aligned perpendicularly to the membrane surface. GOD was anchored in the membrane by the highly hydrophilic chitosan biopolymer. Full activity was maintained for at least 50 hours. 

Hatori, H., H. Takagi, and Y. Yamada, Gas separation properties of molecular sieving carbon membranes with nanopore channels, Carbon, 42, 1169-1173, 2004. 

Rao, M.B. and S. Sircar, Nanoporous carbon membranes for separation of gas mixtures by selective surface flow, /. Membr. Sci., 85(3), 253-264, 1993a. 

Figure 14.11. A non linear optical material formed from nanopores in an InP membrane. The picture on the left is the top view, whereas that on the right shows the cross section. [Reproduced with permission from Ref. 60. Copyright 2003 Wiley-VCH.]... 

Fig. 1 Nanoporous membrane from a cylinder-forming PPS-PI-PPS triblock copolymer. Reproduced from [14]...

Fig.2 TEM image (without staining) of a nanoporous PS membrane formed by ozonolysis and washing. Reproduced from [18]...

Fig. 4 Nanoporous membrane from an etched gyroid structure. Reproduced from [21]... 

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