Membranes sensor materials

Reactor type Chip reactor with thin-film sensors and membrane Catalyst material Pt... 

Solid mixed ionic-electronic conductors (MIECs) exhibit both ionic and electronic (electron-hole) conductivity. Naturally, in any material there are in principle nonzero electronic and ionic conductivities (a i, a,). It is customary to limit the use of the term MIEC to those materials in which a, and 0, 1 do not differ by more than two orders of magnitude. It is also customary to use the term MIEC if a, and Ogi are not too low (o, a i 10 S/cm). Obviously, there are no strict rules. There are processes where the minority carriers play an important role despite the fact that 0,70 1 exceeds those limits and a, aj,i< 10 S/cm. In MIECs, ion transport normally occurs via interstitial sites or by hopping into a vacant site or a more complex combination based on interstitial and vacant sites, and electronic (electron/hole) conductivity occurs via delocalized states in the conduction/valence band or via localized states by a thermally assisted hopping mechanism. With respect to their properties, MIECs have found wide applications in solid oxide fuel cells, batteries, smart windows, selective membranes, sensors, catalysis, and so on. 

Crown ethers of the type discussed in this section have been used as sensors, membranes, or materials for chromatography. Shinkai used cholesterol-substituted crown ether 10 as a sensor for chirality in chiral ammonium compounds (Scheme 16). It was found that the pitch of the cholesteric phase exhibited by 10 was changed upon addition of the chiral salt. As the wavelength of reflection for incident light depends on the pitch, a color change was observed that was visible to the naked eye [45, 46]. Such chirality sensing systems were known before but chromophores had to be bound to the crown ether in order to observe color changes [47]. This problem could be overcome by 10, which uses intrinsic properties of the chiral nematic phase. 

The construction and electrochemical response characteristics of poly (vinyl chloride) membrane sensors for donepezil HC1 are described. The sensing membranes incorporate ion association complexes of donepezil HC1 cation and sodium tetraphenyl borate (sensor 1), or phospho-molybdic acid (PMA) (sensor 2), or phosphotungstic acid (sensor 3) as electroactive materials. The sensors display a fast, stable, and near-Nemstian response over a relative wide donepezil HC1 concentration... 

Fuel Cell Technology Catalytic Membrane Reactors Materials Research Chemical Sensors Electrolytic Technology Machining Welding Monopropellant Fuels... 

Another class of dense inorganic membranes that have been used in membrane reactor applications are solid oxide type membranes. These materials (solid oxide electrolytes) are also finding widespread application in the area of fuel cells and as electrochemical oxygen pumps and sensors. Due to their importance they have received significant attention and their catalytic and electrochemical applications have been widely reviewed [94-98]. Solid materials are known which conduct a variety of cationic/anionic species [14,98]. For the purposes of the application of such materials in catalytic membrane reactor applications, however, only and conducting materials are of direct relevance. 

Another key step is the proper development of surface chemistry to attach addressable probes onto different membrane sensors. This can be achieved by patterning UV-curable acrylic-based polymers inside the microfluidic channel doped with different monomers containing charged or functional groups. Such polymers are ion-selective and provide reactive chemical groups on their surfaces for the attachment of DNA/RNA probes. The functionality of aU the devices proposed here relies on the ion-selectivity of the polymeric material, which is less dependent on... 

Shahinpoor and Moj aired used ion-exchange materials and membranes to produce electrically responsive actuators [41—48] and also encapsulated ion-exchange membrane sensor/actuators. Shahinpoor used electrically responsive polymers coupled with springs and other mechanical devices to improve upon electrically responsive actuators [52] and ionic polymeric conductor composites and ionic polymer metal composites to drive pumps and mini-pumps [41]. 

Although a wide range of synthetic and natural, organic and inorganic materials showing some selectivity and ionic conductivity were described from time to time, none was widely utilized until Ross described a liquid membrane sensor for calcium in 1967. This was based... 

Buriak JM, Stewart MP, Geders TW, Allen MJ, Choi HC, Smith J, Raftery D, Canham LT (1999) Lewis acid mediated hydrosilylation on porous silicon surfaces. J Am Chem Soc 121 11491-11502 Connolly EJ, O Halloran GM, Pham HTM, Sarro PM, French PJ (2002) Comparison of porous silicon, porous polysilicon and porous silicon carbide as materials for humidity sensing applications. Sens Actuators B 99 25-30 Ftirjes P, Kovdcs A, Cs D, Addm M, Muller B, Mescheder U (2003) Porous silicon-based humidity sensor with interdigital electrodes and internal heaters. Sens Actuators B 95 140-144 Hedrich F, BiUat S, Lang W (2000) Structuring of membrane sensors using sacrificial porous silicon. Sens Actuators A 84 315-323... 

After removing chloroform, the residual uranyl salt is incorporated with mediator into PVC membranes. This simple technique has proved useful for preparing other sensor material, e.g. zinc and beryllium organophosphates. 

Successful applications of NDs in polymer nanocomposites for electronics materials [233] materials having proton conductivity [234] or enhanced thermal conductivity [235] for selective membranes, sensors, catalytic systems, nonlinear optical materials [230, 236], and elastomers of enhanced strength, wear and heat-ageing resistance [230,237,238] can all serve as examples. 

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