Conductivity and catalytic properties

Particularly attractive for numerous bioanalytical applications are colloidal metal (e.g., gold) and semiconductor quantum dot nanoparticles. The conductivity and catalytic properties of such systems have been employed for developing electrochemical gas sensors, electrochemical sensors based on molecular- or polymer-functionalized nanoparticle sensing interfaces, and for the construction of different biosensors including enzyme-based electrodes, immunosensors, and DNA sensors. Advances in the application of molecular and biomolecular functionalized metal, semiconductor, and magnetic particles for electroanalytical and bio-electroanalytical applications have been reviewed by Katz et al. [142]. 

Let us emphasize again that this correlation does not pretend to establish a proportionality between semiconductivity and catalytic activity. It shows however that certain changes in electronic structure of a solid which can be brought about by selected impurities are reflected upon both the conducting and catalytic properties of a solid. A deeper analysis is required if the direction of, or the change in, catalytic activity is to be predicted on a rational basis. In the last analysis these changes... 

CONDUCTIVITY AND CATALYTIC PROPERTIES OF THE LANTHANIDE HIGHER OXIDES... 

Electrical conductivity and catalytic properties of R-mixed oxides" 1 ... 

The perovskites Lai xMxB 03.5 (M = Sr, B = Co, Cr, Fe, Mn) have been reviewed by Alcock et al. in terms of their stability in temperature and oxygen partial pressiue of operation as active sensor material, nonstoiehiometry, conductivity, and catalytic properties, and the effect of the strontium eontent, x. 

Noble metal nanoparticles dispersed in insulating matrices have attracted the interest of many researchers fromboth applied and theoretical points of view [34]. The incorporation of metallic nanoparticles into easily processable polymer matrices offers a pathway for better exploitation of their characteristic optical, electronic and catalytic properties. On the other hand, the host polymers can influence the growth and spatial arrangement of the nanoparticles during the in situ synthesis, which makes them convenient templates for the preparation of nanoparticles of different morphologies. Furthermore, by selecting the polymer with certain favorable properties such as biocompatibiHty [35], conductivity [36] or photoluminescence [37], it is possible to obtain the nanocomposite materials for various technological purposes. 

Abstract In this chapter, recent progress in the synthesis, crystal structures and physical properties of monomeric phthalocyanines (Pcs) is summarized and analysed. The strategies for synthesis and modification of Pcs include axial coordination of central metal ions, peripheral substitution of Pc rings and the ionization of Pcs. The crystal structures of various typical Pcs, especially the effects of different synthetic and modification strategies on the supramolecular assemblies of Pcs via %—% interactions between Pc rings, are discussed in detail. Finally, the UV-vis spectroscopic, conducting, magnetic and catalytic properties of some Pcs with crystal structures are presented briefly, and the correlations between various properties and the molecular structure discussed. 

Annenkova et al. (105) studied both the physicochemical and catalytic properties of the Bi-Fe-Mo oxide system. The X-ray diffraction, infrared spectroscopic, and thermographic measurements indicated that the catalysts were heterogeneous mixtures consisting principally of ferric molybdate, a-bismuth molybdate, and minor amounts of bismuth ferrite and molybdenum trioxide. The Bi-Fe-Mo oxide catalysts were more active in the oxidation of butene to butadiene and carbon dioxide than the bismuth molybdate catalysts. The addition of ferric oxide to bismuth molybdate was also found to increase the electrical conductivity of the catalyst. 

We measured the electrical conductivity of Pt-C nanocomposites using two-point measurements. In a representative example the NP-polymer hybrid had a conductivity of 2.5 mS cm-1, which increased to 400 S cm-1 upon pyrolysis. Despite the presence of carbon, to the best of our knowledge this value represented the highest electrical conductivity yet measured for ordered mesoporous materials derived from block copolymers. This discovery creates a potential pathway to a new class of ordered mesoporous metals made from nanoparticles of different elements and/or distinct compositions. Such nano-heterogeneous mesoporous metals may have a range of exceptional electrical, optical, and catalytic properties. 

Several methods have been used to produce different types of OL-1, OMS-1, and OMS-2 materials. The materials that are produced by various methods lead to vastly different materials, that have unique chemical and physical properties. Some of the properties that can be controlled are particle size, color, morphology, average manganese oxidation state, thermal stability, ion-exchange capacity, electrical conductivity, magnetic properties, crystallinity, defect density, desorption of oxygen, and catalytic properties. Table IV summarizes 16 different classes of OMS-1, OMS-2, OL-1, and amorphous manganese oxide (AMO) materials that we have prepared. These materials are separated into different classes because they show different crystalline, chemical and physical properties. For the case of OMS-1 these materials... 

Electron behavior, optical properties, catalytic properties, conductivity, and magnetic properties of nanocomposites were discussed in an extensive review pa-per. Complementary use of electron paramagnetic resonance and nuclear magnetic resonance helped to understand chain mobility in nanocomposites obtained from poly(ethylene oxide) encapped with triethoxy silicon. This nanocomposite is composed of PEO chains attached to silica clusters. It was found that chain fragments close to the silica clusters have hindered mobility due to the reduction of local free volume. The length of this hindered segment is estimated as three ethylene oxide units. 

In the context of porous hybrid materials, one can note that preparation of composites of inorganic materials with conducting organic polymers is currently under intensive research in order to combine catalytic properties of inorganic materials with conductivity and redox properties of such polymers. 

Solid phosphates show a huge variety of crystal structures, and it is not practical to classify them in terms of structural types as is done with simple oxides, halides, etc. However, some general classes of metal phosphate structures will be considered three-dimensional frameworks of linked phosphate tetrahedra and tetrahedrally or octahedrally coordinated cations, layered phosphates, and phosphate glasses. In all of these materials the size and topology of pores within the structure are of importance, as these determine the ability of ions and molecules to move within the structure, giving rise to useful ion exchange, ionic conduction, or catalytic properties. Ion exchange can also be used to modify the properties of the host network, for example, the nonlinear optical behavior of potassium titanyl phosphate (KTP) derivatives. 

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