Chemical and electronic properties

The chemical and electronic properties of elements at the interfaces between very thin films and bulk substrates are important in several technological areas, particularly microelectronics, sensors, catalysis, metal protection, and solar cells. To study conditions at an interface, depth profiling by ion bombardment is inadvisable, because both composition and chemical state can be altered by interaction with energetic positive ions. The normal procedure is, therefore, to start with a clean or other well-characterized substrate and deposit the thin film on to it slowly at a chosen temperature while XPS is used to monitor the composition and chemical state by recording selected characteristic spectra. The procedure continues until no further spectral changes occur, as a function of film thickness, of time elapsed since deposition, or of changes in substrate temperature. 

In addition to the establishment and understanding of activity trends on nanosegregated surfaces, it has been anticipated that finding relationships between chemical and electronic properties of thin metal films of Pt group metals deposited over 3d and 5d elements has the potential to open up new opportunities in the quest to... 

In conjunction with latest progress in quantum chemistry the availability of vast experimental data makes it possible to anal)rze the character of possible centers of adsorption of particles of various gases as well as type, chemical and electron properties of surface compounds formed during interaction of adsorption particles with adsorption centers. 

In band theory the electrons responsible for conduction are not linked to any particular atom. They can move easily throughout the crystal and are said to be free or very nearly so. The wave functions of these electrons are considered to extend throughout the whole of the crystal and are delocalized. The outer electrons in a solid, that is, the electrons that are of greatest importance from the point of view of both chemical and electronic properties, occupy bands of allowed energies. Between these bands are regions that cannot be occupied, called band gaps. 

Previous studies in conventional reactor setups at Philip Morris USA have demonstrated the significant effectiveness of nanoparticle iron oxide on the oxidation of carbon monoxide when compared to the conventional, micron-sized iron oxide, " as well as its effect on the combustion and pyrolysis of biomass and biomass model compounds.These effects are derived from a higher reactivity of nanoparticles that are attributed to a higher BET surface area as well as the coordination of unsaturated sites on the surfaces. The chemical and electronic properties of nanoparticle iron oxide could also contribute to its higher reactivity. In this work, we present the possibility of using nanoparticle iron oxide as a catalyst for the decomposition of phenolic compounds. 

One possible conclusion is that under reducing conditions, metal cation movement occurs. Another possible conclusion is that despite the similar surface layer composition of bismuth and molybdenum for the three phases of bismuth molybdate, the three bismuth molybdate phases possess different catalytic activities, catalytic selectivities, adsorption properties, surface oxomolybdenum species, and reducibilities because the surface properties of the active bismuth molybdates are dependent upon the foundation upon which they exist, i.e., upon the bulk structure and its chemical and electronic properties. 

ZnO films can provide substantial information on chemical and electronic properties of ZnO surfaces and interfaces, which occur in real thin film solar cell structures. In addition, general information on the interface formation of oxide materials can be extracted. In the following we describe ... 

Most of the heterogeneous catalyst which are in practical use consist of one or more catalytically active compounds which are impregnated on supporting carrier materials. This method can be chosen to immobilise acids and bases as well as salts, oxides or complexes. The major drawback is leaching of one or more component which leads to irreversible deactivation of the catalyst. Physisorption can be enhanced by choosing the appropriate porous, chemical and electronical properties. This leads to catalysts with sufficient long term stability due to e.g. ionic linkages. 

As originally observed by Hertz and later explained by Einstein, electron emission occurs when photons with energy greater than a material s work function irradiate it. The application of this phenomenon led to the development of photoelectron spectroscopy (PES), which is one of the principal methods used to understand chemical and electronic properties of materials. Over the last 40 years advances in technology have also made it possible to determine the spin of the electron and advances in this area have been summarized in several books and reviews [24-28]. A detailed discussion of spin-resolved PES is beyond the scope of this review. The following presents the rudimentary concepts and some illustrative examples. 

A discerning activity test in a well designed microreactor must be an integral part of the overall approach to develop the means for correlating physical, chemical and electronic properties of the catalyst with activity, selectivity and stability. 

Effect of Cluster Size on Chemical and Electronic Properties... 

What are transition metal clusters and why are they interesting For example what are the properties of a 5-atom platinum cluster Is it similar to bulk platinum or does it behave more like the atom What we are discovering is that below a certain size each small n-atom duster has unique chemical and electronic properties, it behaves neither iike the atom, the bulk, nor even 1i ke other clusters of the same metal. Thus there are opportunities to exploit their novel properties by making it possible to create new materials with potential applications in such diverse areas as solid state physics, electronics, chemistry and catalysis. 

Campbell CT, Rodriguez JA, Goodman DW (1992) Chemical and electronic properties of ultrathin metal films the PdZRe(OOOl) and Pd/Ru(0001) systems. Phys Rev B 46 7077... 

Beyond the motivation to fabricate working systems from functionalized porous silicon, there is also more fundamental interest in the reactions of its surfaces. Because the vast surface of nanocrystalline silicon contains a large fraction of the total atoms, the composition and environment of the silicon interface are believed to affect greatly the physical, chemical, and electronic properties of the material. In particular, functionalization of porous silicon with certain organic groups is known to diminish photoluminescence [27] however, the mechanism of quenching has... 

Investigations of molecular redox films are of fundamental importance to numerous technologies. Scanning probe microscopy, in combination with electrochemistry, is uniquely suited to provide invaluable information concerning the potential-dependent structural, chemical, and electronic properties on these systems. 

The introduction of sulfur into the polyanionic frameworks is expected to modify the chemical and electronic properties of the oxo-parents, and owing to the softness of sulfur new architectures are expected to be derived from the various precursors. Three different ways have been developed in our group to prepare the first polyoxothiometalates ... 

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