Interface nanocrystalline

ReflEXAES can be used for near-surface structural analysis of a wide variety of samples for which no other technique is appropriate. As with EXAES, ReflEXAES is particularly suited for studying the local atomic structure around particular atomic species in non-crystalline environments. It is, however, also widely used for the analysis of nanocrystalline materials and for studying the initial stages of crystallization at surfaces or interfaces. ReflEXAES was first proposed by Barchewitz [4.135], and after several papers in the early nineteen-eighties [4.136, 4.168-4.170] it became an established (although rather exotic) characterization technique. Most synchrotron radiation sources now have beam-lines dedicated to ReflEXAES experiments. 

Nanotechnology has provided a novel way to enhance the electron-transfer rates between Hb and the electrode. As in the case of cyt c and Mb, nanocrystalline Ti02 film has been proposed to be a promising interface for the immobilization of Hb. GNPs are renowned for their good biocompatibility. With the help of these GNPs, Hb can exhibit a direct electron-transfer reaction without being denatured. To improve the... 

Nanocrystalline semiconductor thin film photoanodes, commonly comprised of a three dimensional network of inter-connected nanoparticles, are an active area of photoelectrochemistiy research [78-82] demonstrating novel optical and electrical properties compared with that of a bulk, thick or thin film semiconductor [79,80]. In a thin film semiconductor electrode a space charge layer (depletion layer) forms at the semiconductor-electrolyte interface charge carrier separation occurs as a result of the internal electric... 

Fig. 4.12 Diagram illustrating space charge layer formation in microcrystalline and nanocrystalline particles in equilibrium in a semiconductor-electrolyte interface. The nanoparticles are almost completely depleted of charge carriers with negligibly small band bending.

Studies of the kinetics and photoelectrochemistry of nanocrystalline composite films of CdS/Ni in aqueous sulfite [180] and thin film CdS/electrolyte interface were carried out [181]. 

DSSCs convert sunlight to electricity by a different mechanism than conventional p-n junction solar cell. Light is absorbed directly at the solid/liquid interface by a monolayer of adsorbed dye, and initial charge separation occurs without the need of exciton transport.42,43 Following the initial charge separation, electrons and holes are confined in two different chemical phases electrons in the nanocrystalline... 

The convoluted, high-surface-area interface between the Ti02 and the electrolyte solution is an essential characteristic of DSSCs [1-3,5,17,18]. The photoconversion process begins at this interface when the adsorbed dye, D, absorbs a photon and the resulting excited state, D, injects an electron, 2, into the nanocrystalline Ti02 semiconductor ... 

The existence of the surface contribution to the effective magnetostriction of nanocrystalline alloys has been confirmed theoretically in terms of the dipolar model (Szumiata et al. 1999). These authors showed that, due to the limited radius of the nanoparticles, additional magnetostrictive stresses are localised at the interfaces. The evaluation of the influence of the dipolar interaction on the magnetostriction in crystalline grains of perfect spherical shape surrounded by a magnetic environment of about 0.S nm with either crystalline or amorphous structure has been calculated. A similar method was previously used to obtain the surface and volume anisotropy (Draaisma and de Jonge 1988) and to... 

In Dr. M. Gratzel s plenary lecture at IPS-2000,103 he presented the following research topics to improve DSC. 1) Mastering the interfaces, electron transfer dynamics, control of dark current. 2) Charge transport in nanocrystalline films. 3) Panchromatic sensitizers, dye cocktail, quantum dot charge injection. 4) Light management, mixed metal oxide films, core-shell metal oxide films. 5) New... 

Recently, an IR spectroscopic characterization of CO adsorption on Au supported on nanocrystalline Ce02 was performed by Corma et al. [67, 86]. The presence of Au3 +, Au + and Au° species was indicated by their characteristic Aux-CO frequency. Furthermore, it was proposed that there was a direct correlation between the concentration of Au3 + species and catalytic activity for CO oxidation over nanocrystalline Ce02 supported Au. No correlation was found between catalytic activity and the concentration of Au + or Au°. These results can also be interpreted as showing that the junction perimeter interface between Au NPs and the Ce02 support is composed of Au3 + and acts as the reaction site, the length of which defines the catalytic activity. 

Jing, C Meng, X., Fiu, S. et al. (2005) Surface complexation of organic arsenic on nanocrystalline titanium oxide. Journal of Colloid and Interface Science, 290(1), 14-21. 

Solar cells, or photovoltaic devices, have been studied for many years [3], Most of the current work is focused on dye-sensitized nanocrystalline solar cells. These provide a technical and economically viable alternative to present-day photovoltaic devices. In contrast to conventional systems, in which the semiconductor assumes both the task of light absorption and charge carrier transport, the two functions are separated in dye-sensitized nanocrystalline solar cells [54] (cf. OPCs). Light is absorbed by the dye sensitizer, which is anchored to the surface of a wide-band-gap semiconductor. Charge separation takes place at the interface via photoinduced electron injection from the dye into the conduction band of the... 

Fig. 10.28. Model of charge carrier separation and charge transport in a nanocrystalline film. The electrolyte has contact with the individual nanocrystallites. Illumination produces an electron-hole pair in one crystallite. The hole transfers to the electrolyte and the electron traverses several crystallites before reaching the substrate. Note that the photogenerated hole always has a short distance (about the radius of the particle) to pass before reaching the semiconductor/electrolyte interface wherever the electron-hole pair is created in the nanoporous film. The probability for the electron to recombine will, however, depend on the distance between the photoexcited particle and the tin-coated oxide back-contact. (Reprinted with permission from A. Hagfeldt and Michael Gratzel, Light-Induced Redox Reactions in Nanocrystalline Systems Chem. Rev. 95 49-68, copyright 1995, American Chemical Society.)...

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