Nanocrystalline surface charge

The density data are pr = 4.249 g/cm and Pa = 3.893 g/cm. Both the density data and their structure analysis of the unsatisfied surface charges associated with several exposed faces of anatase and rutile support the fact that rutile has higher surface energy than anatase. Unfortunately, direct measurements of surface energies were not available. Based on the available data, the nanocrystalline anatase-rutile system is classified as Case 3 discussed above (a-phase = anatase and P-phase = rutile in Figs. 14 and 15). 

Coordination Complexes Gerfin, T., Gratzel, M., and Walder, L., Molecular and Supramolecular Surface Modification of Nanocrystalline Ti02 Films Charge-Separating and 1 381... 

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... 

The other important aspect in dye-sensitized solar cells is water-induced desorption of the sensitizer from the TiC>2 surface. Extensive efforts have been made in our laboratory to overcome this problem by introducing hydrophobic properties in the ligands 13-17. The absorption spectra of these complexes show broad features in the visible region and display maxima around 530 nm. The performance of these hydrophobic complexes as charge transfer photosensitizers in nanocrystalline TiC>2-based solar cells shows excellent stability towards water-induced desorption [36]. 

The competition between molecular-based and molecule-substrate interactions is one of the features that make supramolecular assemblies based on the combination of molecular components and solid substrates so exciting and also potentially useful from the applications point of view. The control issue is whether can one achieve long-lived charge separation between molecular components when immobilized on a surface, and from the fundamental perspective, can the interactions between the surface and molecular components be manipulated In this section, the immobilization of molecular components consisting of at least two electroactive and/or photoactive units will be discussed. The intramolecular interactions within these dyads in solution, as well as their behavior as interfacial supramolecular triads when immobilized on nanocrystalline TiC>2, will be compared. 

The results obtained for the solar cell discussed above suggest a strong interaction between the chromophore and the metal oxide layer, a large surface area, thus yielding large absorbances, and an efficient charge-separation upon injection. Several studies have indeed been carried out in an attempt to utilize the potential of nanocrystalline metal oxides as substrates for electrochromic devices. A particularly interesting approach has been reported by Fitzmaurice and co-workers [17]. These authors have constructed an electrochromic device based on the combination of... 

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