No abstract

We studied the effects of adsorbed water molecules on light harvesting and electron injection processes in nanocrystalline TiO2 films sensitized with Ru-complex dyes. We found that the absorption spectra of adsorbed dyes containing SCN groups were sensitive to humidity (that is, the dyes exhibited vapochromism) and that the absorption spectra of dyes adsorbed on nanocrystalline films differed slightly from the spectra of the same dyes adsorbed on TiO2 single crystals, suggesting that the orientation of the dye molecules on the surface was affected by surface-adsorbed water molecules. The dynamics of electron injection from the excited dye molecules into the TiO2 were studied by transient absorption spectroscopy. Transient absorption signal intensities decreased with decreasing humidity, indicating that electron injection efficiency was reduced by loss of water molecules from the surface. IR spectroscopy indicated that only a small amount of physisorbed water was lost upon drying, and the use of an indicator dye showed that the proton concentration around the dye molecules on the surface was markedly increased by drying. On the basis of these findings, we discuss possible mechanisms for the vapochromism and for the reduction in electron injection efficiency caused by the loss of water molecules from the surface.

No abstract

In order to create more flexible and robust soft actuators, organic/inorganic hybrid actuating fibers were prepared by coating gold fibers in polypyrrole using electropolymerization. The linear, coiled, and helical hybrid fibers were prepared by deforming gold fibers in advance. The obtained fibers exhibit various actuating motions, such as bending, stretching, and rotating motions, due to shrinking and expanding of polypyrrole by doping and de-doping of lithium cations. Merit of the actuating fibers prepared in this research is that the fibers are thin and can be easily combined. Hence, the actuating forces of the fibers caused by doping and de-doping can be amplified by combining the fibers. As a result, heavier weights could be lifted, proportional to the number of fibers combined.