Carrier concentration dependence and impurity effects of microwave response in Bi2Sr2CaCu2O8+ y

We report the surface impedance (Z _s ) measurements in high quality single crystals of Bi₂Sr₂CaCu₂O_8+y . At relatively low oxygen content, the change of the penetration depth, Δλ(T) ≡λ(T)-λ(0), of the pure single crystals exhibits linear temperature dependence both parallel to the CuO₂ planes and in thec direction. In contrast to this behavior, by further oxygenation or 0.6% Zn substitution, theT-linear dependence is disrupted andT ² dependence of Δλ is observed. We also found that 0.9% Ni-substitution induces no pairbreaking effect. The present results suggest that the low-lying excitation spectrum of quasiparticles depends on the carrier concentration and is easily changed by a small amount of Zn substitution.     

Photoinduced Charge Separation in an Aqueous Phase Using Nanoporous TiO2 Film and a Quasi‐Solid Made of Natural Products

Solar cells comprised of nanoparticulate TiO₂ porous film photosensitized with an adsorbing dye have been utilized as photoinduced charge separation systems in aqueous media with the view to forming future artificial photosynthetic systems able to create fuels from solar energy and water. The photoinduced charge separation of the sensitized TiO₂ cell in a quasi‐solid, made from agarose or κ‐carrageenan, was investigated.

I–V curves under 98 mW · cm⁻² irradiation of ITO/TiO₂/Ru(dcbpy)₂(NCS)₂. Electrolyte: 0.1 M LiI/0.01 M I₂ in a quasi‐solid of 0.2 wt.‐% gelatin containing a large excess of water.