Excited state dynamics of 9,9'-bianthryl (BA) in 1-butyl-3-methylimidazolium ionic liquids with three different types of anions was investigated by means of femtosecond to nanosecond transient absorption (TA) spectroscopy and time-resolved fluorescence (TRF) measurements. TA spectroscopy revealed that charge transfer (CT) occurred multiexponentially in the time scale of hundreds of picoseconds while TRF measurement revealed that red-shift of the BA fluorescence peak extended into the nanosecond regime. It is concluded that an energy relaxation process slower than the CT reaction, which could be the solvation dynamics in the product state, is observed.

The temperature dependence of the fluorescence behaviors of 9,9′-bianthryl (BA) in the charge-transferred (CT) state in imidazolium ionic liquids (IL) was investigated by means of steady-state as well as timeresolved detections. At ambient and higher temperatures, the emission peak of BA in ILs shifted to longer wavelengths with decreasing temperature, which is a phenomenon commonly observed in normal polar solvents. On the other hand, the emission peak shifted toward shorter wavelengths with decreasing temperature below ca. 290 K. Time-resolved fluorescence (TRF) spectroscopy was carried out to investigate the dynamic Stokes shift, i.e., the time-dependent red-shift of the fluorescence peak. In highly viscous ILs, the time constant of the dynamic Stokes shift becomes comparable or longer than the lifetime of the CT state. In such a case, the ground state of BA is recovered before the completion of the solvation process. It is concluded that the origin of the blue-shifted emission at lower temperatures is due to the fluorescence from the unrelaxed CT state. It is confirmed that the charge separation process of BA in ILs occurs prior to the nanosecond fluorescence red-shift due to the slow solvation process in the CT state in the temperature range we have studied.

Boron suboxide (B 6 O) sintered bodies were prepared by a solid state reaction and a hot pressing method. The thermoelectric properties of B 6 O were compared with those of B 4 C. The electrical conductivity was smaller than that of B 4 C, and the Seebeck coefficient was twice as large as that of B 4 C indicating p-type conduction. The hopping conduction of electronic charge carriers was suggested from the temperature dependencies of the electrical conductivity and mobility. The thermal conductivity was greater than that of B 4 C. The thermoelectric dimensionless figure-of-merit increased with increasing temperature, and was 0.62 × 10 −3 at 1000 K. This value was almost in agreement with that of B 4 C.