We have studied the ultrafast dynamics of forty aprotic molecular liquids by femtosecond optical heterodyne-detected Raman-induced Kerr effect spectroscopy. Some physical properties such as shear viscosity, density, and surface tension of the molecular liquids have also been measured. From the Fourier transform Kerr spectra in the frequency range of about 0–200 cm−1, we have found that the first moment of the low-frequency intermolecular vibrational spectrum is moderately correlated with the root of the value of surface tension divided by density. This fact indicates that the microscopic intermolecular interaction is related to the macroscopic physical property of intermolecular force in molecular liquids. On the other hand, a correlation between the first moment of the intermolecular vibrational spectrum and the interaction energy of two identical molecules is almost nonexistent. The difference between the two relations suggests that the many-body interaction effect takes a hand in the intermolecular vibrational dynamics in molecular liquids. We have also found that the shapes of the broad low-frequency vibrational spectra for aromatic molecular liquids show a clearer bimodal feature than those for non-aromatic molecular liquids. Picosecond Kerr transients for most of the molecular liquids are non-exponential. The slowest relaxation time is qualitatively explained by the Stokes–Einstein–Debye model.

In this study, we have investigated the heavy atom substitution effects on the ultrafast dynamics in nonaromatic cation-based ionic liquids, as well as the static physical properties such as shear viscosity, surface tension, glass transition temperature, and melting point. Phosphonium-based ionic liquids show lower shear viscosities and lower glass transition temperatures than their corresponding ammonium-based ionic liquids. We have also examined the substitution of a (2-ethoxyethoxy)ethyl group for an octyl group in ammonium and phosphonium cations and found that the (2-ethoxyethoxy)ethyl group reduces the shear viscosity and increases the surface tension. From the results of the ultrafast dynamics, including intra- and interionic vibrations and reorientational relaxation in the ammonium- and phosphonium-based ionic liquids measured by means of femtosecond optically heterodyne-detected Raman-induced Kerr spectroscopy, we have found that the first moment of low-frequency Kerr spectrum, omitting the contributions of clear intraionic vibrational modes, correlates to the square root of surface tension divided by density. This fact indicates that heavy atom substitution in ionic liquids provides a weaker interionic interaction arising from the larger ionic volume. On the other hand, the ether group in the cations gives the stronger interionic interaction but with a more flexible and/or less segregated nature in the ILs than the alkyl group.

Photodynamic therapy (PDT) utilizes photoirradiation in the presence of photosensitizers to ablate cancer cells via generation of singlet oxygen (O), but it is important to minimize concomitant injury to normal tissues. One approach for achieving this is to use activatable photosensitizers that can generate O only under specific conditions. Here, we report a novel photosensitizer that is selectively activated under hypoxia, a common condition in solid tumors. We found that introducing an azo moiety into the conjugated system of a seleno-rosamine dye effectively hinders the intersystem crossing process that leads to O generation. We show that the azo group is reductively cleaved in cells under hypoxia, enabling production of O to occur. In PDT in vitro, cells under mild hypoxia, within the range typically found in solid tumors (up to about 5% O), were selectively ablated, leaving adjacent normoxic cells intact. This simple and practical azo-based strategy should be widely applicable to design a range of activatable photosensitizers.

Fructose found in modern diets as a constituent of the disaccharide sucrose is absorbed by a well-characterized absorptive system integrating enzymatic hydrolysis of the disaccharide and transfer of the resulting two monosaccharides through the apical membrane of the epithelial cell. The increasing use of high-fructose syrups and crystalline fructose prompted new studies aimed at the determination of the absorptive capacity for free fructose in the human gut. Results indicate that the capacity for fructose absorption is small compared with that for sucrose and glucose and is much less than previously estimated. The unexpected finding that the simultaneous ingestion of glucose can prevent fructose malabsorption suggests that the pair of monosaccharides might be absorbed by the disaccharidase-related transport system as if they were the product of the enzymatic hydrolysis of sucrose. This absorptive mechanism might not be able to transport fructose when ingested without glucose.