title: Ultrafast dynamics of a solution in spatially restricted environments studied by photothermal spectroscopies.
abstract: The ultrafast dynamics of a solution in spatially restricted environments was studied by using the ultrafast transient lens (UTL) method. The UTL method is used to monitor the molecular dynamics of a solution by means of a change in the refractive index, which is advantageous for investigating the molecular dynamics of restricted systems. We investigated the photoisomerization of azobenzene derivatives in cyclodextrin nanocavities and revealed how the confinement affects the photoisomerization dynamics and yields. We also studied the relaxation dynamics of photo-excited auramine O (AuO) in a water/aerosol-OT/n-heptane reversed micelle. Both the perturbed properties of the included water and the interactions between AuO and the interface of the reversed micelle strongly appeared to affect the relaxation dynamics. At the same time, we observed a change in the refractive index suggesting a structural change of the micelles in the picosecond region that could not be detected by transient absorption spectroscopy. In addition, we developed the total internal reflection UTL (TIR-UTL) method to monitor the ultrafast molecular dynamics at the liquid interface. The relaxation dynamics of photoexcited AuO at the silica/water interface were observed with subpicosecond time resolution, and it was revealed that the interaction with the interface strongly inhibited the relaxation process. These results demonstrated the advantages of the UTL method for investigating the molecular dynamics of a solution in spatially restricted environments.
authors.affiliation: Department of Advanced Materials Science, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5-603 Kashiwanoha, Kashiwa, Chiba 277-8561, Japan. hirose@ksp.or.jp
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Hirose
authors.forename: Hiroharu
authors.initials: H
authors.lastname: Yui
authors.forename: Tsuguo
authors.initials: T
authors.lastname: Sawada
mesh_terms: D001391:Azo Compounds / Q000737:chemistry; D001576:Benzophenoneidum / Q000737:chemistry; D008823:Micelles; D015394:Molecular Structure; D012031:Refractometry; D012996:Solutions / Q000737:chemistry*; D013053:Spectrophotometry / Q000295:instrumentation / Q000379:methods
chemical_list: D001391:Azo Compounds; D008823:Micelles; D012996:Solutions; D001576:Benzophenoneidum; C009850:azobenzene