title: Single-molecule lactonization of octadecylrhodamine B at a liquid-liquid interface.
abstract: The total internal reflection laser fluorescence microscope method was used to observe the lateral diffusion of a single octadecylrhodamine B (C(18)RB) molecule at the toluene-water interface. The interfacial diffusion constant of single fluorescent cation C(18)RB(+) was obtained from the maximum residence time in a small observation area with pH <2. For pH >3, the maximum residence time was remarkably shortened, indicating that single fluorescent zwitterion C(18)RB(±) rapidly converted to the nonfluorescent lactone at the interface. The lactonization rate was completed within 0.13 ms at the toluene-water interface but slowed to 67 ms at an interface saturated with dimyristoylphosphatidylcholine.
authors.affiliation: Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Japan.
authors.forename: Tomoko
authors.initials: T
authors.lastname: Matsui
authors.forename: Satoshi
authors.initials: S
authors.lastname: Tsukahara
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Watarai
mesh_terms: D004058:Diffusion; D005453:Fluorescence; D006863:Hydrogen-Ion Concentration; D012235:Rhodamines / Q000737:chemistry*; D013499:Surface Properties; D014050:Toluene / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
chemical_list: D012235:Rhodamines; C425723:octadecylrhodamine B; D014867:Water; D014050:Toluene