title: Fluorescence quenching of coumarin 153 by hydroxyl-functionalized room temperature ionic liquids.
abstract: Steady-state absorption and fluorescence as well as time-resolved fluorescence of coumarin 151 (C151) and coumarin 153 (C153) were measured in hydroxyl-functionalized ionic liquids ([HOEmim][BF4] and [HOEmim][N(CN)2]) and in nonhydroxyl-functionalized ionic liquids ([Emim][BF4] and [Emim][N(CN)2]). Both the steady-state fluorescence and time-resolved fluorescence observations reveal that hydroxyl-functionalized ionic liquid quenches the fluorescence of C153 while the nonhydroxyl-functionalized ionic liquid does not. We also measured the time-resolved fluorescence anisotropy of C151 and C153 in both [HOEmim][BF4] and [Emim][BF4]. It is found that the ratio of the rotational relaxation lifetime of C153 in [HOEmim][BF4] with respect to that in [Emim][BF4] is about 15% larger than that of C151 in [HOEmim][BF4] with respect to that in [Emim][BF4], indicating extra interaction between C153 and [HOEmim][BF4] exists except the effect of the viscosity of ionic liquid.
authors.affiliation: Department of Chemistry, Renmin University of China, Beijing, 100872, PR China.
authors.forename: Shuang
authors.initials: S
authors.lastname: Li
authors.affiliation: Department of Chemistry, Renmin University of China, Beijing, 100872, PR China. Electronic address: a.yu@chem.ruc.edu.cn.
authors.forename: Anchi
authors.initials: A
authors.lastname: Yu
authors.affiliation: Department of Chemistry, Renmin University of China, Beijing, 100872, PR China. Electronic address: lurong@ruc.edu.cn.
authors.forename: Rong
authors.initials: R
authors.lastname: Lu
keywords: Coumarin 153; Fluorescence quenching; Hydrogen bonding; Hydroxyl-functionalized ionic liquid; Time-resolved fluorescence anisotropy