title: Solvent effects on the triplet-triplet annihilation upconversion of diiodo-Bodipy and perylene.
abstract: Solvent effects play a very important role in photochemical reactions and energy transfer processes in solution; however, these effects are rarely mentioned in the triplet-triplet annihilation (TTA) upconversion fluorescence experiments. In a typical TTA upconversion system of a photosensitizer of diiodo-Bodipy (I2-Bodipy) and a triplet acceptor of perylene, five common inert solvents, hexane, heptane, toluene, 1,4-dioxane, and dimethyl sulfoxide (DMSO), were used to investigate the solvent effects on the overall quantum yield of upconversion fluorescence. Femtosecond and nanosecond time-resolved transient difference absorption spectra were obtained to study the efficiencies of intersystem crossing (ISC) and triplet-triplet energy transfer (TTET). From the obtained upconversion fluorescence emission spectra, the overall TTA upconversion fluorescence quantum yield was derived. Among the five solvents, the upconversion quantum yield in dioxane is the highest at 19.16%, more than twice that that in toluene (8.75%). For the solvents hexane, heptane, toluene, and dioxane, the yields generally follow the sequences of polarity and viscosity. However, a very low upconversion quantum yield (1.51%) was observed in DMSO although the TTET process and fluorescence quantum yield of perylene in DMSO were almost as efficient as in dioxane. Based on density functional theory calculations, a reasonable explanation for these solvent effects was proposed.
authors.affiliation: Hefei National Laboratory for Physical Sciences at the Microscale and Department of Chemical Physics, University of Science and Technology of China, Hefei, Anhui 230026, China. xzhou@ustc.edu.cn.
authors.forename: Qiaohui
authors.initials: Q
authors.lastname: Zhou
authors.affiliation: State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China. zhangsong@wipm.ac.cn.
authors.forename: Miaomiao
authors.initials: M
authors.lastname: Zhou
authors.affiliation: Hefei National Laboratory for Physical Sciences at the Microscale and Department of Chemical Physics, University of Science and Technology of China, Hefei, Anhui 230026, China. xzhou@ustc.edu.cn.
authors.forename: Yaxiong
authors.initials: Y
authors.lastname: Wei
authors.affiliation: Hefei National Laboratory for Physical Sciences at the Microscale and Department of Chemical Physics, University of Science and Technology of China, Hefei, Anhui 230026, China. xzhou@ustc.edu.cn and Synergetic Innovation Center of Quantum Information & Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.
authors.forename: Xiaoguo
authors.identifier: http://orcid.org/0000-0002-0264-0146
authors.initials: X
authors.lastname: Zhou
authors.affiliation: Hefei National Laboratory for Physical Sciences at the Microscale and Department of Chemical Physics, University of Science and Technology of China, Hefei, Anhui 230026, China. xzhou@ustc.edu.cn and Synergetic Innovation Center of Quantum Information & Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China.
authors.forename: Shilin
authors.initials: S
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China. zhangsong@wipm.ac.cn.
authors.forename: Song
authors.initials: S
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China. zhangsong@wipm.ac.cn.
authors.forename: Bing
authors.initials: B
authors.lastname: Zhang