title: Color-Tunable Resonant Photoluminescence and Cavity-Mediated Multistep Energy Transfer Cascade.
abstract: Color-tunable resonant photoluminescence (PL) was attained from polystyrene microspheres doped with a single polymorphic fluorescent dye, boron-dipyrrin (BODIPY) 1. The color of the resonant PL depends on the assembling morphology of 1 in the microspheres, which can be selectively controlled from green to red by the initial concentration of 1 in the preparation process of the microspheres. Studies on intersphere PL propagation with multicoupled microspheres, prepared by micromanipulation technique, revealed that multistep photon transfer takes place through the microspheres, accompanying energy transfer cascade with stepwise PL color change. The intersphere energy transfer cascade is direction selective, where energy donor-to-acceptor down conversion direction is only allowed. Such cavity-mediated long-distance and multistep energy transfer will be advantageous for polymer photonics device application.
authors.affiliation: Division of Materials Science, Faculty of Pure and Applied Sciences, University of Tsukuba , 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573, Japan.
authors.forename: Daichi
authors.initials: D
authors.lastname: Okada
authors.affiliation: Division of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba , 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8571, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Nakamura
authors.affiliation: Faculty of Physics and CENIDE, University of Duisburg-Essen , Lotharstrasse 1, Duisburg D-47048, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Braam
authors.affiliation: International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science (NIMS) , 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan.|CREST, Japan Science and Technology Agency (JST) , 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan.
authors.forename: Thang Duy
authors.initials: TD
authors.lastname: Dao
authors.affiliation: International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science (NIMS) , 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan.|CREST, Japan Science and Technology Agency (JST) , 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Ishii
authors.affiliation: International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science (NIMS) , 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan.|CREST, Japan Science and Technology Agency (JST) , 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan.
authors.forename: Tadaaki
authors.initials: T
authors.lastname: Nagao
authors.affiliation: Faculty of Physics and CENIDE, University of Duisburg-Essen , Lotharstrasse 1, Duisburg D-47048, Germany.
authors.forename: Axel
authors.initials: A
authors.lastname: Lorke
authors.affiliation: Division of Chemistry, Faculty of Pure and Applied Sciences, University of Tsukuba , 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8571, Japan.|Tsukuba Research Center for Interdisciplinary Materials Science (TIMS), Faculty of Pure and Applied Sciences, University of Tsukuba , 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8571, Japan.|Center for Integrated Research in Fundamental Science and Technology (CiRfSE), University of Tsukuba , 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8571, Japan.
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Nabeshima
authors.affiliation: Division of Materials Science, Faculty of Pure and Applied Sciences, University of Tsukuba , 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573, Japan.|Tsukuba Research Center for Interdisciplinary Materials Science (TIMS), Faculty of Pure and Applied Sciences, University of Tsukuba , 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8571, Japan.|Center for Integrated Research in Fundamental Science and Technology (CiRfSE), University of Tsukuba , 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8571, Japan.
authors.forename: Yohei
authors.initials: Y
authors.lastname: Yamamoto
keywords: BODIPY; energy transfer; microsphere; photoluminescence; whispering gallery mode