title: All-or-none switching of photon upconversion in self-assembled organogel systems.
abstract: Aggregation-induced photon upconversion (iPUC) based on a triplet-triplet annihilation (TTA) process is successfully developed via controlled self-assembly of donor-acceptor pairs in organogel nanoassemblies. Although segregation of donor from acceptor assemblies has been an outstanding problem in TTA-based UC and iPUC, we resolved this issue by modifying both the triplet donor and aggregation induced emission (AIE)-type acceptor with glutamate-based self-assembling moieties. These donors and acceptors co-assemble to form organogels without segregation. Interestingly, these donor-acceptor binary gels show upconversion at room temperature but the upconversion phenomena were lost upon dissolution of the gels on heating. The observed changes in TTA-UC emission were thermally reversible, reflecting the controlled assembly/disassembly of the binary molecular systems. The observed on/off ratio of UC emission was much higher than that of the aggregation-induced fluorescence of the acceptor, which highlights the important role of iPUC, i.e., multi-exciton TTA for photoluminescence switching. This work bridges iPUC and supramolecular chemistry and provides a new strategy for designing stimuli-responsive upconversion systems.
authors.affiliation: Department of Chemistry and Biochemistry, Graduate School of Engineering, Center for Molecular Systems (CMS), Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395, Japan. yanai@mail.cstm.kyushu-u.ac.jp n-kimi@mail.cstm.kyushu-u.ac.jp and Key Laboratory of Nanosystem and Hierarchical Fabrication, CAS Center for Excellence in Nanoscience, National Center for Nanoscience and Technology (NCNST), No. 11 ZhongGuanCun BeiYiTiao, 100190 Beijing, P.R. China.
authors.forename: Pengfei
authors.initials: P
authors.lastname: Duan
authors.affiliation: Department of Chemistry and Biochemistry, Graduate School of Engineering, Center for Molecular Systems (CMS), Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395, Japan. yanai@mail.cstm.kyushu-u.ac.jp n-kimi@mail.cstm.kyushu-u.ac.jp.
authors.forename: Deepak
authors.initials: D
authors.lastname: Asthana
authors.affiliation: Graduate School of Materials Science, Nara Institute of Science and Technology (NAIST), 8916-5 Takayama, Ikoma, Nara 630-0192, Japan.
authors.forename: Takuya
authors.initials: T
authors.lastname: Nakashima
authors.affiliation: Graduate School of Materials Science, Nara Institute of Science and Technology (NAIST), 8916-5 Takayama, Ikoma, Nara 630-0192, Japan.
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Kawai
authors.affiliation: Department of Chemistry and Biochemistry, Graduate School of Engineering, Center for Molecular Systems (CMS), Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395, Japan. yanai@mail.cstm.kyushu-u.ac.jp n-kimi@mail.cstm.kyushu-u.ac.jp and PRESTO, JST, Honcho 4-1-8, Kawaguchi, Saitama 332-0012, Japan.
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Yanai
authors.affiliation: Department of Chemistry and Biochemistry, Graduate School of Engineering, Center for Molecular Systems (CMS), Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395, Japan. yanai@mail.cstm.kyushu-u.ac.jp n-kimi@mail.cstm.kyushu-u.ac.jp.
authors.forename: Nobuo
authors.initials: N
authors.lastname: Kimizuka