Visible-to-UV Photon Upconversion in Nanostructured Chromophoric Ionic Liquids

Shota Hisamitsu; Junji Miyano; Keisuke Okumura; Joseph Ka-Ho Hui; Nobuhiro Yanai; Nobuo Kimizuka

doi:10.1002/open.201900304

Visible-to-UV Photon Upconversion in Nanostructured Chromophoric Ionic Liquids

ChemistryOpen. 2019 Nov 26;9(1):14-17. doi: 10.1002/open.201900304. eCollection 2020 Jan.

Authors

Shota Hisamitsu¹, Junji Miyano¹, Keisuke Okumura¹, Joseph Ka-Ho Hui¹, Nobuhiro Yanai^{1

2}, Nobuo Kimizuka¹

Affiliations

¹ 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.
² JST-PRESTO, Honcho 4-1-8, Kawaguchi, Saitama, 332-0012, Japan.

Abstract

Visible-to-ultraviolet (vis-to-UV) triplet-triplet annihilation based photon upconversion (TTA-UC) is achieved in a non-volatile chromophoric ionic liquid (IL) for the first time. A novel IL is synthesized by combining UV-emitting anion 4-(2-phenyloxazol-5-yl)benzenesulfonate (PPOS) and trihexyltetradecylphosphonium cation (P₆₆₆₁₄). The nanostructured organization of chromophoric anions is demonstrated by synchrotron X-ray and optical measurements. When the IL is doped with a triplet sensitizer tris(2-phenylpyridinato)iridium(III) (Ir(ppy)₃), the visible-to-UV TTA-UC with a relatively low threshold excitation intensity of 61 mW cm^-2 is achieved. This is due to a large triplet diffusion coefficient in the IL (1.4×10^-7 cm² s^-1) as well as a high absorption coefficient 15 cm^-1 and a long PPOS triplet lifetime of 1.55 ms, all implemented in the condensed IL system. This work demonstrates the unique potential of ILs to control chromophore arrangements for desired functions.

Keywords: functional supramolecular chemistry; ionic liquids; nanostructures; photon upconversion; self-assembly.

Publication types

Research Support, Non-U.S. Gov't