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Visible-to-UV Photon Upconversion in Nanostructured Chromophoric Ionic Liquids
Shota Hisamitsu1, Junji Miyano1, Keisuke Okumura1
1Department of Chemistry and Biochemistry, Graduate School of Engineering, Center for Molecular Systems (CMS), Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka, 819-0395, Japan.
Chemistryopen
|January 11, 2020
Summary
Visible-to-ultraviolet photon upconversion (TTA-UC) is now possible in ionic liquids (ILs). This novel chromophoric IL system enables efficient TTA-UC, opening new possibilities for light manipulation technologies.
Area of Science:
- Materials Science
- Photochemistry
- Ionic Liquids
Background:
- Photon upconversion (UC) converts lower-energy photons to higher-energy ones.
- Triplet-triplet annihilation (TTA) is a key mechanism for UC.
- Ionic liquids (ILs) offer unique solvent properties but their use in TTA-UC is underexplored.
Purpose of the Study:
- To achieve visible-to-ultraviolet (vis-to-UV) photon upconversion using TTA in a novel ionic liquid.
- To investigate the role of IL nanostructure and properties on TTA-UC efficiency.
- To demonstrate the potential of ILs for tailored chromophore arrangement and function.
Main Methods:
- Synthesis of a novel chromophoric ionic liquid (IL) combining a UV-emitting anion (PPOS) and a phosphonium cation (P66614).
- Characterization of IL nanostructure using synchrotron X-ray and optical measurements.
- Doping the IL with a triplet sensitizer (Ir(ppy)3) to achieve TTA-UC and measuring its performance.
Main Results:
- Successful demonstration of vis-to-UV TTA-UC in a non-volatile chromophoric IL for the first time.
- Observation of nanostructured organization of chromophoric anions within the IL.
- Achieved a low threshold excitation intensity (61 mW cm⁻²) for TTA-UC due to high triplet diffusion and long PPOS triplet lifetime in the IL.
Conclusions:
- Ionic liquids can be designed to host and organize chromophores for efficient photon upconversion.
- The developed IL system exhibits favorable properties for TTA-UC, including high triplet diffusion and long chromophore triplet lifetime.
- This work highlights the potential of ILs as a versatile platform for advanced optical materials.
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