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Photon Upconversion with a Low Threshold Excitation Intensity in Plain Water
Yuki Nakadai1, Shuta Tsuchiya2, Masumi Uehara1
1Department of Materials Science and Technology, Faculty of Engineering, Niigata University, 8050 Ikarashi-2, Niigata950-2181, Japan.
The Journal of Physical Chemistry. B
|October 10, 2022
Summary
Researchers developed a novel photon upconversion system using triplet-triplet annihilation (TTA-UC) in plain water. This system achieves a low excitation intensity threshold, making it efficient for aqueous applications.
Area of Science:
- Photochemistry
- Materials Science
- Supramolecular Chemistry
Background:
- Photon upconversion (UC) enhances light harvesting by converting lower-energy photons to higher-energy ones.
- Triplet-triplet annihilation (TTA-UC) is a promising UC mechanism but often requires organic solvents and additives.
- Developing efficient TTA-UC systems in aqueous media is crucial for biological and environmental applications.
Purpose of the Study:
- To develop a TTA-UC system functional in plain water without surfactants.
- To achieve a low threshold excitation intensity for aqueous TTA-UC.
- To demonstrate the feasibility and efficiency of the developed aqueous TTA-UC system.
Main Methods:
- Utilized water-soluble anionic porphyrin (PdTPPS4-) as a sensitizer and a diphenylanthracene derivative (DCDPA2-) as an emitter.
- Investigated triplet energy transfer via phosphorescence quenching and fluorescence emission.
- Employed three independent emission studies with different light sources to validate the TTA-UC process.
- Measured time profiles of phosphorescence and fluorescence under pulse laser excitation to confirm TTA mechanism.
Main Results:
- Successfully demonstrated TTA-UC in a simple aqueous solution using PdTPPS4- and DCDPA2-.
- Observed efficient triplet energy transfer from PdTPPS4- to DCDPA2-, leading to DCDPA2- fluorescence emission.
- Estimated a low threshold excitation intensity (Ith) for TTA-UC, below 6 mW cm-2.
- Achieved an Ith comparable to high-performance TTA-UC systems in organic solutions, representing a new benchmark for aqueous systems.
Conclusions:
- Developed the first TTA-UC system operating efficiently in plain water without additives.
- The system exhibits a significantly low excitation intensity threshold, suitable for various aqueous applications.
- This breakthrough paves the way for advanced photon upconversion technologies in biological imaging, sensing, and photocatalysis in aqueous environments.
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