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Niihori Y, Kosaka T, Negishi Y. Triplet-triplet annihilation-based photon upconversion using nanoparticles and nanoclusters. MATERIALS HORIZONS 2024; 11:2304-2322. [PMID: 38587491 DOI: 10.1039/d4mh00117f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/09/2024]
Abstract
The phenomenon of photon upconversion (UC), generating high-energy photons from low-energy photons, has attracted significant attention. In particular, triplet-triplet annihilation-based UC (TTA-UC) has been achieved by combining the excitation states of two types of molecules, called the sensitizer and emitter (or annihilator). With TTA-UC, it is possible to convert weak, incoherent near-infrared (NIR) light, which constitutes half of the solar radiation intensity, into ultraviolet and visible light that are suitable for the operation of light-responsive functional materials or devices such as solar cells and photocatalysts. Research on TTA-UC is being conducted worldwide, often employing materials with high intersystem crossing rates, such as metal porphyrins, as sensitizers. This review summarizes recent research and trends in triplet energy transfer and TTA-UC for semiconductor nanoparticles or nanocrystals with diameters in the nanometer range, also known as quantum dots, and for ligand-protected metal nanoclusters, which have even smaller well-defined sub-nanostructures. Concerning nanoparticles, transmitter ligands have been applied on the surface of the nanoparticles to efficiently transfer triplet excitons formed inside the nanoparticles to emitters. Applications are expanding to solid-state UC devices that convert NIR light to visible light. Additionally, there is active research in the development of sensitizers using more cost-effective and environmentally friendly elements. Regarding metal nanoclusters, methods have been established for the evaluation of excited states, deepening the understanding of luminescent properties and excited relaxation processes.
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Affiliation(s)
- Yoshiki Niihori
- Research Institute for Science and Technology, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan.
| | - Taiga Kosaka
- Graduate School of Science, Department of Chemistry, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan
| | - Yuichi Negishi
- Research Institute for Science and Technology, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan.
- Graduate School of Science, Department of Chemistry, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan
- Department of Applied Chemistry, Faculty of Science, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan
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Arima D, Hidaka S, Yokomori S, Niihori Y, Negishi Y, Oyaizu R, Yoshinami T, Kobayashi K, Mitsui M. Triplet-Mediator Ligand-Protected Metal Nanocluster Sensitizers for Photon Upconversion. J Am Chem Soc 2024. [PMID: 38738855 DOI: 10.1021/jacs.4c03635] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/14/2024]
Abstract
Triplet-triplet annihilation photon upconversion (TTA-UC) is attracting a great deal of attention as a viable approach to exploit unutilized wavelengths of light in solar-driven devices. Recently, ligand-protected metal nanoclusters have emerged as a compelling platform for serving as triplet sensitizers for TTA-UC. In this study, we developed an atomically precise, triplet-mediator ligand (TL)-protected metal nanocluster, Au2Cu6(S-Adm)6[P(DPA)3]2 (Au2Cu6DPA; S-Adm = 1-adamanthanethiolate, DPA = 9,10-diphenylanthracene). In Au2Cu6DPA, the excitation of the Au2Cu6 core rapidly generates a metal-to-ligand charge transfer state, followed by the formation of the long-lived triplet state (approximately 150 μs) at a DPA site in the TL. By combining Au2Cu6DPA with a DPA annihilator, we achieved a red-to-blue upconversion quantum yield (ΦUCg) of 20.7 ± 0.4% (50% max.) with a low threshold excitation intensity of 36 mW cm-2 at 640 nm. This quantum yield almost reaches the maximum limit achievable using a DPA annihilator and establishes a record-setting value, outperforming previously reported nanocrystal and nanocluster sensitizers. Furthermore, strong upconversion emission based on a pseudo-first-order TTA process was observed under 1 sun illumination, indicating that the Au2Cu6DPA sensitizer holds promise for applications in solar-energy-based systems.
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Affiliation(s)
- Daichi Arima
- Department of Chemistry, College of Science, Rikkyo University, 3-34-1, Nishiikebuku road, Toshima-ku, Tokyo 171-8501, Japan
| | - Shion Hidaka
- Department of Chemistry, College of Science, Rikkyo University, 3-34-1, Nishiikebuku road, Toshima-ku, Tokyo 171-8501, Japan
| | - So Yokomori
- Department of Chemistry, College of Science, Rikkyo University, 3-34-1, Nishiikebuku road, Toshima-ku, Tokyo 171-8501, Japan
| | - Yoshiki Niihori
- Department of Applied Chemistry, Faculty of Science, Tokyo University of Science, Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan
| | - Yuichi Negishi
- Department of Applied Chemistry, Faculty of Science, Tokyo University of Science, Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan
| | - Ryuichi Oyaizu
- Department of Chemistry, Faculty of Science, Shizuoka University, 836 Ohya, Suruga-ku, Shizuoka 422-8529, Japan
| | - Takumi Yoshinami
- Department of Chemistry, Faculty of Science, Shizuoka University, 836 Ohya, Suruga-ku, Shizuoka 422-8529, Japan
| | - Kenji Kobayashi
- Department of Chemistry, Faculty of Science, Shizuoka University, 836 Ohya, Suruga-ku, Shizuoka 422-8529, Japan
| | - Masaaki Mitsui
- Department of Chemistry, College of Science, Rikkyo University, 3-34-1, Nishiikebuku road, Toshima-ku, Tokyo 171-8501, Japan
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Mitsui M, Uchida A. Triplet properties and intersystem crossing mechanism of PtAg28 nanocluster sensitizers achieving low threshold and efficient photon upconversion. NANOSCALE 2024; 16:3053-3060. [PMID: 38240331 DOI: 10.1039/d3nr05992h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/09/2024]
Abstract
Ligand-protected metal nanoclusters have emerged as a promising platform for providing sensitizers for triplet-triplet annihilation upconversion (TTA-UC). Herein, we report [PtAg28(BDT)12]4- (PtAg28; BDT = 1,3-benzenedithiolate) as a sensitizer enabling TTA-UC at low excitation intensities. PtAg28 exhibits a long-lived triplet state (approximately 7 μs) generated with a 100% intersystem crossing (ISC) quantum yield. The mechanism driving this efficient ISC was unveiled with the aid of theoretical calculations. Specifically, the S1-T1 ISC reveals a small spin-orbit coupling (SOC) matrix element, attributed to their similar electron configuration. In contrast, the T2 state, which is energetically close to S1, features a hole distribution derived from the Py superatomic orbital of the icosahedral Pt@Ag12 core. This distribution enables direct SOC based on the orbital angular momentum change from the S1 state with a Pz-derived hole distribution. Consequently, the efficient ISC was rationalized by the S1 → T2 → T1 pathway. The T1 state possesses a metal core-to-surface metal charge transfer character, facilitating triplet energy transfer and conferring superior sensitization ability. Leveraging these characteristics, the combination of PtAg28 sensitizer with a 9,10-diphenylanthracene annihilator/emitter attained an extremely low UC threshold of 0.81 mW cm-2 at 532 nm excitation, along with efficient green-to-blue TTA-UC with an internal quantum yield (ΦUCg) of 12.2% (50% maximum). This results in a pseudo-first-order TTA process with strong UC emission under 1-sun conditions.
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Affiliation(s)
- Masaaki Mitsui
- Department of Chemistry, College of Science, Rikkyo University, 3-34-1, Nishiikebukuro, Toshima-ku, Tokyo 171-8501, Japan.
| | - Atsuki Uchida
- Department of Chemistry, College of Science, Rikkyo University, 3-34-1, Nishiikebukuro, Toshima-ku, Tokyo 171-8501, Japan.
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