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<p>The stability of diradical-featured organic materials is one of the most challenging obstacles for potential photothermal applications because the high electrophilicity of radicals makes them short-lived and unstable. Currently, easily accessible and highly stable open-shell diradicals photothermal materials with excellent chemical/thermal/photostability are drawing increasing interest. Herein, four donor-acceptor-donor (D-A-D) featured diradicaloids, termed <b>TPA-H, TPA-BF2, Ph-TPA-H</b>, and <b>Ph-TPA-BF2</b> with large planar conjugated structures were designed and facilely synthesized by employing a strategy of “donor-acceptor (D-A) effect plus amplifying absorption reservoir”. The promising performances such as high absorptivity (<i>ε</i> up to 1.51×10<sup>5</sup> M<sup>−1</sup> cm<sup>−1</sup>), excellent thermal stability (<i>T</i><sub>d</sub> up to 456 °C), high photostability and ultra-stable ESR signals at harsh conditions (200 °C in air for 2 h and in boiling water for 2 h) are shown. Among them, it is noteworthy that two precursor compounds (<b>TPA-H</b> and <b>Ph-TPA-H</b>) featuring fewer synthetic steps and lower molecular weight with simplified chemical structure exhibit significant enhanced photothermal performance. Femtosecond transient absorption spectroscopy reveals that all four compounds exhibit excited-state lifetimes shorter than 40 ps, facilitating efficient photothermal conversion through non-radiative decay. In particular, <b>TPA-H</b> exhibited best photothermal conversion efficiency, reaching 259 °C under 808 nm laser irradiation (1.0 W cm<sup>−2</sup>), photo-ignition, and superior solar-driven water evaporation rate of 1.435 kg m<sup>−2</sup> h<sup>−1</sup> and evaporation efficiencies (<i>η</i>) of 98.6% under 1 sun illumination, which is one of the best pure organic photothermal materials. The multiple applications including photothermal-electric conversion (maximum voltage of 224 mV), co-production of water-electricity and seawater desalination were also investigated. Furthermore, <b>TPA-H</b> nanoparticles have also been applied in photothermal antibacterial study, achieving complete eradication of <i>Staphylococcus aureus</i> and <i>Escherichia coli</i>. This study develops a facile strategy to construct ultra-stable diradical-featured organic photothermal materials for high-performance photo-thermal-electric conversion applications.</p>

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Less is better: facilely boosting highly efficient photo-thermal-electric conversion via ultra-stable donor-acceptor singlet diradicals

  • 期刊论文

  • 发表日期：

    2026年1月28日

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  • Bihong Lai,
  • Yaohua Xiao,
  • Yiyi Zhang,
  • Jiaxing Huang,
  • Yuhang Yang,
  • Rui Jing,
  • Derong Cao,
  • Xueguang Ran,
  • Zhuoran Kuang,
  • Yuan Li,
  • Lingyun Wang

摘要

The stability of diradical-featured organic materials is one of the most challenging obstacles for potential photothermal applications because the high electrophilicity of radicals makes them short-lived and unstable. Currently, easily accessible and highly stable open-shell diradicals photothermal materials with excellent chemical/thermal/photostability are drawing increasing interest. Herein, four donor-acceptor-donor (D-A-D) featured diradicaloids, termed TPA-H, TPA-BF2, Ph-TPA-H, and Ph-TPA-BF2 with large planar conjugated structures were designed and facilely synthesized by employing a strategy of “donor-acceptor (D-A) effect plus amplifying absorption reservoir”. The promising performances such as high absorptivity (ε up to 1.51×105 M−1 cm−1), excellent thermal stability (Td up to 456 °C), high photostability and ultra-stable ESR signals at harsh conditions (200 °C in air for 2 h and in boiling water for 2 h) are shown. Among them, it is noteworthy that two precursor compounds (TPA-H and Ph-TPA-H) featuring fewer synthetic steps and lower molecular weight with simplified chemical structure exhibit significant enhanced photothermal performance. Femtosecond transient absorption spectroscopy reveals that all four compounds exhibit excited-state lifetimes shorter than 40 ps, facilitating efficient photothermal conversion through non-radiative decay. In particular, TPA-H exhibited best photothermal conversion efficiency, reaching 259 °C under 808 nm laser irradiation (1.0 W cm−2), photo-ignition, and superior solar-driven water evaporation rate of 1.435 kg m−2 h−1 and evaporation efficiencies (η) of 98.6% under 1 sun illumination, which is one of the best pure organic photothermal materials. The multiple applications including photothermal-electric conversion (maximum voltage of 224 mV), co-production of water-electricity and seawater desalination were also investigated. Furthermore, TPA-H nanoparticles have also been applied in photothermal antibacterial study, achieving complete eradication of Staphylococcus aureus and Escherichia coli. This study develops a facile strategy to construct ultra-stable diradical-featured organic photothermal materials for high-performance photo-thermal-electric conversion applications.