Diradicaloid Strategy for High-Efficiency Photothermal Conversion and High-Sensitivity Detection of Near Infrared Light

Organic molecules are promising near infrared (NIR) photothermal materials because of their structural flexibility and fine-tuned properties. However, weak NIR absorption and strong fluorescence character lead to low photothermal conversion efficiency (PCE). Herein, NIR quinoidal diradicaloids are designed and synthesized by a heteroaromatic-bridged Blatter radical strategy. Benefiting from the relatively planar framework and diradical character, these singlet diradicaloids exhibit strong and broad absorption in the NIR region (750-1100 nm) in both solution and aggregate states, which do not show any fluorescence. High PCE up to 71.4% is evaluated under 808 nm laser. On this basis, a NIR detector employing a blend of the diradicaloids and conductive ionic liquid is fabricated, yielding a remarkably high thermal response of 1100% at 0.5 W cm(-2). This work reveals that pi-conjugated diradicaloids are promising candidates for NIR detection.

Automated summary

NIR quinoidal diradicaloids are designed and synthesized by a heteroaromatic-bridged Blatter radical strategy, which exhibit strong and broad absorption in the NIR region and no fluorescence. With high PCE up to 71.4% under 808 nm laser, these diradicaloids are promising candidates for NIR detection. A NIR detector employing a blend of the diradicaloids and conductive ionic liquid is fabricated, showing a remarkably high thermal response of 1100% at 0.5 W cm(-2).