Small organic photothermal agents (SOPTAs) that absorb in the second near-infrared (NIR-II, 1000–1700 nm) window are highly desirable in photothermal therapy for their good biocompatibility and deeper tissue penetration. However, the design of NIR-II absorbing SOPTAs remains a great challenge. Herein, we report that molecular engineering of BF₂ complex via strengthening the donor-acceptor conjugation and increasing the intramolecular motions is an efficient strategy to achieve NIR-II absorbing SOPTAs with high photothermal performance. Based on this strategy, a BF₂ complex, BAF4, was designed and synthesized. BAF4 exhibits an intense absorption maximum at 1000 nm and negligible fluorescence. Notably, the nanoparticles of BAF4 achieve a high photothermal conversion efficiency value of 80 % under 1064 nm laser irradiation (0.75 W cm⁻²). In vitro and in vivo studies reveal the great potential of BAF4 nanoparticles in photoacoustic imaging-guided photothermal therapy in the NIR-II window.

中文翻译：

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一种基于二氟化硼复合物的光热剂，具有 80% 的光热转换效率，用于 NIR-II 窗口中的光热治疗

在第二个近红外（NIR-II，1000-1700 nm）窗口中吸收的小型有机光热剂（SOPTA）因其良好的生物相容性和更深的组织渗透而在光热治疗中非常受欢迎。然而，NIR-II 吸收 SOPTA 的设计仍然是一个巨大的挑战。在此，我们报告通过加强供体-受体共轭和增加分子内运动对 BF ₂复合物进行分子工程是实现具有高光热性能的 NIR-II 吸收 SOPTA 的有效策略。基于这个策略，一个 BF ₂复合物 BAF4 被设计和合成。BAF4 在 1000 nm 处表现出强烈的吸收最大值和可忽略的荧光。值得注意的是，BAF4 的纳米粒子在 1064 nm 激光照射（0.75 W cm ^-2）下实现了 80% 的高光热转换效率值。体外和体内研究揭示了 BAF4 纳米粒子在 NIR-II 窗口中光声成像引导的光热治疗中的巨大潜力。