NIR Light‐Driving Barrier‐Free Group Rotation in Nanoparticles with an 88.3% Photothermal Conversion Efficiency for Photothermal Therapy

Abstract Traditional photothermal therapy requires high‐intensity laser excitation for cancer treatments due to the low photothermal conversion efficiency (PCE) of photothermal agents (PTAs). PTAs with ultra‐high PCEs can decrease the required excited light intensity, which allows safe and efficient therapy in deep tissues. In this work, a PTA is synthesized with high PCE of 88.3% based on a BODIPY scaffold, by introducing a CF 3 “barrier‐free” rotor on the meso ‐position (tfm‐BDP). In both the ground and excited state, the CF 3 moiety in tfm‐BDP has no energy barrier to rotation, allowing it to efficiently dissipate absorbed (NIR) photons as heat. Importantly, the barrier‐free rotation of CF 3 can be maintained after encapsulating tfm‐BDP into polymeric nanoparticles (NPs). Thus, laser irradiation with safe intensity (0.3 W cm −2 , 808 nm) can lead to complete tumor ablation in tumor‐bearing mice after intravenous injection of tfm‐BDP NPs. This strategy of “barrier‐free rotation” provides a new platform for future design of PTT agents for clinical cancer treatment.