Synchronously Manipulating the D-A Interaction and Planarity in Semiconducting Polymers to Achieve 84.7% Photothermal Conversion Efficiency for NIR-II Imaging-Guided Tumor Therapy

Exploiting photothermal agents with second-near-infrared (NIR-II, 1000-1700 nm) emission and a high photothermal conversion efficiency (PCE) is an appealing and challenging task. Herein, by simultaneously tailoring the D-A interaction and planarity in fluorophores, two donor-acceptor (D-A) -type semiconducting polymers (SPs), T-BTP and B-BTP, are constructed. Compared with T-BTP, B-BTP shows increased intramolecular interactions and improved molecular planarity, leading to bathochromic-shift absorption, NIR-II emission, and high PCE. Notably, the B-BTP NPs achieve a remarkable PCE of 84.7%, which is among the highest PCEs of SPs in NIR-II fluorescence imaging-guided photothermal therapy (PTT). Because of these promising features, B-BTP NPs are successfully used in NIR-II vascular imaging and cancer therapy. This study provides valuable guidelines for the development of high-performance NIR-II SPs. Via the regulation of donor-acceptor (D-A) interaction and molecule planarity, T-BTP and B-BTP are synthesized. Theoretical calculations evidence that B-BTP possesses more planar conjugated structures and stronger intramolecular D-A interactions than T-BTP. B-BTP NPs exhibit NIR emission extend to 1400 nm, and achieve a PCE of 84.7%, which is among the highest PCEs of semiconducting polymers (SPs) in fluorescence imaging-guided photothermal therapy (PTT). image