An All‐rounder for NIR‐II Phototheranostics: Well‐Tailored 1064 nm Excitable Molecule for Photothermal Combating Orthotopic Breast Cancer

Abstract The second near‐infrared (NIR‐II, 1000–1700 nm) light‐activated organic photothermal agent that synchronously enables satisfying NIR‐II fluorescence imaging is highly warranted yet rather challenging on the basis of the overwhelming nonradiative decay. Herein, such an agent, namely TPABT‐TD, was tactfully designed and constructed via employing benzo[ c ]thiophene moiety as bulky electron donor/π‐bridge and tailoring the peripheral molecular rotors. Benefitting from its high electron donor–acceptor strength and finely modulated intramolecular motion, TPABT‐TD simultaneously exhibits ultralong absorption in NIR‐II region, intense fluorescence emission in the NIR‐IIa (1300–1500 nm) region as nanoaggregates, and high photothermal conversion upon 1064 nm laser irradiation. Those intrinsic advantages endow TPABT‐TD nanoparticles with prominent fluorescence/photoacoustic/photothermal trimodal imaging‐guided NIR‐II photothermal therapy against orthotopic 4T1 breast tumor with negligible adverse effect.