Self-Photooxidation-Restructuring Enables NIR-II Absorption of Carbon Dots for Cancer Phototherapy

• • The 'self-photooxidation-restructuring' strategy achieves a significant redshift of carbon dot absorption into the NIR-II window (900-1700 nm), overcoming the synthetic complexity and lack of precise control in existing methods. • • N-CDs exhibit a photothermal conversion efficiency of 71.33% under 1064 nm laser irradiation, enabling effective photoacoustic imaging-guided photothermal therapy in tumors. • • Mechanistic studies (XPS, FTIR, NMR, EPR) confirm that UV-induced singlet oxygen oxidizes aldehyde groups to carboxyl groups and generates carbon radicals, promoting new C=C bond formation between aromatic domains. • • The N-CDs demonstrate enhanced donor-acceptor interactions, which are critical for the redshifted absorption and high photothermal performance, offering a scalable and controllable route for NIR-II carbon dot synthesis.