π-Bridge engineering strategy: tailoring S-xanthene dyes with strong absorption for high-efficiency photothermal therapy

, outstanding photothermal conversion efficiency (PCE) of 91.5%, and fluorescence quantum yield of 0.04%. Notably, the SCU-SX-T NPs facilitated high-resolution vascular imaging of the abdominal region and precise surgery in living mice, demonstrating their robust NIR-II fluorescence capability. Furthermore, NIR-II FLI/photothermal imaging (PTI)-guided tumor visualization and photothermal therapy (PTT) was successfully achieved. The integration of α-PD-L1 checkpoint blockade therapy led to significant inhibition of proximal tumor growth, highlighting the potential of this synergistic therapeutic strategy. Overall, this work provides a comprehensive NIR-II probe with excellent performance and ideas for the future design of NIR-II probes with high MEC.