Janus-like BxC/C Quantum Sheets with Z-Scheme Mechanism Strengthen Tumor Photothermal-Immunotherapy in NIR-II Biowindow

Carbon dots (CDs) are one of the most popular photothermal agents (PTAs) as a noninvasive strategy for tumor treatment. However, because of the inherent dominant fluorescent emission, the CDs-based PTAs hardly achieve a single photothermal conversion, which causes low photothermal conversion efficiency and poor photothermal performance. In this regard, finding a new CDs-based material system to greatly restrain its fluorescence to enhance its photothermal conversion efficiency is highly required, however, it is still a grand challenge. Herein, a kind of Z-scheme CDs-based PTAs consisting of 2D ultrathin nonmetallic BxC/C Janus quantum sheets (BxC/C JQSs) is reported to greatly enhance the photothermal conversion efficiency. It is demonstrated that the heterogeneous growth of Z-scheme BxC/C JQSs enables the NIR-driven quick injection of hot electrons from C into the conjugated BxC, realizing a single conversion of light to heat, and resulting in a high photothermal conversion of 60.0% in NIR-II. Furthermore, these new Z-scheme BxC/C-polyethylene glycol JQSs display outstanding biocompatibility and show effective tumor elimination outcome both in vitro and in vivo through the synergistic photothermal-immunotherapy in the NIR-II biowindow with undetectable harm to normal tissues.