LAUSR

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.