Greatly Enhanced Photoabsorption and Photothermal Conversion of Antimonene Quantum Dots through Spontaneously Partial Oxidation

Two-dimensional quantum dots (2DQDs), as promising photothermal agents (PTAs) in photothermal therapy (PTT) to malignant tumors, have been widely studied experimentally, whereas the superior photoabsorption and photothermal conversion mechanisms remain unclear. In this work, we present the first excited-state dynamics study on the PTT of 2D antimonene (AM) QDs by employing time-dependent density functional theory and ab initio nonadiabatic molecular dynamics calculations. Surprisingly, pristine AMQDs themselves are not good PTAs due to weak photoabsorption and low photothermal conversion performance. The superior PTT capacity of AMQDs actually derives from the spontaneously partial oxidation. The partial oxidation introduces additional band edge states, which not only broaden the optical absorption range but also strengthen the transition dipole moment. More importantly, the oxidation doubles the nonradiative transition rate arising from the increased nonradiative coupling, which greatly promotes the release of photogenerated electron energy and accelerates the photothermal conversion efficiency. The in-depth insight unveiled here should be of fundamental importance and benefit for efficient utilization of 2DQDs in biomedical field.