Transformation of Black Phosphorus through Lattice Reconstruction for NIR-II-Responsive Cancer Therapy

The photothermal performance of black phosphorus (BP) in the near infrared (NIR)-II bio-window (1000-1500 nm) is low, which limits its biomedical applications. Herein, ultrasmall nickel phosphide quantum dots (Ni₂ P QDs) are synthesized with BP quantum dots (BPQDs) as the template by topochemical transformation. The size of Ni₂ P QDs is ≈3.5 nm, similar to that of BPQDs, whereas the absorption and photothermal conversion efficiency of Ni₂ P QDs at 1064 nm (43.5%) are significantly improved compared with those of BPQDs. To facilitate in vivo applications, an Ni₂ P QDs-based liposomal nano-platform (Ni₂ P-DOX@Lipo-cRGD) is designed by incorporation of Ni₂ P QDs and doxorubicin (DOX) into liposomal bilayers and the interior, respectively. The encapsulated DOX is responsively released from liposomes upon 1064-nm laser irradiation owing to the photothermal effect of Ni₂ P QDs, and the drug release rate and amount are controlled by the light intensity and exposure time. In vivo, experiments show that Ni₂ P-DOX@Lipo-cRGD has excellent tumor target capability and biocompatibility, as well as complete tumor ablation through the combination of photothermal therapy and chemotherapy. The work provides a new paradigm for the NIR-II transformation of nano-materials and may shed light on the construction of multifunctional nano-platforms for cancer treatment.