Vacancy-enhanced generation of singlet oxygen for photodynamic therapy.

Oxygen vacancy (OV) engineering in semiconductors can greatly enhance the separation of photo-induced electron-hole pairs, thereby enhancing the photocatalytic activity. Taking inspiration from this, we prepared a novel BiOBr-H/Rub2d composite by functionalizing OV-rich BiOBr (named BiOBr-H) with a carboxyl functionalized ruthenium photosensitizer (Ru(bpy)2C-pyCl2, abbreviated as Rub2d), which was then successfully applied for photodynamic therapy (PDT). Density functional theory (DFT) calculations confirmed efficient electron transfer from the Rub2d complex to the intermediate energy level of BiOBr-H under visible light irradiation. In vitro and in vivo studies demonstrated that BiOBr-H/Rub2d was a superior agent for photodynamic therapy compared with the free ruthenium complex. The theoretical and experimental data presented thus reveal for the first time that abundant OVs in BiOBr-H can significantly improve the photocatalytic activity of a photosensitizer, resulting in the generation of more reactive oxygen species to enhance PDT. The findings of this study thus offer a new strategy for the development of highly efficient cancer therapies.