One-Pot In Situ Construction of a Highly Stable Acylhydrazone-Derived Dy₉ Cluster with Photodynamic Sterilization Property

The extremely low stability of lanthanide clusters with precise structures and nanometer dimensions in aqueous solutions limits their application in the field of photodynamic sterilization. In this study, an hourglass-shaped nine-nucleated Dy₉ cluster (<b>1</b>) with excellent light-driven reactive oxygen species (ROS) generation ability and photodynamic sterilization property was constructed using acylhydrazone multidentate chelating ligands obtained via an in situ reaction. The eight chelating ligands were distributed outside cluster <b>1</b>, tightly wrapping the cluster core, thus preventing solvent molecules from attacking the cluster nucleus and ensuring the stability of cluster <b>1</b> in solution, which was demonstrated via X-ray diffraction and high-resolution electrospray ionization mass spectrometry (HRESI-MS). Time-dependent HRESI-MS monitoring of the self-assembly process of cluster <b>1</b> allowed two possible self-assembly mechanisms. The heavy atom effect of multiple Dy(III) ions in the Dy₉ cluster enhanced the ISC pathway through spin-orbit coupling, promoting energy transfer from the excited singlet state (S₁) to the triplet state (T₁), which was stabilized, inducing the generation of more ROS. Cluster <b>1</b> showed a remarkable sterilization effect due to the generation of abundant ROS under light irradiation conditions. To our knowledge, this is a rare instance of lanthanide clusters with photodynamic sterilization, providing new horizons for the construction of fast and efficient sterilizers.