Reversible Interconversion\nbetween Ag<sub>2</sub> and\nAg<sub>6</sub> Clusters and Their Responsive Optical Properties

The exploration of structural interconversion in clusters\ntriggered\nby external stimuli has attracted significant interest due to its\npotential to elucidate structure–property relationships of\nmetal clusters. In this study, two types of silver clusters, Ag<sub>2</sub> and Ag<sub>6</sub>, are synthesized. Interestingly, the clusters\nexhibit reversible transformations in response to changes in the solvent\nconditions. The structures and optical properties of these clusters\nare thoroughly characterized using techniques such as mass spectrometry,\nsingle-crystal X-ray diffraction, photoluminescence, and radioluminescence\nspectroscopy. While both Ag<sub>2</sub> and Ag<sub>6</sub> display\nexcellent photoluminescence properties, Ag<sub>2</sub> demonstrates\nsuperior performance in X-ray radioluminescence compared to Ag<sub>6</sub>. Flexible scintillator films fabricated from Ag<sub>2</sub> clusters exhibit outstanding X-ray imaging capabilities, achieving\na spatial resolution of 15.0 lp/mm and an impressive detection limit\nfor an X-ray dose of 0.58 μGy s<sup>–1</sup>. This detection\nlimit is nearly 10 times lower than the typical dose rate used in\nX-ray diagnostics (5.5 μGy s<sup>–1</sup>). This work\nintroduces a novel approach for designing thiol-free silver clusters\ncapable of solvent-dependent reversible interconversion, offering\nnew insights into the development of silver clusters for advanced\nX-ray imaging applications.