Atomically Precise Multimetallic Semiconductive Nanoclusters with Optical Limiting Effects

For the first time, multinuclear noble-metal clusters have been successfully stabilized by Ti-oxo clusters. Two unprecedented Ag-6@Ti-16-oxo nanoclusters with precise atomic structures were prepared and characterized. The octahedral Ag-6 core has strong Ag-Ag bonds (ca. 2.7 angstrom), and is further stabilized by direct Ag-O-Ti coordination interactions. Moreover, as a result of different acidic/redox conditions in synthesis, the Ag-6 core can adopt diverse geometric configurations inside the Ti-16-O shell. Correspondingly, structural differences greatly influence their optical limiting effects. The transmittance reduction activity of the clusters towards 532nm laser shows a nearly linear concentration dependence, and can be optimized up to about 43%. This work not only opens a new direction for multimetallic semiconductive nanoclusters with interesting optical properties, but also provides molecular models for important noble-metal/TiO2 heterogeneous materials.