The tetrahedral structure and luminescence properties of Bi-metallic Pt(1)Ag(28)(SR)(18)(PPh(3))(4) nanocluster

The atomic-structure characterization of alloy nanoclusters (NCs) remains challenging but is crucial in order to understand the synergism and develop new applications based upon the distinct properties of alloy NCs. Herein, we report the synthesis and X-ray crystal structure of the Pt(1)Ag(28)(S-Adm)(18)(PPh(3))(4) nanocluster with a tetrahedral shape. Pt(1)Ag(28) was synthesized by reacting Pt(1)Ag(24)(SPhMe(2))(18) simultaneously with Adm-SH (1-adamantanethiol) and PPh(3) ligands. A tetrahedral structure is found in the metal framework of Pt(1)Ag(28) NC and an overall surface shell (Ag(16)S(18)P(4)), as well as discrete Ag(4)S(6)P(1) motifs. The Pt(1)Ag(12) kernel adopts a face-centered cubic (FCC) arrangement, which is observed for the first time in alloy nanoclusters in contrast to the commonly observed icosahedral structure of homogold and homosilver NCs. The Pt(1)Ag(28) nanocluster exhibits largely enhanced photoluminescence (quantum yield QY = 4.9%, emission centered at ∼672 nm), whereas the starting material (Pt(1)Ag(24) NC) is only weakly luminescent (QY = 0.1%). Insights into the nearly 50-fold enhancement of luminescence were obtained via the analysis of electronic dynamics. This study demonstrates the atomic-level tailoring of the alloy nanocluster properties by controlling the structure.