The tetrahedral structure and luminescence properties of Bi-metallic PtAg(SR)(PPh) 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 PtAg(S-Adm)(PPh) nanocluster with a tetrahedral shape. PtAg was synthesized by reacting PtAg(SPhMe) simultaneously with Adm-SH (1-adamantanethiol) and PPh ligands. A tetrahedral structure is found in the metal framework of PtAg NC and an overall surface shell (AgSP), as well as discrete AgSP motifs. The PtAg 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 PtAg nanocluster exhibits largely enhanced photoluminescence (quantum yield QY = 4.9%, emission centered at ∼672 nm), whereas the starting material (PtAg NC) is only weakly luminescent (QY = 0.1%). Insights into the nearly 50-fold enhancement of luminescence were obtained the analysis of electronic dynamics. This study demonstrates the atomic-level tailoring of the alloy nanocluster properties by controlling the structure.