The tetrahedral structure and luminescence properties of Bi-metallic Pt1Ag28(SR)18(PPh3)4 nanocluster

Abstract

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 Pt₁Ag₂₈(S-Adm)₁₈(PPh₃)₄ nanocluster with a tetrahedral shape. Pt₁Ag₂₈ was synthesized by reacting Pt₁Ag₂₄(SPhMe₂)₁₈ simultaneously with Adm-SH (1-adamantanethiol) and PPh₃ ligands. A tetrahedral structure is found in the metal framework of Pt₁Ag₂₈ NC and an overall surface shell (Ag₁₆S₁₈P₄), as well as discrete Ag₄S₆P₁ motifs. The Pt₁Ag₁₂ 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 Pt₁Ag₂₈ nanocluster exhibits largely enhanced photoluminescence (quantum yield QY = 4.9%, emission centered at ∼672 nm), whereas the starting material (Pt₁Ag₂₄ 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.