Atomically precise clusters of Au are of significant interest due to their unusual and tunable properties that differ from that of bulk material or larger nanostructures. These properties are remarkably sensitive to minor changes in electronic and geometric structure, each being determined by the composition of the metal core and ligand shell. The Au₁₁ core cluster is one of the most ubiquitous ligand-protected Au clusters, largely due to its small size and facile synthesis, though it lacks luminescence and is relatively unstable compared to other common clusters.
Herein, we report the novel synthesis of a Pt-doped PtAu₁₀(PPh₃)₇Br₃ cluster. The geometric structure and size of the parent Au₁₁(PPh₃)₇Br₃ nanocluster was maintained upon hetero-metal doping, as confirmed by single crystal X-ray crystallography and transmission electron microscopy. Absorption spectroscopy and electrochemical analysis revealed significant changes in electronic structure due to the single Pt dopant, resulting in a large expansion in the HOMO-LUMO gap and enhanced photoluminescence (λ_max = 700 nm, Φ = 1.88%). Additionally, the photothermal stability of the alloy clusters was found to be markedly improved from that of the homo-metal clusters. We also synthesized and characterized iodide-protected PtAu₁₀ clusters, demonstrating the ligand-dependent properties of the cluster’s luminescence. Finally, we demonstrate the application of the PtAu₁₀(PPh₃)₇Br₃ cluster’s NIR photoluminescence in the fluorescent detection of a nitroaromatic compound, with a limit-of-detection of 9.52 μM (1.74 ppm).

Catherine Connolly

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