Unlocking the Photoluminescence and Photostability of Au₁₁ Clusters through Pt-Mediated Band-Gap Engineering

Au nanoclusters often demonstrate useful optical properties such as visible/near-infrared photoluminescence, in addition to remarkable thermodynamic stability owing to their superatomic behavior. The smallest of the 8e^- superatomic Au nanoclusters, Au₁₁, has limited applications due to its lack of luminescence and relatively low stability. In this work, we investigate the introduction of a single Pt dopant to the center of a halide- and triphenylphosphine-ligated Au₁₁ nanocluster, affording a cluster with a proposed molecular formula PtAu₁₀(PPh₃)₇Br₃. Electrochemical and spectroscopic analysis reveal an expansion of the HOMO-LUMO gap due to the Pt dopant, as well as relatively strong near-infrared (NIR) photoluminescence which is atypical for an M₁₁ cluster (λ_max = 700 nm, Φ = 1.88 %). The Pt dopant additionally boosted photostability; more than tenfold. Lastly, we demonstrate the application of the PtAu₁₀ cluster's NIR photoluminescence in the detection of the nitroaromatic compound 2,4-dinitrotoluene, with a limit-of-detection of 9.52 μM (1.74 ppm). The notable ability of a single central Pt dopant to unlock photoluminescence in a non-luminescent nanocluster highlights the advantages of heterometal doping in the tuning of both the optical and thermodynamic properties of Au nanoclusters.