Unlocking the Photoluminescence and Photostability of Au 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, Au, 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 Au nanocluster, affording a cluster with a proposed molecular formula PtAu(PPh)Br. 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 M cluster (λ = 700 nm, Φ = 1.88 %). The Pt dopant additionally boosted photostability; more than tenfold. Lastly, we demonstrate the application of the PtAu 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.