One-step photochemical synthesis of NIR-emissive and photothermal gold nanoclusters for biosensing application

An ecofriendly photochemical approach for the rapid and effective preparation of ultrasmall NIR-emissive gold-nanoclusters from photoirradiation of water-soluble glutathione (GSH) in the presence of HAuCl 4 is reported. The formation of gold nanoclusters with a glutathione shell (AuNCs-SG) is confirmed by optical measurements, mass spectrometry, NMR spectroscopy, and transmission electron microscopy. The AuNCs-SG exhibit good luminescence quantum yield (φ=1.1 %), long emission lifetime (1.22 μs), large Stoke’s shift (435 nm), and good photothermal yield conversion upon NIR-light excitation (η 808nm =33.9 %). The effect of the GSH ligand amount and AuNC compositions on the optical properties are extensively investigated. Bimetallic silver/gold-nanoclusters (AgAuNCs-SG) are also prepared and characterized to evaluate the effect of the Ag-doping on the optical properties of the nanocluster. The AuNCs-SG are successfully tested for the optical biosensing of Interleukine 6-antigen (IL6), with a LoD value of 57.5 fg mL −1 , through the formation of an IL6−antibody/nanocluster conjugate. The PL signal quenching is related to the amount of IL6 in the samples.