Enhanced near-infrared electrochemiluminescence of Au nanoclusters treated with piperidine

Au nanoclusters (NCs) are considered a promising electrochemiluminescence (ECL) luminophore with biocompatibility and stability that make it suitable for use in bioelectrochemical investigations. The near-infrared (near-IR) ECL of Au NCs is of particular interest for biological applications. In this study, we report the significantly enhanced near-IR ECL of water-soluble Au NCs stabilized with glutathione, which was induced by treating the Au NCs with piperidine. The piperidine treatment of Au NCs enabled a 16-fold enhancement in the near-IR ECL of the NCs in the presence of triethylamine coreactants in water. Compared to the well-known near-IR ECL of Au NCs stabilized with bovine serum albumin (BSA) as a control, the near-IR ECL emission of the piperidine-treated Au NCs (p-Au NCs) was 8 times that of the BSA-stabilized Au NCs. Detailed control experiments suggested that the enhanced near-IR ECL of p-Au NCs could be attributed not to environmental effects (e.g., pH and chemical interference) and the surface ligand effect, but to the reduction of Au(I)-glutathione to Au(0)-glutathione in the NCs. Importantly, the piperidine treatment was also shown to be applicable to different types of Au NCs, such as well-established Au-22(SG)(18), for improving the ECL emission of the NCs in the near-IR region.