GENERATION AND STABILITY OF LUMINESCENT SILVER NANODOTS IN OXIDIZING ENVIRONMENTS

摘要

Silver nanodots consisting of a few silver atoms are becoming excellent fluorophores thanks to their small size, high brightness and excellent photostability. Initially, such clusters were prepared in noble gas matrices due to their vulnerability to oxidization. New protection groups has improved their stability in aqueous solution, leading to the synthesis of a series of spectrally-pure silver nanodots with emissions ranging from the blue to the near-IR. The exact structures of various silver nanodots remain unclear. We examined the photo-responses of various silver nanodots in oxidizing environments. Oxidants bleaches most of nanodot emitters, but only the red and near-IR emitters correlates with the formation of an oxidant-resistant blue emitter. The HPLC-MS indicates that the blue is an oxidized species. Based on such a unique phenomenon, we have demonstrated the advantage of the blue emitter as an imaging agent in oxidizing environments and designed ratiometric luminescence probes for the ultralow concentration detection. We also investigated the generation of silver nanodots by etching silver nanoparticles. The addition of chelating agents, such as polyamines or ssDNA molecules, accelerates the degradation of large silver nanoparticles to a stable stage of silver nanoparticles, which might be critical to the generation of emissive silver nanodots. The etching process is strongly pH dependent, and the binding between silver and the etching groups is crucial for efficient etching. The active centres are especially important for the formation of silver nanodots. We have shown that etching of silver nanoparticles can be an alternative to generate new silver nanodot emitters.