“Turn-on” Fluorescence Detection of Lead Ions Based on Accelerated Leaching of Gold Nanoparticles on the Surface of Graphene

A novel, platform for effective "turn-on" fluorescence sensing of lead ions (Pb2+) in aqueous solution was developed based on gold nanoparticle (AuNP)-functionalized graphene. The AuNP-functionalized graphene exhibited minimal background fluorescence because of the extraordinarily high quenching ability of AuNPs. Interestingly, the AuNP-functionalized graphene underwent fluorescence restoration as well as significant enhancement upon adding Pb2+, which was attributed to the fact that Pb2+ could accelerate the leaching rate. of the AuNPs on graphene surfaces in the presence of both thiosulfate (S2O32-) and 2-mercaptoethanol (2 ME) Consequently, this could be utilized as the basis for selective defection of Pb2+. With the optimum conditions chosen the:relative fluorescence intensity showed good linearity versus logarithm concentration of Pb2+ in the range of 50-1000 nM (R = 0.9982), and a detection limit of 10 nM. High selectivity over common coexistent metal ions was also demonstrated: The practical application had been carried out for determination of Pb2+ in tap water and mineral water samples. The Pb2+-specific "turn-on" fluorescence sensor, based on Pb2+ accelerated leaching of AuNPs on the surface of graphene, provided new opportunities for highly sensitive and selective Pb2+ detection in aqueous media.