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

Abstract

A novel platform for effective "turn-on" fluorescence sensing of lead ions (Pb 2+ ) 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 Pb 2+ , which was attributed to the fact that Pb 2+ could accelerate the leaching rate of the AuNPs on graphene surfaces in the presence of both thiosulfate (S 2 O 3 2− ) and 2-mercaptoethanol (2-ME). Consequently, this could be utilized as the basis for selective detection of Pb 2+. With the optimum conditions chosen, the relative fluorescence intensity showed good linearity versus logarithm concentration of Pb 2+ 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 Pb 2+ in tap water and mineral water samples. The Pb 2+ -specific "turn-on" fluorescence sensor, based on Pb 2+ accelerated leaching of AuNPs on the surface of graphene, provided new opportunities for highly sensitive and selective Pb 2+ detection in aqueous media.

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“…490,491 The quenching ability of the Au NPs was used to prepare a chemosensor for a "turn-on" fluorescence sensing of lead ions (Pb 2+ ), e.g. for the detection of organophosphate pesticides.…”

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