Carbon dots-silver nanoparticles fluorescence resonance energy transfer system as a novel turn-on fluorescent probe for selective determination of cysteine

In this paper, we investigated the interaction of carbon dots (C-dots) prepared from orange juice with silver nanoparticles (AgNPs) using fluorescence spectroscopy. It was found that AgNPs efficiently quench the fluorescence of C-dots as a result of fluorescence resonance energy transfer (FRET). Thus, a novel FRET system between C-dots (as the donor) and AgNPs (as the acceptor) was introduced. Moreover, it was found that cysteine even at nanomolar levels could recover the fluorescence of C-dots due to the competitive adsorption of this compound onto AgNPs. This was exploited to design a simple and selective method for the determination of cysteine in the concentration range from 6.0 to 300 nM, with a detection limit of 4.0 nM. Cysteine was determined by this method in human plasma and urine samples with satisfactory results. (C) 2015 Elsevier B.V. All rights reserved.