Facile preparation of N, S co-doped carbon dots and their application to a novel off-on fluorescent probe for selective determination of Hg2+

In this work, citric acid (CA) and glutathione (GSH) were selected as the raw materials for preparation carbon dote co-doped with N and S (NS-CDs) via microwave heating method. The obtained NS-CDs displayed stable and strong blue luminescence with a maximum emission (lambda em) wavelength of 442 nm and a maximum excitation (lambda ex) wavelength of 371 nm, and their fluorescence quantum yield (FLQY) was 10.9%. The fluorescence of NS -CDs was quenched by silver nanoparticles (AgNPs) through a combination of static quenching effect and inner filter effect (IFE), and could be recovered by Hg2+ even at nanomolar levels ascribing to redox reaction between Hg-2+ and AgNPs. Based upon this phenomenon, a novel off-on fluorescent probe (NS-CDs -AgNPs) for deter-mination trace Hg-2+ in aqueous solution was constructed using the obtained NS-CDs and AgNPs. Under optimal conditions, NS-CDs -AgNPs exhibited a wide linearity range of 10-90 nM (R-2 = 0.993) for (Hg)(2)+and a low LOD of 4.2 nM. NS-CDs -AgNPs was successfully utilized for monitoring Hg-2+ in real water samples with the recoveries of 91.4-108.6% (RSD < 5.84%), which indicated that the fluorescent probe has enormous application potential to detect trace Hg-2+ in real water samples.

Automated summary

In this study, citric acid and glutathione were used as raw materials to prepare nitrogen and sulfur co-doped carbon dots via microwave heating. The obtained carbon dots exhibited stable blue luminescence and could be quenched by silver nanoparticles and recovered by mercury ions, which facilitated the construction of a highly sensitive fluorescent probe for detecting trace Hg2+.