Ellagic acid-functionalized fluorescent carbon dots for ultrasensitive and selective detection of mercuric ions via quenching

The authors report on a strategy for the fabrication of water soluble carbon quantum dots (CDs) functionalized with ellagic acid. They also demonstrate highly selective detection of Hg2+ ions in aqueous media via fluorescence quenching. The CDs were prepared via a one-step technique using tannic acid as the carbon source and directly surface functionalized during nanoparticle synthesis. Following photoexcitation at 210 nm they exhibit excitation -independent emission that peaks at 340 nm. The CDs display strong affinity for Hg2+ and binding result in quenching of fluorescence. This effect can be used to quantify Hg2+ in concentration down to 10 pM and with detection limit as low as 0.24 pM. The ultrasensitive detection of Hg2+ ions is demonstrated by analyzing Hg2+-spiked water and tap-water samples.