LAUSR

Abstract 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 Hg 2+ 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 Hg 2+ and binding result in quenching of fluorescence. This effect can be used to quantify Hg 2+ in concentration down to 10 pM and with detection limit as low as 0.24 pM. The ultrasensitive detection of Hg 2+ ions is demonstrated by analyzing Hg 2+ -spiked water and tap-water samples.