Synthesis of highly luminescent graphitized carbon dots and the application in the Hg2+ detection

Water-soluble graphitized carbon dots (GCDs) were synthesized by the one-step carbonization of ethylene glycol (EG) at 140 °C in the presence of concentrated sulfuric acid (H2SO4). Without any post-passivation, their quantum yield (QY) of photoluminescence (PL) reached 25%. The fluorescence of GCDs was located at about 400 nm with a full width at half maximum (FWHM) as small as ∼59 nm. The nearly invariable PL position in certain range of excitation wavelength concluded that the good PL of GCDs should be assigned to the bandlike transition similar to general semiconductor. Further investigation showed that they could be used as a label-free fluorescent probe in the selective and sensitive detection of Hg2+.

Water-soluble and graphitized carbon dots with photoluminescent quantum yield of 25% have been synthesized by the carbonization of ethylene glycol in the presence of concentrated sulfuric acid, which could be used successfully as a label-free fluorescent probe to selectively and sensitively detect Hg2+ even in real water.Highlights► Graphitized GCDs were prepared by the carbonization of EG in the presence of H2SO4. ► The photoluminescence QY of water-soluble GCDs reached ∼25% without any passivation. ► The GCDs showed good selectivity and sensitivity for the detection of Hg2+ ions. ► The PL of GCDs could be quenched by Hg2+ ions mainly through a static quenching mechanism.