Fluorescent Determination of Mercury(II) by Green Carbon Quantum Dots Synthesized from Eggshell Membrane

Carbon quantum dots (CQDs), as a new carbonaceous nanomaterial, have attracted considerable attention due to their excellent properties. In this work, eggshell membrane (ESM), an excellent carbon source that is very easy to obtain, was used to synthesize water-soluble and fluorescent CQDs with a rapid, environmentally friendly and waste-recycling hydrothermal method. The synthesized functionalized CQDs showed superior water dispersibility and stability with a maximum fluorescence emission peak at 420 nm. The fluorescence quantum yield was approximately 9.6% under the selected synthesis conditions. A new label-free fluorescent method for the selective determination of Hg2+ was developed with a detection limit of 2.6 μM using the inhibition of the CQDs fluorescence by the ions. The linear range of the detection is from 10 to 100 μM. The prepared CQDs have also been successfully applied to the determination of Hg2+ in water samples.