A dual-emission fluorescence sensor for ultrasensitive sensing mercury in milk based on carbon quantum dots modified with europium (III) complexes

A dual-emission fluorescence sensor was developed for Hg2+detection based on carbon quantum dots (CQDs) and Europium (III, Eu3+) complexes. The CQDs modified with Eu3+ complexes displayed dual-emission wavelengths of 443 and 617 nm. The dual-emission fluorescence intensity was significantly increased in the presence of Hg2+. The developed sensor displayed excellent selectivity and sensitivity with the detection range of 1–20 nM and detection limit of 0.2 nM. With increasing Hg2+ concentrations, developed sensor showed clear and regular color alternations from strong blue, light blue, lavender to deep purple observed by the naked eyes. The dual-emission method was successfully used for visual and ultrasensitive detection of Hg2+ in drinking water and milk samples with satisfied recovery from 97.6 % to 105.4 %. The sensor provides a generalizable platform for dual-emission fluorescence detection of Hg2+ based on rare earth ions-modified CQDs.