Lanthanide based dual-emission fluorescent probe for detection of mercury (II) in milk

It is highly desirable to develop a simple and sensitive method for Hg2+ detection because of the dangerous nature of Hg2+. In this work, we prepared a dual-emission fluorescent probe for Hg2+ detection by combining two lanthanide chelates with different emission wavelengths. Green-emitting terbium (Tb3+) chelates as reference signals were embedded into SiO2 nanoparticles and red-emitting europium (Eu3+) chelates as response units were covalently linked to the surface of silica shell. Upon the addition of Hg2+, the fluorescence of Eu3+ chelates can be selectively quenched, while the fluorescence of Tb3+ chelates remained unchanged. As a kind of Hg2+ nanosensor, the dual-emission fluorescent probe exhibited excellent selectivity to Hg2+ and high sensitivity up to 7.07 nM detection limit. The Hg2+ levels in drinking water and milk samples were determined by using the dual-emission fluorescent probe with satisfied recovery. Additionally, our probe has a long enough fluorescence lifetime, which can avoid the interference from autofluorescence of the biological samples. We envision that the proposed probe could find great potential applications for ultrasensitive time-resolved fluorometric assays and biomedical imaging in the future.