Sensitive fluorescence detection of mercury(ii) in aqueous solution by the fluorescence quenching effect of MoS2 with DNA functionalized carbon dots.

A rapid and sensitive fluorescent sensor based on the MoS2 nanosheet/DNA/carbon dot nanoassembly has been developed towards the detection of mercury(ii) present in environmental samples. Bio-carbon dots (CDs) having strong fluorescence maxima at 451 nm were synthesized via one-step treatment with honey under low temperature carbonization. These CDs were nearly spherical with good size distribution and excellent monodispersity, and the average sizes of CD were around 2-4 nm as evidenced from transmission electron microscopy. The conjugation of DNA strands on the surface of the carbon dots provided an efficient fluorescent probe. The fluorescence of the MoS2 nanosheet/DNA/carbon dot nanoassembly enhanced gradually with the increase in the concentration of Hg2+ ions and the detection limit was found to be 1.02 nM. Furthermore, the fluorescence intensity was found to be linear with the concentration of Hg2+ ions in the range from 0 to 10 nM and their respective coefficient of determination was found to be 0.93676 and 0.98178. The present MoS2 nanosheet/DNA/carbon dot nanoassembly is highly selective toward Hg2+ ions over a wide range of metal ions tested.