A MELET- and IFE-based UV-visible luminescent ratiometric probe for quantization of mercury(II) and nitrofurantoin in environmental sewage

A novel fluorimetric ratiometric probe of green and eco-friendily nitrogen-enriched, oxygen-doped carbon nanodots (Cnanodots) was prepared for the quantitative analysis of mercury(II) (Hg^II) and nitrofurantoin (Nit) in the environmental sewage. The Cnanodots exhibits dual-emission peaks respectively at 345 and 445 nm under 285 nm excitation, with excitation-independent properties. Unexpectedly, this Cnanodots displays two obvious ratiometric responses to Hg^II and Nit through decreasing the signal at 345 nm and remaining invariable at 445 nm. Experimental results confirm that the highly sensitive analysis of Hg^II and Nit are achieved respectively based on matching energy-level electron transfer and inner filter effect mechanisms. The fluorescence (FL) ratiometric intensity of [FL_345nm/FL_445nm] expresses a good linear relationship with the concentration of Hg^II in the scope of 0.01-20 μM, while the logarithm of [Log(FL_0345nm-FL_345nm)] on the quenching degree of the probe by Nit also shows a good linear correlation within the range of 0.01-100 μM. The detection limits were calculated to be 4.14 nM for Hg^II, and 7.84 nM for Nit. Moreover, recovery experiments of Cnanodots for Hg^II and Nit sensing in real sewage samples obtained satisfactory results, comfirming the feasibility of practical application.