Ultrasensitive Green Spectrofluorimetric Approach for Quantification of Hg(II) in Environmental Samples (water and Fish Samples) Using Cysteine@MnO Dots

Mercury (Hg ) is a natural element present in foods such as fish, water and soil. Exposure to mercury leads to severe toxic effects on the nervous, digestive, and immune systems. Here, a novel, green, and environmentally friendly fluorescent probe decorated with cysteine/MnO quantum dots (Cys@MnO QDs) was synthesized. This synthesis was carried out using a simple ultrasound technique with the aid of cysteine for fabricating Cys@MnO QDs to estimate Hg levels in fish and water samples. In this morphological study, Cys@MnO QDs were fully characterized using high-resolution transmission electron microscopy, zeta potential analysis, fluorescence, ultraviolet-visible and infrared spectroscopy. The fluorescence of the synthesized Cys@MnO QDs was significantly quenched by gradually increasing the Hg(II) concentration. The quenching mechanism based on the Hg-S bonds strengthened the utility of the Cys@MnO QDs as a novel luminescent nanoprobe. The estimation of Hg was linear in the concentration range 0.7-100.0 ng mL with a limit of quantitation equal to 0.30 ng mL . The Cys@MnO QDs are fluorescent probes with various benefits such as speed, ease of use, cost- effective, and being environmentally friendly; they are easily applied in food manufacturing and for public health improvement.