Ultra-sensitive green spectrofluorimetric approach for quantification of Hg (II) in environmental samples (water and fish samples) using cystine@MnO 2 dots.

Mercury (Hg 2+ ) is natural element present in food such as fish, water and soils, exposure to mercury led to severe toxic effect on nervous, digestive, and immune system. Herein, a novel, green and environmentally friendly fluorescent probe decorated cysteine MnO 2 quantum dots (Cys@MnO 2 QDs) has been synthesized. This synthesis was carried out through a simple ultrasonic technique with the aid of cysteine for fabricating of Cys@MnO 2 QDs for estimation of Hg in fish and water samples. The morphological study of Cys@MnO 2 QDs have been fully characterized using HRTEM, Zeta potential analysis, fluorescence, UV-VIS, and IR spectroscopy. The fluorescence of the synthesized Cys@MnO 2 QDs was significantly quenched by gradually increasing Hg (II) concentration. Furthermore, the quenching mechanism based on the Hg-S bonding strengthens the utility of the Cys@MnO 2 QDs as a novel luminescent nanoprobe. The estimation of Hg was found in the range of (0.7 - 100.0 ng mL -1 ) with LOQ equal to 0.30 ng mL -1 . The Cys@MnO 2 QDs is fluorescent probe with various benefits like being quick, easy, affordable, and environmentally friendly that easily applied for food manufacturing and for public health improvement.