Zinc nitride quantum dots as an efficient probe for simultaneous fluorescence detection of Cu 2+ and Mn 2+ ions in water samples.

The exceptional ascending heights of graphene (carbon) and boron nitride nanostructures have invited scientists to explore metal nitride nanomaterials. Herein, Zn 3 N 2 quantum dots (QDs) were prepared via a simple hydrothermal route from the reaction between zinc nitrate hexahydrate and ammonia solution that possess efficient strength towards sensing applications of metal ions (Cu 2+ and Mn 2+ ). The as-prepared Zn 3 N 2 QDs show bright fluorescence, displaying an emission peak at 408 nm upon excitation at 320 nm, with a quantum yield (QY) of 29.56%. It was noticed that the fluorescence intensity of Zn 3 N 2 QDs linearly decreases with the independent addition of Cu 2+ and Mn 2+ ions, displaying good linearity in the ranges 2.5-50 µM and 0.05-5 µM with detection limits of 21.77 nM and of 63.82 nM for Cu 2+ and Mn 2+ ions, respectively. The probe was successfully tested for quantifying Cu 2+ and Mn 2+ in real samples including river, canal, and tap water, providing good recoveries with a relative standard deviation  < 2%. Furthermore, the masking proposition can successfully eliminate the interference if the two metal ions exist together. It was found that thiourea is efficiently able to mask Cu 2+ and selectively quenches Mn 2+ , and L-cysteine is able to halt the quenching potential of Mn 2+ and is selectively able to sense Cu 2+ . The Zn 3 N 2 QDs provide a simple way for the simultaneous detection of both Cu 2+ and Mn 2+ ions in environmental samples at low sample preparations requirements.