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

The exceptional ascending heights of graphene (carbon) and boron nitride nanostructures have invited scientists to explore metal nitride nanomaterials. Herein, ZnN 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 and Mn). The as-prepared ZnN 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 ZnN QDs linearly decreases with the independent addition of Cu and Mn 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 and Mn ions, respectively. The probe was successfully tested for quantifying Cu and Mn 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 and selectively quenches Mn, and L-cysteine is able to halt the quenching potential of Mn and is selectively able to sense Cu. The ZnN QDs provide a simple way for the simultaneous detection of both Cu and Mn ions in environmental samples at low sample preparations requirements.