Fluorescence-based selective nitrite ion sensing by amino-capped carbon dots

Abstract Nitrite ions pose a severe problem to human health justifying the need for fast and reliable detection of their presence in freshwater. Here we report a method to detect nitrite by photoluminescence of amino-rich carbon dots (C-dots). The dots are synthesized from p-phenylenediamine through a solvothermal treatment in ethanol. When nitrites ions are present in acidic water samples, the C-dots amino groups undergo diazotization and quench the C-dots emission at 535 nm, enabling the detection. The synthesis does not require a purification step as the unreacted species do not interfere with the nitrites sensing. The C-dots photoluminescence shows a linear quenching in the 6–75 µM concentration range which is below the concentration limits allowed for nitrites in drinking water. The effect of interferent metal ions in the water sample is also discussed, and an optimized protocol to achieve a precise readout is proposed.