Fluorometric carbon-dots nanosensor for the detection of hexavalent chromium in water

The detection of trace residues of hexavalent chromium (Cr(VI)) in water is crucial for assessing ecological hazards due to its high cytotoxicity and carcinogenic properties. In this study, we have developed a selective and sensitive fluorescent sensor utilizing carbon dots (CDs) with an average size of 2 nm. The CDs is synthesized via a low-cost and facile one-step method without the need for additional heteroatoms. The CDs-based sensor exhibits superior selectivity, even in the presence of environmentally relevant cations, and can detect Cr(VI) over a concentration range of 1–1000 μM (with a linear range of 1 – 125 μM and R2 ≥ 0.998). The detection limit of the sensor is found to be 0.6 μM (equivalent to 31 μg L−1), which is below the value of 50 μg L−1 for drinking water guide-lined by the World Health Organization. This performance can be attributed to the combination of inner filter effect with the static quenching effect between the as-synthesized CDs and Cr(VI). Furthermore, we demonstrate the applicability of the CDs-based sensor for Cr(VI) detection in real samples of drinking water and tap water.