One-pot hydrothermal synthesis of high quantum yield orange-emitting carbon quantum dots for sensitive detection of perfluorinated compounds

We have prepared a new type of carbon quantum dots (CQDs) with orange fluorescence and high fluorescence quantum yield through a rapid hydrothermal approach. The CQDs were effective for sensitive and selective sensing of perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) in complex water samples. To prepare the CQDs, 4-(diethylamino) salicylaldehyde and phosphoric acid were heated at 200 °C for 1 h. This produced orange emitting CQDs with a fluorescence quantum yield of up to 47.1%. The synergetic effect of strong acid and high temperature accelerated the hydrothermal reaction. In addition, PFOS and PFOA can quench the fluorescence of the CQDs through an electron transfer mechanism. Fluorescence quenching by PFOS and PFOA was linear over a range of 0.05-1.0 μM and 0.1-1.5 μM, respectively, with corresponding limits of detection of 5 nM and 10 nM. The high chemical stability, stable fluorescence, and selective PFOS/PFOA response of the CQDs make them effective for PFOS/PFOA sensing in complex water samples. Thus, this simple and selective fluorescence quenching assay has great application potential in environmental monitoring and assessment.