Highly selective fluorometric detection of para-nitrophenol from its isomers by nitrogen-doped graphene quantum dots

•A fluorometric sensing platform for para-nitrophenol was developed with the levels down to 0.29 μM.•The proposed analysis system was simple, fast, low-cost, effective, reliable and environment-friendly.•The proposed procedure was successfully applied for 4-NP detection in real water samples. Nitrogen-doped graphene quantum dots (N-GQDs) with blue fluorescence and excellent water-solubility and an average diameter of approximately 21 nm have been prepared via hydrothermal treatment of ammonium fluoroborate and trisodium citrate, with the average size in diameter about 21 nm. It was found that para-nitrophenol (4-NP) could dramatically quench the fluorescence of N-GQDs via static quenching because the good linearity of the Stern-Volmer equation (kq ≫ 2.0 × 1010L/(mol·s)) and the change in lifetime before and after the addition of 4-NP, which are different from that of its isomers and other analogs or metal ions. A fast and direct fluorimetric method with N-GQDs probe has thereby been developed for detecting 4-NP at concentrations from 0 to 20 μM, with a limit of detection of 0.29 μM. Furthermore, this proposed fluorimetric method was successfully applied to analyze 4-NP in real water samples, showing the feasible detection of trace 4-NP in complicated environmental water samples. The developed N-GQDs-based fluorimetric method is expected to be applied to the highly selective determination of 4-NP from its isomers, other analogs and general metal ions.