B,N-Co-doped graphene quantum dots as fluorescence sensor for detection of Hg2+ and F− ions

Herein, we develop a fluorescence sensing platform based on boron and nitrogen co-doped graphene quantum dots (B,N-GQDs), which are synthesized by a one-step bottom-up hydrothermal method. The prepared B,N-GQDs exhibit high-fluorescence quantum yield (75%) and long fluorescence lifetime (12.86 ns). In the B,N-GQDs–Hg2+ system, the fluorescence of B,N-GQDs is quenched with increasing Hg2+ concentration due to the affinity interaction between the surface functional groups of B,N-GQDs and Hg2+. Subsequently, the quenched fluorescence of the B,N-GQDs–Hg2+ system is gradually recovered with the addition of F− ions due to their strong affinity with Hg2+. The linear ranges for the detection of Hg2+ and F− ions are 0.2–2.6 μM and 0.25–7.0 mM, respectively, and the detection limits are 0.16 μM and 0.18 mM for Hg2+ and F− ions, respectively, which are below the regulatory level of 0.25 μM and 0.526 mM in the Integrated Wastewater Discharge Standard. Therefore, B,N-GQDs provide a facile and effective approach for the detection of both Hg2+ and F− ions with real-time monitoring and high-speed measuring.