Nitrogen-doped graphene quantum dot for direct fluorescence detection of Al in aqueous media and living cells.

Graphene quantum dot (GQD) has been attractive in analytical science field due to its low toxicity, stable photoluminescence. Herein, nitrogen-doped GQD (N-GQD) was prepared by a facile solvothermal treatment of GO using dimethylformamide, and exhibited a green emission with 23.1% quantum yield. The N-GQD probe showed a selective and sensitive fluorescence enhancement response to Al, the mechanism might be the formation of a complex between Al and N-GQD constrained the photo-induced electron transfer (PET) process of N-GQD itself. With Benesi-Hildebrand equation, the binding constant and molar ratio between N-GQD and Al was calculated to be 4.6 × 10Lmol and 1:1 respectively. The pK value of N-GQD was also determined to be 4.4 by capillary electrophoresis. In pH 4.0 PBS solution, there was a good linear relation between the fluorescence intensity and the logarithm of concentration of Al in the range of 2.5-75μmolL, the limit of detection (3σ) was 1.3μmolL. This "Off - On" fluorescence method had been applied to accurate quantification of aluminum in hydrotalcite tablets. What's more, the fluorescence switch property of N-GQD was explored by alternate addition of Al and EDTA. The probe was also utilized for detection Al in living cells due to its excellent biocompatibility.