Fabrication of Fluorescence Turn-off-on Sensor Based on g-C3N4 Quantum Dots and MgFe Layered Double Hydroxide for the Detection of Citrate

We fabricated a new and selective fluorescent sensor for the detection of citrate by employing g-C 3 N 4 quantum dots (g-CNQDs) and MgFe layered double hydroxide (MgFe-LDH). The g-CNQDs interacted with MgFe-LDH via electrostatic interaction and the fluorescence of g-CNQDs was effectively quenched by MgFe-LDH due to inner filter effect. Upon addition of citrate, the fluorescence of the g-CNQDs was significantly enhanced, arising from the replacement of g-CNQDs by citrate because citrate competed with g-CNQDs to form more stable complexes with MgFe-LDH. Therefore, we developed a “turn-off–on” fluorescence assay method for the detection of citrate. This method enabled the selective detection of citrate with linear range of 0.5–3.0 μM and 3.0–10.0 μM with a 12.3 nM limit of detection. This method exhibited advantages including easy preparation, environmentally friendly process and rapid response toward citrate.