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-C3N4 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 mu M and 3.0-10.0 mu M with a 12.3nM limit of detection. This method exhibited advantages including easy preparation, environmentally friendly process and rapid response toward citrate.