Highly Luminescent Nitrogen-Doped Carbon Dots as “Turn-On” Fluorescence Probe for Selective Detection of Melamine

In our work, a new and simple method for selective detection of melamine is established by developing a “turn-on” fluorescence probe based on nitrogen-doped carbon dots (N-CQDs) - iron ions (Fe³⁺). The N-CQDs have been facilely prepared by one-step simple hydrothermal reaction and it is highly luminescent that with 51% fluorescent quantum yield. In this sensor, the fluorescent intensity of N-CQDs was found to be efficient quenched by Fe³⁺, upon addition of melamine the fluorescent intensity of N-CQDs-Fe³⁺ could gradually recover, which may because of the competitive combination of Fe³⁺ and melamine leading to the departure of Fe³⁺ from the N-CQDs’ surface. Under optimum conditions, the fluorescence intensity has a good liner relationship with melamine in the range of 2.0 to 290 μM. The probe displayed good sensitivity toward melamine with a lower detection limit of 0.67 μM. In addition, this fluorescence probe has been used for the analysis of milk samples, demonstrating the fluorescence probe has potential application in the detection of melamine.