One-step synthesis of graphitic carbon nitride nanosheets with the help of melamine and its application for fluorescence detection of mercuric ions.

A facile, simple, and relatively environment-friendly hydrothermal approach was developed for one-step synthesis of graphitic carbon nitride nanosheets (GCNNs) using melamine and sodium citrate as the precursors. The prepared GCNNs emit strong fluorescence with a high quantum yield of 48.3%. The GCNNs were then characterized by various techniques including transmission electron microscopy, atomic force microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and UV-Vis absorption spectroscopy. In addition, the fluorescence quenching behavior of the GCNNS by mercuric ions (Hg2+) was exploited to fabricate a label-free fluorescence quenching sensor for sensitive and selective detection of Hg2+. The results showed that there existed a linear relationship between the fluorescence intensity and the concentration of Hg2+ from 0.001 to 1.0μM with a detection limit of 0.3nM. Finally, the sensor was successfully used to detection of Hg2+ in water and milk samples.