Nitrogen-Doped Highly Photoluminescent Carbon Dots Derived from Citric Acid and Guanidine Carbonate.

A facile one-pot hydrothermal method for fabricating nitrogen-doped carbon dots (N-CDs) was developed by using citric acid as a carbon source and guanidine carbonate as a nitrogen and carbon source. X-ray diffraction, X-ray photoelectron spectroscopy, and Fourier transform infrared spectra indicated that the N-CDs were rich in elemental nitrogen. They had excellent stability in the presence of various salt concentrations and under UV irradiation. The N-CDs exhibited high quantum yields (52%), as well as down-conversion and up-conversion photoluminescence. The N-CD photoluminescence was quenched in the presence of Hg2+ , while nearly no intensity changes were observed when in the presence of Na+ , Mg2+ , Mn2+ , Zn2+ , Ni2+ , Cu2+ , Ba2+ , Cd2+ or Ca2+ . The binding constant ( K SV ) and detection limit were also determined.