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 Hg, while nearly no intensity changes were observed when in the presence of Na, Mg, Mn, Zn, Ni, Cu, Ba, Cd or Ca. The binding constant () and detection limit were also determined.