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 (KSV) and detection limit were also determined.