Nitrogen-doped carbon dots as a fluorescent probe for the highly sensitive detection of Ag+ and cell imaging.

An easy hydrothermal synthesis strategy was applied to synthesize green-yellow emitting nitrogen-doped carbon dots (N-CDs) using 1,2-diaminobenzene as the carbon source, and dicyandiamide as the dopant. The nitrogen-doped CDs resulted in improvement in the electronic characteristics and surface chemical activities. N-CDs exhibited bright fluorescence emission and could response to Ag+ selectively and sensitively. Other ions produced nearly no interference. A N-CDs based fluorescent probe was then applied to sensitively determine Ag+ with a detection limit of 5 × 10-8  mol/L. The method was applied to the determination of Ag+ dissolved in water. Finally, negligibly cytotoxic, excellently biocompatibile, and highly fluorescent carbon dots were applied for HepG2 cell imaging and the quenched fluorescence by adding Ag+ , which indicated its potential applications.