Solvent-free synthesis of nitrogen doped carbon dots with dual emission and their biological and sensing applications

Carbon dots with dual emission have drown increasing attention in biology and medicine due to their fascinating optical and biological properties. Herein, dual emissive nitrogen-doped carbon dots (N-doped CDs) are synthesized by simple annealing of ammonium citrate in the air via solvent-free carbonization. Interestingly, N-doped CDs display dual emission peaking at 462 nm and 560 nm under excitation of 360 nm and 470 nm, respectively. The dual PL emission spectra of the N-doped CDs illustrate that each emission is associated with the single excitation band. The data reveals that two autonomous fluorescent centres are co-existed in N-doped CDs because doping with nitrogen (N) could change the surface chemistry of the CDs. In addition, dual emissive N-doped CDs have significantly low toxicity and could be applied as multicolor cell imaging using T-ca cancer cells. Moreover, obtained N-doped CDs are sensitive to temperature in the range of 15–90 °C and show potential to detect temperature in living cells. Furthermore, low toxicity and high biocompatibility proved that the obtained N-doped CDs could be applied in vivo imaging. Besides, the dual emissive N-doped CDs have the ability to probe Fe3+ ions in water as well as in living T-ca cells.