High photoluminescent nitrogen-doped carbon dots with unique double wavelength fluorescence emission for cell imaging

High photoluminescent (PL) nitrogen-doped carbon dots (N-CDs) have been synthesized using ferric ammonium citrate (FAC) and urea as raw materials by simple one-pot hydrothermal process. The N-CDs possess bright blue fluorescence (centred at 450 nm; 36.2% quantum yield) and green fluorescence (centred at 530 nm; 47.6% quantum yield) only by adjusting the excitation wavelength from 310 nm to 510 nm. The N-CDs exhibited high N content of 32.81 wt%, low cytotoxicity, and good PL stability at different pH values, ion strengths and temperature, respectively. As-prepared N-CDs were explored for cell imaging with great biocompatibility. The remarkable properties of N-CDs indicated their potential toward sensing and biological applications.