Intense multi-state visible absorption and full-color luminescence of nitrogen-doped carbon quantum dots for blue-light-excitable solid-state-lighting

Currently, the excitation-wavelength-dependent photoluminescence of traditional carbon dots does not constitute true tuning and their absorptions show gradual attenuation in the visible region. Herein, we report a facile strategy to realize intense visible absorption and full-color emissions of nitrogen doped carbon dots via the control of surface nitriding. The quantum yields of the carbon dots in aqueous solution reached 49.2%, 30.6% and 30.3% for blue, yellow and red emissions, respectively. Structural characterizations and spectroscopic analyses verify that three diverse emitting states, i.e., sp(2) carbon core, C = O and C = N related surface defects, are responsible for the multi-state absorptions and tunable emissions of the carbon dots. The ability to truly tune luminescence into the red wavelength region with strong visible absorption enables these carbon dots to improve the correlated color temperature and color rendering index of traditional phosphor-converted white light-emitting diodes.