Facile synthesis of highly graphitized nitrogen-doped carbon dots and carbon sheets with solid-state white-light emission

•High graphitized carbon sheets were synthesized by facile hydrothermal method.•The formation and N-doping of carbon sheets were one-step obtained.•Under UV excitation, nitrogen-doped carbon dots exhibit direct white emission.•We develop a facile approach to resist self-quenching of NCDs in solid state.