Proton-controlled synthesis of red-emitting carbon dots and application for hematin detection in human erythrocytes.

The Red-emitting nitrogen-doped carbon dots (N-CDs) are synthesized using o-phenylenediamine by a one-step method, and can serve as a fluorescent probe for "turn off" detection of hematin in human red cells. The red-emitting N-CDs can be obtained only in acidic conditions and the emission of the red-emitting N-CDs is pH-dependent, indicating proton-controlled synthesis and emission. The red-emitting N-CDs are 2.7 nm in mean size and have a uniform dispersion and exhibit a high quantum yield (12.8%) and great optical properties. The developed sensing system for hematin displays a linear response from 0.4 to 32 μM with a detection limit of 0.18 μM. Importantly, this fluorescent probe demonstrates a good potential practicability for the quantitative detection of hematin in complex matrixes. Graphical abstract ᅟ.