Orange-emitting N-doped carbon dots as fluorescent and colorimetric dual-mode probes for nitrite detection and cellular imaging.

Novel orange-emitting N-doped carbon dots (N-CDs) were prepared as fluorescent and colorimetric dual-mode probes for sensing nitrite (NO2-). The obtained N-CDs possessed fantastic optical properties and specific responses to NO2-. NO2- could induce the fluorescence static quenching of N-CDs, and a linear relationship was obtained in the range from 2 to 60 μM with the detection limit of 0.35 μM. More interestingly, the N-CDs exhibited ratiometric absorption signals with visible color conversion (red-purple), which allowed the development of a simple colorimetric method for NO2- monitoring in the linear range of 2-80 μM with a detection limit down to 0.13 μM. Additionally, the N-CDs were capable of monitoring NO2- in the A549 cells, which indicated their great potential in biosensing.