Fe³⁺ detection, bioimaging, and patterning based on bright blue-fluorescent N-doped carbon dots

Bright blue fluorescent N-doped carbon dots (N-CDs) with satisfactory yield (54%) were successfully fabricated by one-step hydrothermal treatment of astragalus. The obtained N-CDs possessed superior stability, solubility and high resistance to photo bleaching, and can be used as label-free nanosensors for the determination of Fe³⁺. The quantitative analysis of Fe³⁺ showed a linear range of 50 to 250 μM with the detection limit as low as 42 nM. Moreover, the as-prepared N-CDs have been used in cellular imaging owing to their distinct merits of simplicity, convenience, fast response and good selectivity towards Fe³⁺. Besides, the N-CDs could also be further used as fluorescent inks for drawing luminescent patterns.