Comparative study for N and S doped carbon dots: Synthesis, characterization and applications for Fe3+ probe and cellular imaging

• A facile and eco-friendly approach to prepare N or S-doped carbon dots by microwave method.
• Comparative study about N and S doped effects on CDs' morphology, chemical structures and optical properties.
• A highly sensitive N-CDs fluorescence probe for detection of Fe3+.
• Multicolor cell imaging and detecting Fe3+ in bio-system by N-CDs.

A facile and eco-friendly approach to prepare nitrogen(N)- and sulfur(S)-doped carbon dots (CDs) by one step microwave-assisted pyrolysis of the precursors with dl-malic acid as carbon source, ethanolamine and ethane-sulfonic acid as N and S dopants, respectively, was reported. Through the extensive investigation on morphology, chemical structures and optical properties of the carbon dots, it was found that the obtained CDs exhibited good luminescence stability, high resistance to photo bleaching and favorite solubility. Compared with undoped CDs, adding the N or S dopant could give rise to a slightly smaller particle size and a long fluorescence lifetime of CDs. Moreover, the optimal N-CDs was successfully employed as good multicolor cell imaging probes due to its fine dispersion in water, excitation-dependent emission, excellent biocompatibility and low toxicity. Besides, such N-CDs showed a wide detection range and excellent accuracy as fluorescent probe for Fe3+ ions. This probe enabled the selective detection of Fe3+ ions with a linear range of 6.0–200 μM and a limit of detection of 0.80 μM.

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