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Diethylenetriamine-β-cyclodextrin (3N-β-CD)-modified carbon quantum dots were synthesized for the first time via a one-step hydrothermal method using citric acid as the carbon source and diethylenetriamine-β-cyclodextrin as the nitrogen source. The synthesized carbon quantum dots were used as fluorescent probes for the selective detection of Hg2+ and Fe3+ in an aqueous solution and live cell imaging application on Hela cancer cell line. [Display omitted] • 3 N -CQDs were synthesized readily using citric acid as the carbon source by hydrothermal method. • The 3 N -CQDs showed a favorable fluorescence performance towards Hg2+ and Fe3+ detection. • Cytotoxicity assay indicated that the 3 N -CQDs had extremely low cytotoxicity. • The 3 N -CQDs showed good biocompatibility and bioimaging property in the cell imaging. Diethylenetriamine-β-cyclodextrin-modified carbon quantum dots (3 N -CQDs) were synthesized via a one-step hydrothermal method using citric acid as the carbon source and diethylenetriamine-β-cyclodextrin (3 N-β-CD) as the nitrogen source. The successful preparation of 3 N -CQDs were revealed by infrared absorption spectroscopy, ultraviolet (UV)-visible absorption spectroscopy, fluorescence spectroscopy, XRD, XPS, TEM, and TG. Further spectroscopic studies showed that the synthesized carbon quantum dots offered good anti-interference capability. The relative fluorescence quantum yield was 67.2 %. The limits of detection for Hg2+ and Fe3+ were 0.25 µM and 0.57 μM, respectively. Cytotoxicity and imaging studies showed that the prepared carbon quantum dots had low cytotoxicity, good biocompatibility, and good cellular imaging capability for HeLa cells. They offered fluorescent sensing of Hg2+ and Fe3+ in live cells. Therefore, 3 N -CQDs were ideal fluorescent probes for the detection of Hg2+ and Fe3+ in water. [ABSTRACT FROM AUTHOR]

• His-GQDs synthesized via pyrolysis green-synthesis route. • His-GQDs were used for cellular imaging of ACHN cell lines as a novel bright green fluorescence probe. • This is the first reported of label-free, selective and non-toxic fluorescence probe for cellular imaging of ACHN cell lines. • Cellular imaging was achieved successfully show that His-GQDs can be easily penetrated into cytoplasm. In this study, bright green-luminescent probe (His-GQDs) were synthesized using a new one-pot "bottom-up" pyrolysis green-synthesis route, without consuming any water and chemical reagent. Citric acid as carbon source and Histidine as amino-functionalized agent, with optimized ratios, were used for fabricating His-GQDs as a novel, label-free, and selective probe. His-GQDs can be then used for cellular imaging of human ACHN cell lines that are composed of graphene sheets with the average size of 2.0 nm. Obtained His-GQDs probe has ultra-small size, low toxicity, chemical stability, biocompatibility, anti-photo bleaching and excellent optical properties with a rather high quantum yield of 62.8%. The detailed structural studies were confirmed by FT-IR, HR-TEM and powdered X-ray diffraction analysis respectively. In this project, the His-GQDs were utilized for cellular imaging of human ACHN cell lines for the first time. This probe indicated the presence desired biocompatibility of His-GQDs in human ACHN cell lines even at high their concentration (1800 µg mL−1) at 24 h post-treatment and their distribution in ACHN cell lines cytoplasm. [ABSTRACT FROM AUTHOR]