Waste derived approach towards wealthy fluorescent N-doped graphene quantum dots for cell imaging and H2O2 sensing applications

The present article is based on Synthesis of N-GQD by using waste material such as arjuna bark and melamine sponge, which is used for in vitro as well as in vivo cells imaging and H2O2 sensing in biological systems. [Display omitted] •Waste derived approach toward the synthesis of N-GQD.•Arjuna bark is used as carbon source and waste melamine sponge is used as nitrogen source.•Simple microwave treatment is used for the synthesis of N-GQD.•As synthesized N-GQD is used for cell imaging and H2O2 sensing. Herein, we report the synthesis of a highly fluorescent nitrogen doped graphene quantum dots (N-GQDs) from waste precursors such as melamine sponge and arjuna bark via a microwave treatment and its functional and morphological characterization using various spectroscopy techniques such as optical, FTIR, XPS and TEM. The as-prepared aqueous N-GQD (dia. 2–3 nm) was used for the bio-imaging application using breast carcinoma cell line (MDA-MB-231) as a model, and the locations of all cells in the cytoplasm as well as nuclei were observed to stain brightly in blue fluorescent color successfully. In addition to that, the aqueous N-GQD showed fluorescence quenching behavior in the presence of hydrogen peroxide, which was exploited to sense H2O2, a probable toxin generated in the diseased cells. Importantly, the cell cytotoxicity was measured and found to be non-toxic (70% survival) to the MDA-MB-231 cells even at very high concentration (∼1.8 mg/ml) of the synthesized N-GQD. This study revealing excellent biocompatibility and imaging of the model cancer cells, and sensing of H2O2 by fluorescent quenching, indicates potential in-vivo cell culture applications of the prepared fluorescent N-GQD.