Sweet Corn (Zea mays L. var. rugosa) Derived Fluorescent Carbon Quantum Dots for Selective Detection of Hydrogen Sulfide and Bioimaging Applications

We report a green, simple, and facile fluorometric method for the detection of hydrogen sulfide (S2-) using bluish green carbon quantum dots (CQDs) derived from sweet corn (Zea mays L. var. rugosa) as carbon source. The optical properties of the CQDs were studied using UV-visible, PL spectra and lifetime measurements. High-resolution transmission electron microscopy (HR-TEM), atomic force microscope (AFM) and dynamic light scattering (DLS) were used for morphological studies. X-ray diffraction (XRD) technique was used for phase analysis. Zeta potential, Fourier transform infrared (FT-IR), Raman and X-ray photoelectron spectroscopy (XPS) were used to measure the charge and composition of QDs. The prepared CQDs having size less than 2.4 nm with bluish green emission at similar to 470 nm and showed excellent stability for more than 6 months in aqueous medium. The synthesized CQDs showed highly sensitive and selective detection of sulfide ions (S2-) in aqueous medium over other toxic metal ions and inorganic salts, and the detection limit was 8 nM in the linear range from 5 to 100 nM. The synthesized CQDs had excellent hemocompatibility as evidenced from the hemolytic assay (2.86 %) and ESR estimation (7.5 mm/h) on human RBCs. The cell viability of CQDs was evaluated on Vero and A549 cell line by MTT assay, which produced more than 90 % of cell viability in both cell lines at 250 mu g/mL concentration. Owing to their biocompatible nature, the synthesized CQDs were used as a fluorescent probe for in vitro bioimaging applications.