Multicolor emitting N/S-doped carbon dots as a fluorescent probe for imaging pathogenic bacteria and human buccal epithelial cells

Carbon dots co-doped with nitrogen and sulfur (NSCDs) were obtained from thiourea and TAE (Tris-acetate-ethylenediamine) buffer using microwave assisted hydrothermal synthesis. The synergistic presence of nitrogen and sulfur as a dopant results in teasing fluorescence properties and a fluorescence quantum yield of 57%. An HR-TEM study showed the NSCDs to be monodispersed and seemingly spherical with an average hydrodynamic diameter of 3.6 +/- 0.88 nm. The NSCDs are nontoxic as proven by an MTT assay for cytotoxicity. The optical characterization was done by using UV-Vis absorption and fluorescence spectroscopy which revealed excitation wavelength-dependent multicolor emissions. The characterization of surface topology was done by using X-ray diffraction, FTIR, and X-ray photoelectron spectroscopy. The NSCDs were used to image various pathogenic bacteria (E. coli, Klebsiella, Pseudomonas & Staphylococcus) and human buccal epithelial cells by applying multicolor fluorometry.