Synthesis of blue-sparkling N, S-doped carbon dots for effective detection of nitro explosive and Fe3+ ion and anti-counterfeiting studies

Highly blue-luminescent nitrogen & sulfur-doped carbon dots (N, S-CDs) made with homocysteine and ethylene diamine by simple single-step microwave-assisted style. The prepared carbon dots showed a higher photoluminescent quantum yield (PL-QY), which is found to be 45 %. FTIR and XPS analysis reveals that these N, S-CDs contain rich nitrogen, and sulfur as well as C=O and C=C functional groups. N, S-CDs had a mean size around 3-4 nm, very interestingly, obtained carbon dots exhibit excitation-dependent photoluminescent character, are water-soluble, and restore luminescent stability under UV-light exposure and a wide range of pH. The crafted N, S-CDs are hired for precise and discriminating detection of multiple water impurities such as Fe³⁺ ion and Picric acid. The complexation between oxygen species of N, S doped CDs, and Fe³⁺ ion follows the inner-filteration effect (IFE) and with Picric acid follows Forster Resonance Energy Transfer (FRET) for the doped N, S-CDs are found to be the utmost possible mechanism for the observed sensing performance. The lower detection limit (LOD) of Fe³⁺ sensors is about 0.11 µM and for picric acid is 0.07 µM. Moreover, these blue-emissive N, S-CDs as competent fluorescence sensors, have been used as fluorescent inks, as well as in advanced portable devices information security and filter paper-based probes for visual recognition might also hold prominent ability to make wider applications in biological systems.