Betel-derived nitrogen-doped multicolor carbon dots for environmental and biological applications

An innovative, facile, low-cost and one-pot hydrothermal carbonization method was developed for the synthesis of bright fluorescence nitrogen-doped carbon dots (NCDs) using Piper betle (Betel) leaf as a carbon and nitrogen precursor. Various advanced physicochemical characterization techniques have been performed to confirm the structural and optical properties of the resulting Betel-derived NCDs (B-NCDs). The as-synthesized B-NCDs exhibited unique excitation-dependent fluorescence behavior, high fluorescence/photochemical stability, exceptional solubility in hydrophilic solvents like water, and good biocompatibility. On the basis of the astounding optical behavior of B-NCDs, they were utilized as a nanoprobe for determination of Fe3+ ion by the fluorometric method. Notably, this nanoprobe was performed by a linear relationship between the fluorescence intensity and the concentration of Fe3+ ion ranging from 5 to 30 μM with a detection limit as 0.43 μM. Highly selective and sensitive determination of Fe3+ ion was carried out through the fluorescence quenching of B-NCDs due to the resonance energy/electron transfer (RET) mechanism. Besides, the resulting B-NCDs employed as a biocompatible probe in multicolor imaging applications of HCT-116 human colon cancer cells. B-NCDs is not only efficient nanosensor for the determination of Fe3+ ion and biocompatible probe for the multicolor imaging. It also would be a substantial alternative for the traditional fluorescent inks due to its extraordinary fluorescence stability, biocompatibility, pollution-free, and easily washable. In this report for the first time, Betel leaf as carbon and nitrogen source was used to synthesize B-NCDs without adding any chemical reagent. Thus it was applied for diverse analysis field.