Green synthesis of elephant manure-derived carbon dots and multifunctional applications: Metal sensing, antioxidant, and rice plant promotion

Carbon dots, the carbon nanomaterials, have been greatly developed for several applications including fluorescent sensors for metal ion detection, antioxidant activity, and plant growth promotion due to their excellent photophysical properties, non-toxicity, and high quantum yield. Therefore, this research focused on the synthesis of multifunctional carbon dots from elephant manure via green hydrothermal synthesis owing to its chemical composition of cellulose, hemicellulose, and lignin. The as-synthesized carbon dots exhibited blue fluorescence emission under UV light and the excitation wavelength-dependent fluorescence enhancement. Carbon dots could be further used as a "turn-off" fluorescence sensor for Hg2+ detection as a part of environmental monitoring. Furthermore, the as-synthesized carbon dots containing high phenolic content showed the antioxidant activity and promoted rice growth with an increase in the characteristic aroma compound (2-acetyl-1-pyrroline), confirmed by GC–MS analysis.