Facile green synthesis of multifunctional carbon dots from cassava peel for heavy metal ion sensing, photocatalytic degradation, antioxidant activity, and fluorescence bioimaging

Cassava (Manihot esculenta) is an economically significant crop, and its by-product, cassava peels, presents a sustainable opportunity for creating high-value nanomaterials. Therefore, this work focuses on developing multifunctional carbon dots (CDs) from cassava peels using a green hydrothermal method. The CDs exhibited remarkable photophysical properties, including excellent fluorescence emission, high biocompatibility, and antioxidant activity. These CDs were utilized as fluorescent sensors for detecting heavy metal ions (Fe³⁺ and Hg²⁺) in real water samples, achieving detection limits of 68.0 and 23.9 μM, for Fe³⁺ and Hg²⁺, respectively. Additionally, CDs demonstrated efficient photocatalytic degradation of methylene blue (72%) under various light sources and also showed strong antioxidant activity, with 82% scavenging inhibition at 10.0 mg/mL concentration. CDs also exhibited no cytotoxicity and were then applied for fluorescence bioimaging in HeLa cells. The as-synthesized CDs made from natural sources like cassava could be further appropriate for use in bioimaging and biosensing.