Facile Synthesis of N-Doped CDs from Ridge Gourd Seeds for the Sensitive Detection of Fe Ions.

This study reports the synthesis of nitrogen-doped carbon dots (N-CDs) from ridge gourd seeds via a hydrothermal process. The optical and physicochemical properties of the synthesized N-CDs were characterized using various techniques, including UV-Visible, fluorescence (FL), FT-IR, X-ray diffractometer (XRD), TEM, and XPS. The resulting N-CDs had an average size of 4.72 ± 0.2 nm, high monodispersity, and a quantum yield of 11.8%, which is related to efficient light emission. These N-CDs were highly dispersible in water and exhibited excitation-independent FL at varying excitation wavelengths. They showed excellent stability under diverse conditions, such as variations in pH, high ionic strengths, and prolonged light exposure, which enhances their use in potential applications. As FL probes, the N-CDs demonstrated the selective and sensitive detection of Fe ions, with a significant FL quenching response. A strong linear correlation (R = 0.9899) was observed for Fe concentrations in the range of 0-20 µM, with a detection limit of 67.3 nM. Notably, the FL quenching could be reversed by adding EDTA, which is a chelating agent for Fe, indicating the potential for reversible sensing applications. The biocompatibility of the N-CDs was assessed via an MTT assay on HCT 116 cells, which revealed low cytotoxicity (94.3 ± 1.8% viability at 75 µg/mL). These findings suggest that N-CDs are safe for in biological applications and hold great promise for use in biosensing, bioimaging, and environmental monitoring.