Green synthesis of coconut coir-based carbon dots for efficient detection of ferric ions

Iron (Fe) is an essential micronutrient for metabolic and physiological processes. Its dysregulation is associated with disorders such as Alzheimer's and hemochromatosis. Therefore, the development of cost-effective and selective probes for Fe(iii) detection is of significant clinical importance. In this study, fluorescent carbon dots derived from coconut coir (CCDs) were synthesized via a single-step hydrothermal method. The CCDs exhibited strong blue emission at 450 nm under 350 nm excitation and demonstrated selective fluorescence quenching in the presence of Fe(iii) ions, with a detection limit of 223.2 μM. HR-TEM revealed the particle size of CCDs ranged between 5.64 to 10 nm. XRD confirmed the crystalline nature. FTIR spectra indicated presence of hydroxyl and carboxyl groups contributing to dispersibility and surface passivation. Raman spectroscopy showed distinct D (1354 cm^-1) and G (1582.61 cm^-1) bands, characteristic of low-dimensional carbon nanostructures. Bioimaging and cytocompatibility studies in L929 fibroblast cells confirmed biocompatibility up to 500 μg mL^-1. Collectively, these findings highlight the potential of CCDs as an effective fluorescent probe for Fe(iii) sensing and bioimaging applications in medical diagnostics. The CCDs were cytocompatible at concentrations up to 500 μg mL^-1.