Carbon dot-functionalized cellulosic fibers from ficus benghalensis: a step towards sustainable structural and functional materials

The development of sustainable functional materials from renewable resources has attracted increasing interest for advanced bio interface and composite applications. In this study, carbon dot (CD)-functionalized Ficus benghalensis aerial root fibers were fabricated through a simple dip-assisted surface modification strategy to impart optical and antibacterial functionalities while preserving the inherent mechanical integrity of natural cellulosic fibers. X-ray diffraction and Fourier transform infrared spectroscopy confirmed the successful immobilization of carbon dots and oxygen-containing functional groups without disrupting the semi-crystalline fiber architecture. The functionalized fibers exhibited a tensile strength of 161.23 MPa with a strain of 0.054, indicating good mechanical performance. Ultraviolet absorption in the 220–280 nm region and broad photoluminescence emission from 390–700 nm with a maximum intensity of 3495 a.u. at 530–535 nm verified the successful incorporation of fluorescent carbon dots. The coated fibers also demonstrated antibacterial activity against Escherichia coli and Staphylococcus aureus, producing inhibition zones of 19 and 17 mm, respectively, while confocal laser scanning microscopy confirmed reduced bacterial adhesion and biofilm formation. These findings demonstrate that Ficus benghalensis fibers can be effectively functionalized with carbon dots to produce sustainable cellulosic materials with structural, optical, and antibacterial properties, making them promising candidates for antibacterial surface coatings, bio interface materials, fluorescence-based sensing platforms, and reinforcement in sustainable polymer composites.