Multifunctional fluorescent carbon dots derived from Bergera koenigii leaves for bioimaging and anti-counterfeiting applications

Background Sustainable biomass-to-multifunctional fluorescent carbon dots (CDs) with biocompatibility, photostability, and security-related optical properties are attractive for bioimaging and anti-counterfeiting technologies. However, developing such materials from renewable biomass through a simple and sustainable process remains challenging. Methods Fluorescent CDs were prepared from Bergera koenigii (curry) leaves through a simple hydrothermal carbonization approach, utilizing the naturally occurring phytoconstituents in the leaves as carbon and heteroatom precursors. The resulting curry leaf-derived carbon dots (CCDs) were systematically characterized using UV–Vis spectroscopy, photoluminescence spectroscopy, ATR-FTIR, X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). Their stability and cytocompatibility were subsequently assessed, along with their potential for cellular imaging and anti-counterfeiting applications. Significant findings The resulting CCDs exhibited excitation-dependent cyan-blue fluorescence, high photostability, and prolonged storage stability. Spectroscopic analyses revealed abundant oxygen- and nitrogen-containing surface functionalities, while TEM showed quasi-spherical nanoparticles with an average diameter of approximately 5 nm and a graphitic lattice spacing of 0.21 nm. The CCDs displayed low cytotoxicity toward HCT-116 human colon cancer cells and enabled effective fluorescence-based cellular imaging. In addition, their strong fluorescence under ultraviolet excitation allowed their application as invisible fluorescent ink for anti-counterfeiting. These findings demonstrate that curry leaves can serve as a renewable precursor for producing multifunctional fluorescent CCDs with potential in biomedical imaging and information-security applications.