Sustainable carbon dots from starch: Synthesis, properties, and emerging applications

Starch-based carbon dots (SCDs) have emerged as a versatile class of nanomaterials, combining the renewable and biodegradable nature of starch with the unique photoluminescent properties of carbon dots (CDs). This mini review provides a comprehensive overview of recent advances in the synthesis, structural understanding, optical behavior, and emerging applications of SCDs and their composite materials. Various synthesis methods—including hydrothermal treatment, microwave-assisted methods, and solvent-free pyrolysis—are discussed, emphasizing how processing conditions, precursor types, and dopants influence the physicochemical and photoluminescent properties of the resulting nanostructures. The multilevel structure of starch, including its granular morphology, amylose-amylopectin architecture, and semi-crystalline nature, is analyzed for its impact on SCD formation. Photoluminescence in these materials is attributed to core-state emission and surface defect states, often enhanced by heteroatom doping with nitrogen, phosphorus, or sulfur. Applications of SCDs are explored, including biosensing, ion detection, food packaging, bioimaging, and environmental remediation. Special attention is given to starch-CD composite systems such as films, hydrogels, and aerogels, which demonstrate improved mechanical performance, antioxidant activity, and smart functionalities. Finally, current limitations and future research directions are discussed, including strategies to enhance quantum yield, scalability, and targeted functionality, making SCDs a promising platform for sustainable nanotechnology.