• Green synthesis of carbon dots from biomass offers a sustainable route for nanomaterial production, addressing waste valorization and environmental footprint.
• Functionalized carbon dots serve as efficient photocatalysts for degradation of organic pollutants and CO2 reduction, contributing to environmental remediation.
• In renewable energy, carbon dots enhance light-harvesting in solar cells and dye-sensitized solar cells, improving energy conversion efficiency.
• Challenges remain in controlling size, uniformity, and quantum yield scalability, necessitating further research on structure-activity relationships for commercial deployment.