Advancements in the green synthesis of carbon dots for sustainable development

The use of various biomass derivatives and wastes to produce carbon dots (CDs) represents a green synthesis approach that holds great potential for commercialization by offering economically viable, abundant, and sustainable resources. The process is reliable and reproducible by producing high-quality CDs with controllable size and surface structure, high photoluminescence (PL), and narrow emission. This review highlights the potential of biomass wastes and derivatives as a valuable resource for the production of CDs, showcasing their economic viability and environmental sustainability. The discussion is focusing on optimizing the green synthesis of CDs from different biomass precursors, including small molecules (e.g., sugars, polymers, amino acids, proteins, etc.) and biomass wastes (e.g., leaves, stem, root, flower, pollen, etc.), elucidating the underlying synthetic mechanisms, and exploring various modification techniques. The pursuit of high-quality CDs materials is also realized through innovative modification strategies, such as surface passivation, precise morphology and size control, and heteroatom doping, which enable tailoring the properties of CDs according to specific requirements while minimizing waste generation. The formation mechanism and tuning of optical properties were also discussed in detail, focusing on the comparison with CDs using other precursors. We further introduced the sustainable applications of these green CDs on renewable energies, such as photocatalysis, electrocatalysis, supercapacitors, lithium-ion batteries, and photovoltaics. Finally, this review provides a perspective on the challenges, potential advancements and future directions in the field of the green CDs.