Green carbon dots with multifaceted applications– Waste to wealth strategy

Carbon dots (CDs), a novel member of the carbon family, are recently emerging as a potential substitute for traditional fluorescent materials. Compared to chemically derived CDs, green CDs produced from the renewable resources drawn much attention owing to their distinctive features such as cost effective, non-toxic nature, tunable luminescence, improved aqueous solubility and high biocompatibility. Using sustainable raw material and biomass for the development of functional material promotes the minimization of waste production. In this review, we outline and briefly discuss various synthesis routes, fluorescent mechanisms and precursors required to form the CDs, with a primary emphasis on the eco-friendly hydrothermal approach. Different heteroatoms in the form of functional groups available on the surface of green CDs help improve their quantum yield, physicochemical, and optical properties without surface passivation. Moreover, CDs tunable and up- photoluminescence behavior (PL) led to their remarkable usage in sensing, drug delivery, and bioimaging. Further, the importance of food wastes (animal, plant, and food processing byproducts) as the source of carbon which is often overlooked, is also reported herein. The promising applications of CDs in bioimaging, fluorescent inks, drug delivery, catalysis, and heavy metal ions detection were also elaborated. In the end, an outlook on the opportunities, possible challenges, and appealing prospects concerning the beneficial exploitation of renewable resources are discussed.