Syntheses of N-Doped Carbon Quantum Dots (NCQDs) from Bioderived Precursors: A Timely Update

The emergence of carbon quantum dots (CQDs) opens up new opportunities in different branches of science and technology primarily because of their conducive biocompatibility, tunable bandgaps, and unique optoelectronic properties, namely, photoluminescence (PL) and fluorescence. Although CQDs are given precedence in the literature, the large-scale sustainable synthesis and the purification of CQDs as well as the study of their effects on health and environment remain a challenge. Hence, more sustainable approaches are being developed to make this category of materials widely applicable, specifically in the context of replacing toxic metal-based QDs. Among the reported synthetic protocols employed to prepare CQDs while controlling their properties, the incorporation of various dopants, surface functionalities, and defects into CQDs offers great promises. Amongst the possibilities, nitrogen dopants contribute significantly due to their broader precursor scope, natural abundance in sustainable bioderived resources, and relatively straightforward and inexpensive synthetic protocols, leading to assorted combinations of nitrogen (N)-doped carbon quantum dots (NCQDs). Here, a brief survey is presented on the recent developments of strategies deployed for the preparation of bioderived NCQDs, emphasizing the uniqueness of the synthetic methodology, choice of precursors, and purification strategies. In addition, characterization, properties, and applications of the selected NCQDs are highlighted. The present status and challenges are also discussed along with the future directions.