Lignin-derived high-quality graphene quantum dots: Synthesis, mechanistic insights, and emerging applications

Lignin-based graphene quantum dots (L-GQDs), serving as a bridge between renewable biomass resources and functional carbon materials. This review begins with the molecular structure of lignin, exploring various synthesis methods for L-GQDs. The precise elucidation of precursor-structure-property relationships could optimize their performance through the quantitative regulation of lignin unit properties and enable controllable synthesis. We elaborate on the photoluminescence mechanisms and fluorescence modulation strategies of L-GQDs, covering aspects such as structural design, synthesis pathways, and photophysical property optimization. Additionally, the review discusses the application prospects of L-GQDs in biology, energy conversion, and optoelectronics, and highlights the importance of synergistically aligning synthesis strategies with practical on-demands application. We also prospected research paradigm should focus on in-situ unveiling of nucleation kinetics during L-GQDs formation, photoluminescence mechanism decoding, toxicity regulation to enable green, sustainable and multidisciplinary cutting-edge applications. This figure illustrates the transformation of renewable lignin structural motifs into lignin-derived graphene quantum dots (L-GQDs), emphasizing tailored green synthesis strategies, tunable photoluminescence behaviors, and their versatile applications in biomedical, optoelectronic, and environmental fields. • The synthetic strategy of highly crystalline lignin-derived GQDs (L-GQDs) with superior photoluminescence and flexible tunability. • Mechanistic insights into luminescence origin and up-conversion behavior. • The prospects on state-of-the-art application in biomedical and optoelectronic devices. • Outlook on future L-GQDs development: in-situ technique for understanding lignin-to-GQD transformation, toxicity assessment, and targeted synthesis for tailored applications.