Lignocellulosic biomass-derived carbon quantum dots (CQDs): A novel approach utilizing organosolv lignin from Moso bamboo waste

Converting lignocellulosic materials to carbon quantum dots (CQDs) has garnered significant interest to transform biomass wastes into highly valuable products. We chose to use lignin as our feedstock because high-value products more readily utilize cellulose and hemicellulose. Lignin, arguably the most underutilized and complex biopolymer within any biomass, presents an appealing yet overlooked opportunity. While some may argue that lignin-based CQDs are no longer groundbreaking, this is because existing studies typically rely on commercially available lignin, ignoring biomass-derived sources. Therefore, in our pioneering research, we utilized organosolv lignin, prized for its structural purity and extracted from Moso bamboo waste, as the carbon source in a facile two-step technique to synthesize luminous CQDs. The process involved the addition of 2,4-diaminobenzenesulfonic acid, a mild-organic acid that acted as a source for both nitrogen (N) and sulphur (S). A 12-h hydrothermal treatment at 200 °C with 0.1 M of acid addition attained the best result. The resultant CQDs display strong green fluorescence, with the highest quantum yield of 17.7% seen in N and S co-doped CQDs. With their obvious and specific fluorescence quenching impact on Fe3+, CQDs demonstrate great potential as a fluorescent nanoprobe for metal ion detection. This CQD nanoprobe responds very sensitively to Fe3+ between 0 and 500 μM (R2 = 0.9803), with a detection limit of 0.15 μM. This research not only presents a unique alternative nanoprobe for the sensing field using renewable biomass lignin, but it also paves the way for the long-term, cost-effective, and scalable manufacturing of CQDs.