Sustainable synthesis of lignin-derived carbon dots with visible pH response for Fe3+ detection and bioimaging

• Published in: Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy Molecular and biomolecular spectroscopy, 2023-12, Vol.302, p.123111, Article 123111
• Main Authors: Lin, Simin, Lai, Chunmei, Huang, Zejie, Liu, Wei, Xiong, Lei, Wu, Yuxin, Jin, Yanqiao
• Format: Article
• Language: English
• Subjects: Bioimaging; Carbon dots; Enzymatic hydrolysis lignin; Fe3+ detection
• ISSN: 1386-1425
• DOI: 10.1016/j.saa.2023.123111

[Display omitted] •The quantum yield of LCDs was significantly improved to 45.05%.•Quenching of LCDs by Fe3+ is based on the formation of non-fluorescent complexes.•LCDs have visualized pH-sensitive responses with different luminescent colors in acid/alkali environments.•The favorable low toxicity and biocompatibility of LCDs enable them to enter HepG2 cells through endocytosis. Synthesis of lignin-based carbon dots (LCDs) with high quantum yield (QY), stable fluorescence properties and biocompatibility has been a challenge. Here, we propose an improved two-step strategy for producing high-quality LCDs from enzymatic hydrolysis lignin (EHL). The p-aminobenzenesulfonic acid used in the strategy not only provides nitrogen and sulfur elements, but also tailors the disordered three-dimensional structure of EHL. The successful co-doping of N and S elements favors the reduction of the optical energy bandgap (Eg), resulting in a high QY of 45.05% for LCDs. The LCDs exhibited superior selectivity and sensitivity for Fe3+ with a limit of detection (LOD) of 0.15 μM when Fe3+ concentration was 50–500 μM. In addition, LCDs demonstrated significant fluorescence in HepG2 cells and HepG2 cells loaded with LCDs at a concentration of 80 μg/mL showed good viability, suggesting that they are suitable for in vivo applications. The luminescent centers of LCDs change during pH regulation and thus show a special visual response to pH changes, making them have great potential for detecting metabolism in living cells. This work provides a novel and low-cost method for fabricating sustainable fluorescent probes for chemical sensing and bioimaging.