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

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 highquality 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 & mu;M when Fe3+ concentration was 50-500 & mu;M. In addition, LCDs demonstrated significant fluorescence in HepG2 cells and HepG2 cells loaded with LCDs at a concentration of 80 & mu;g/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.

Automated summary

A improved two-step strategy is proposed to synthesize high-quality lignin-based carbon dots (LCDs) with high quantum yield and stable fluorescence properties. The successful co-doping of nitrogen and sulfur elements leads to a high quantum yield of 45.05% for the LCDs. Additionally, the LCDs exhibit superior selectivity and sensitivity for Fe3+ and have potential applications in chemical sensing and bioimaging.