Facile and Efficient Synthesis of Silver Nanoparticles Based on Biorefinery Wood Lignin and Its Application as the Optical Sensor

Fabricating silver nanoparticles (AgNPs) based on renewable energy sources is wildly exploited because of the sustainable synthetic strategy and versatile applications of AgNPs. Alkali lignin (AL), as the byproduct from pulp mills, is a potential natural reducing agent. However, the synthetic methods of AL-based AgNPs (AL@Ag) still have drawbacks, such as unusual conditions and extra and high-cost purification processes. Here, a facile and efficient approach to synthesize and purify good-dispersing AL@Ag (17–27 nm) was presented, using Ag₂O as the silver precursor and AL as both reducing agents and stabilizers in dimethyl sulfoxide (DMSO) solvent. The maximum reduction capacity of AL to Ag⁺ was increased to 8 mM/g at room temperature because of the activation of both Ag₂O and DMSO. Most conveniently, the product was effectively purified by easy centrifugation. The reducing mechanism and reaction behavior were also systematically studied. Meanwhile, AL@Ag maintained versatile applications of AgNPs and exhibited great potential as the colorimetric sensor and plasmonic resonance energy acceptor for Hg²⁺ and rhodamine B, respectively. Our work displayed a general and efficient method to prepare AL@Ag, which might provide a realizable perspective to the high-value utilization of lignin

Fluorescent pH-Sensing Probe Based on Biorefinery Wood Lignosulfonate and Its Application in Human Cancer Cell Bioimaging

A water-soluble, ratiometric fluorescent pH probe, L-SRhB, was synthesized via grafting spirolactam Rhodamine B (SRhB) to lignosulfonate (LS). As the ring-opening product of L-SRhB, FL-SRhB was also prepared. The pH-response experiment indicated that L-SRhB showed a rapid response to pH changes from 4.60 to 6.20 with a p<i>K</i>_a of 5.35, which indicated that L-SRhB has the potential for pH detection of acidic organelle. In addition, the two probes were internalized successfully by living cells through the endocytosis pathway and could distinguish normal cells from cancer cells by different cell staining rates. In addition, L-SRhB showed obvious cytotoxicity to cancer cells, whereas it was nontoxic to normal cells in the same condition. L-SRhB might have potential in cancer therapy. L-SRhB might be a promising ratiometric fluorescent pH sensor and bioimaging dye for the recognition of cancer cells. The results also provided a new perspective to the high-value utilization of lignin