Self-assembly of kraft lignin into nanospheres in dioxane-water mixtures

Abstract

Kraft lignin (KL), a by-product in the pulping and papermaking industry, is an abundant, renewable resource. In this work, nanosphere formation of KL has been investigated via self-assembly induced by adding water to a KL/dioxane solution. The KL nanospheres were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), dynamic light scattering (dynLS) and static light scattering (statLS). It was found that the nanoparticles have uniform nanospherical morphologies, including a small hollow cavity space in the interior. The π-π interactions between the aromatic rings of KL are demonstrated to be an important driving force in the self-assembly process. The KL nanosphere sizes can vary by hundreds of nanometers depending upon the preparation conditions. These newly obtained KL nanospheres have the advantages of biocompatibility, biodegradability, low toxicity, easy preparation, and low cost. Thus KL nanospheres are attractive for applications in life science, medicine, biology, food science, and agriculture. This approach presented here is an economically feasible and facile strategy for the sustainable utilization of kraft lignin.

Lignin for Nano‐ and Microscaled Carrier Systems: Applications, Trends, and Challenges

“…The most common method for the preparation of LNPs involves solvent exchange by adding a non‐solvent into lignin solution, or vice versa, causing formation of spherical particles due to the minimization of surface energy (Figure a–c) . Aqueous and non‐aqueous solvents (THF, dioxane, dimethyl sulfoxide, acetone, and ethanol) have been used to dissolve lignin, with water being the most commonly used non‐solvent to produce spherical particles. In the case of ethanol–water solvent mixture, the particle diameter has been reported to controllably increase as the dilution rate decreases (Figure c) .…”

Lignin for polymer and nanoparticle production: Current status and challenges

“…Nanoparticles are then filtered from the system. When the solvent environment is changed in the mixture, nanoparticles are formed via self‐assembly of lignin molecules driven by forming van der Waals and π‐π interactions between the aromatic rings of lignin . Table summarizes the specifications of lignin‐based nanoparticles produced from different sources.…”

“…Due to their wide applicability and ease of use, a variety of solvent/lignin combinations have been evaluated to produce LNPs with different shapes and sizes (Table ). KL can form nanospheres via self‐assembly in a dioxane/water mixture, and the size of the LNPs can be controlled by the dropping speed of water in the mixture . Dioxane seems to impact the uniformity and structure of LNP .…”

“…KL can form nanospheres via self‐assembly in a dioxane/water mixture, and the size of the LNPs can be controlled by the dropping speed of water in the mixture . Dioxane seems to impact the uniformity and structure of LNP . Spherical LNPs were generated by dissolving softwood KL in THF and subsequently introducing water into the system through dialysis, which made nanoparticles with better dispersion performance compared with that generated via dropping method .…”

“…Ge et al also fabricated LNPs of lignosulphonates following these two alternative methods, which yielded LNPs with varied particle sizes. Li et al reported that spherical and hollow LNPs were obtained by using dioxane and ethanol as solvents in the solvent shifting precipitation of KL. Following the same method of solvent shifting, spherical and irregular shaped nanoparticles were produced by using OSL and KL, respectively …”