Stabilized Lignin Nanoparticles for Versatile Hybrid and Functional Nanomaterials

Spherical lignin nanopartides are emerging biobased nanomaterials, but instability and dissolution in organic solvents and aqueous alkali restrict their applicability. Here, we report the synthesis of hydroxymethylated lignin nanopartides and their hydrothermal curing to stabilize the particles by internal cross-linking reactions. These colloidally stable particles contain a high biobased content of 97% with a tunable particle size distribution and structural stability in aqueous media (pH 3 to 12) and organic solvents such as acetone, ethanol, dimethylformamide, and tetrahydrofuran. We demonstrate that the free phenolic hydroxyl groups that are preserved in the cured particles function as efficient reducing sites for silver ions, giving rise to hybrid lignin-silver nanopartides that can be used for quick and facile sensing of hydrogen peroxide. The stabilized lignin particles can also be directly modified using base-catalyzed reactions such as the ring-opening of cationic epoxides that render the particles with pH-dependent agglomeration and redispersion properties. Combining scalable synthesis, solvent stability, and reusability, this new class of lignin nanopartides shows potential for its use in circular biobased nanomaterials.

Automated summary

This study reports the synthesis of stable lignin nanoparticles and explores their potential applications. The nanoparticles have a high biobased content and exhibit structural stability in different environments. They can also be modified by various reactions to expand their applicability.