New insight into lignin aggregation guiding efficient synthesis and functionalization of a lignin nanosphere with excellent performance

Abstract

Understanding the molecular mechanism of lignin nanoparticle (LNP) formation will precisely instruct its functionalization, which is of importance for biomass valorization. Trial-and-error approaches for mechanistic research at the molecular level are extremely difficult and resource intensive. Here we have revealed that the intra-molecular interactions of lignin aromatic rings were the internal force driving the aggregation of lignin into LNPs by combining molecular simulation with experimental methods. A quantitative aromatic interaction correlated with the configuration distribution of lignin dimer and LNP yields was also developed for guiding the synthesis and functionalization of LNPs. A cellulose-derived solvent, γ-valerolactone (GVL), was then screened out to sustain lignin molecules’ intramolecular stacking (−5.54 kJ mol⁻¹) into a spherical nucleus for the growth of a uniform and stable lignin nanosphere during solvent shifting. With the assistance of the LNP formation mechanism, lignin could successfully stabilize in situ generated gold nanoparticles with excellent photothermal performance during the production of LNPs in a GVL/water solution. The newly proposed mechanism will provide an important theoretical basis for upgrading lignin to value-added biomaterials in a green and facile pathway.