Obtaining lignin nanoparticles by sonication

•The paper present a physical method to obtain nanoparticles based on lignin.•The nanoparticles were characterized from morphological and dimensional point of view.•The modified lignin where characterized by FTIR, GPC, QQ-HSQC and 31P-NMR.•Main reaction patterns: depolymerization and oxidative coupling/polymerization. Lignin, the main natural aromatic polymer was always aroused researchers interest. Currently around 90% of this biomaterial is burned for energy. It has a very complex and complicated structure which depends on the separation method and plant species, what determine difficulties to use as a raw material widely. This research presents a physical method to modify lignin by ultrasonic irradiation in order to obtain nanoparticles. The nanoparticles synthesized were dimensionally and morphologically characterized. At the same time the preoccupations were to determine the structural and compositional changes that occurred after sonication. To achieve this, two types of commercial lignins (wheat straw and Sarkanda grass) were used and the modifications were analyzed by FTIR-spectroscopy, GPC-chromatography, 31P-NMR-spectroscopy and HSQC0. The results confirm that the compositional and structural changes of nanoparticles obtained are not significantly modified at the intensity applied but depend on the nature of lignin.