Lignin nanoparticles: The next green nanoreinforcer with wide opportunity

Lignocellulosic biomass is one of the most promising carbon-containing sources, which has vast potential in various fields. Lignin, as the second-highest constituent in lignocellulosic biomass after cellulose, is an underutilized source due to lesser knowledge on its full potential other than using it as a fuel source. The applications of lignin can be further enhanced when the size of lignin is reduced to nanoscale where the surface area and the properties of lignin are improved. Herein, we reviewed the nanoscale lignin, or lignin nanoparticles (LNP) prepared via facile methods, which can lead to the controllable synthesis of LNP at reduced reaction time and chemical consumption. Furthermore, its applications as nanoreinforcer that can enhance the antibacterial, antiradical, UV protectant, emulsion stabilization and catalysis reaction properties of various nanomaterials were discussed. Additionally, the new potential area on the application of catalysis has been highlighted. This review may inspire future research on LNP dedicated to the highlighted research areas.