Crosslinking of hydroxymethylated lignin nanoparticles using hydrothermal process: 20 ml of HLNP colloidal dispersion (5 g L -1 ) was hydrothermally cured in a 40 ml Teflonsealed reactor at 150 °C overnight, please note that Teflon reactors should be clean from any dust or dirt particles to avoid interparticle cross-linking and aggregation during the hydrothermal curing step.