Preparation of nanoparticles from hydroxymethylated lignin: Colloidal nanoparticles from hydroxymethylated lignin were prepared following a literature method. Briefly, 0.5 g of dry hydroxymethylated lignin was dissolved in a solvent mixture of 30 g of acetone and 10 g of deionized water with stirring for three hours at room temperature. The solution was vacuum filtered to pass a 0.45 μm pore size glass fiber filter to remove any insoluble solids. Finally, 120 g of water was added to the stirring solution to form the colloidal dispersion of hydroxymethylated lignin. Acetone was removed using a rotary evaporator under reduced pressure at 40 °C.