Sulfite Lignin Nanoparticles and Nanovesicles as Biologically Active Crop Growth Stimulants

Sulfite lignin or lignosulfonate is a large-scale by product of pulp and paper mills. Features of the chemical structure of lignosulfonates in combination with their biocompatibility, biodegradability, environmental safety, and an unlimitedly reproducible raw material base open up wide opportunities for the practical application of materials based thereon. Of particular interest is the production of nanoparticles and other lignosulfonate-containing nanostructures. Compared to the original lignosulfonates, they acquire additional valuable properties due to their small size, increased surface area, and quantum size effects. In this work, water dispersions of nanoparticles and air-dry nanopowders of various morphologies (nanoparticles, nanovesicles, and nanorods) were prepared on the basis of lignosulfonates. It has been established that the formation of lignosulfonate-containing nanostructures proceeds through various noncovalent interactions in aqueous and mixed water–organic media. A special role is played by electrostatic effects caused by the polyelectrolyte nature of lignosulfonates. The size, charge (ζ-potential), and morphology of the obtained nanostructures depend on and are controlled by the composition of lignosulfonates (Mw 9250–46,300 Da), type (EtOH/Ac) and concentration (φEtOH/Ac = 0.60–73.0 vol %) of the organic phase, as well as the method of formation (on the surface of an organic liquid/in the bulk of a lignosulfonate solution) of nanostructures. The growth-stimulating activity of the nanoparticles obtained is shown, which makes it possible to recommend our lignosulfonate-containing nanomaterials as biologically active growth stimulators of agricultural crops (by the example of radish (Raphanus sativus) and watercress (Lepidium sativum)).