Biomimetic spherical silica production using phosphatidylcholine and soy lecithin

Abstract

Spherical silica particles are traditionally made via Stöber and modified-Stöber processes, which commonly use environmental toxins as reagents. Here we report a process to synthesise spherical silica particles using environmentally friendly biomolecules (phosphatidylcholine and soy lecithin) and employing water and soybean oil as solvents, rather than potentially harmful organic solvents. This scalable method represents an important step towards sustainable industrial silica syntheses. Under mildly acidic conditions phosphatidylcholine and soy lecithin can control the condensation of sodium silicate to form discrete, spherical silica particles. Silica particles with diameters ranging between 329 and 2232 nm were readily produced using phosphatidylcholine as the templating agent and soybean oil as the solvent in the presence of sodium silicate. Narrower size distributions (262–1272 nm) were achieved using soy lecithin as the templating agent in an aqueous acetate buffer solution containing sodium silicate. Silica particles grown using low concentrations of phosphatidylcholine and soy lecithin as templating agents formed by a combination of coalescence and Ostwald ripening, whilst particles grown at high concentrations predominantly formed through Ostwald ripening behaviour. The possibility of sustainably producing spherical silica particles in a simple biomolecule-templated synthesis is shown.