Can sustainable, monodisperse, spherical silica be produced from biomolecules? A review

Spherical silica is a fundamentally important material with uses across a wide and diverse range of areas. However, the synthetic routes to producing spherical silica—typically Stöber processes—are inherently unsustainable and environmentally damaging. Petrochemical surfactants, alcoholic solvents, and ammonium hydroxide, which are commonly used, each have their own associated environmental problems. Demand is growing to find new, more sustainable ways, to synthesise spherical silica. Bioinspired and biomimetic silica, produced using knowledge learned from natural silica production methods such as biomineralisation, is an ever-growing field of research, that provides a possible route to more sustainable industrial silica production. Biomolecules can be used to shape and form spherical silica instead of petrochemical surfactants. Water-based chemistries can be used instead of alcohol solvents and ammonium hydroxide. This review establishes the parallels between the natural silica biomineralisation process and Stöber processes and focuses on the physicochemical properties necessary for biomolecules to synthesise spherical silica. Recent biomolecule-based syntheses are highlighted, and an outlook is given on further developments in the field.