tetraethoxysilane

Tetraethoxysilane, commonly abbreviated TEOS, is a silicon alkoxide with the formula Si(OEt)4. It features a central silicon atom tetrahedrally bonded to four ethoxy groups and is a volatile, colorless liquid used as a silica precursor in various chemical and materials-processing applications.

TEOS is typically produced by the alcoholysis of silicon tetrachloride with ethanol, yielding Si(OEt)4 and hydrochloric acid. Alternative methods include transesterification routes. Because TEOS readily hydrolyzes in the presence of moisture, it is handled under dry conditions and stored in moisture-controlled environments to minimize premature hydrolysis.

In air or water, TEOS undergoes hydrolysis to form silanol groups (Si–OH) and ethanol. The silanols subsequently undergo condensation reactions to form siloxane (Si–O–Si) linkages, leading to silica networks. The rate of hydrolysis and condensation can be adjusted with catalysts, pH, and water content, enabling control over the structure of the resulting silica.

Applications of TEOS arise mainly from its role as a silica source in sol–gel chemistry. It is used to prepare silica coatings, thin films, monoliths, and porous or dense silica materials. TEOS-based gels and sol–gel-derived materials find use in protective and optical coatings, ceramic precursors, and inorganic–organic composite systems.

Safety and handling: TEOS is a flammable organic compound and an irritant. It can release ethanol upon hydrolysis and should be handled with appropriate ventilation, sourcing from dry containers, and away from incompatible materials.