aminopropyltriethoxysilane

3-aminopropyltriethoxysilane (APTES) is an organosilane coupling agent used to introduce primary amine groups onto surfaces. Its chemical formula is C9H23NO3Si. The molecule features a silicon atom bonded to three ethoxy groups and to a 3-aminopropyl group, enabling covalent attachment to hydroxylated surfaces such as silica, glass, or aluminum oxide while presenting an amine terminus for further functionalization.

In moisture, APTES hydrolyzes to silanols and can undergo condensation to form siloxane networks, enabling covalent bonding to substrates and to other silanes. The hydrolysis rate is influenced by pH, solvent, and impurities. Because it reacts with water, it is typically handled under dry or moisture-controlled conditions during surface treatment, and it is commonly used in combination with solvents that moderate its reactivity.

Common uses include surface modification of glass and silica materials, fabrication of functionalized sensors and biosensors, immobilization of proteins and nucleic acids, preparation of functional coatings, and as a primer in adhesives and polymer composites to enhance interfacial bonding. It is often applied to hydroxylated surfaces to provide an amine-functional handle for subsequent coupling reactions.

Safety and handling: APTES is an irritant and can cause skin, eye, and respiratory irritation. It should be handled with appropriate protective equipment in a well-ventilated area, preferably a fume hood. Avoid contact with moisture, and store the material in a dry, tightly closed container away from incompatible substances. Hydrolysis products may generate volatile byproducts such as ethanol.