3mercaptopropyltrimethoxysilane

3-mercaptopropyltrimethoxysilane, commonly abbreviated as MPTMS, is an organosilane coupling agent that provides a thiol (-SH) functionality at the end of a propyl chain attached to a silicon atom bearing three methoxy groups. Its chemical structure is (CH3O)3Si–(CH2)3–SH. In the presence of moisture, the methoxy groups hydrolyze to silanols, which can condense with hydroxyl groups on surfaces such as silica, glass, or metal oxides to form covalent Si–O–Si linkages. This process yields thiol-terminated surfaces that can participate in further chemical modification.

Because of the thiol terminus, MPTMS is widely used to functionalize inorganic substrates for subsequent chemistry. It enables the formation of self-assembled monolayers on glass and silica-based materials, providing a convenient platform for immobilizing metal nanoparticles (notably gold and silver), biomolecules, or other reactive species through thiol, disulfide, or metal-thiol interactions. Applications include preparation of sensor surfaces, microfluidic device functionalization, and the creation of thiol-terminated interfaces for biosensing, catalysis, and surface-enhanced spectroscopy. It can also serve as a coupling step in preparing thiol-terminated stationary phases for affinity or chromatographic applications.

Handling and safety considerations reflect its silane and thiol character. MPTMS is moisture-sensitive and reacts with water to form methanol and silanols; it is typically stored in dry conditions under inert gas. It can be irritant to skin and eyes and may release flammable methanol upon hydrolysis, so appropriate handling, ventilation, and personal protective equipment are advised.