Amino-terminated organic monolayers on hydrogen-terminated silicon surfaces

A new approach has been developed to prepare amino-terminated monolayers on hydrogen-terminated silicon surfaces. This two-step procedure is the first method that provides direct control over the surface density of the amino groups. First, a mixed monolayer of a protected omega -amino-1-alkene and a nonfunctional 1-alkene is prepared on a H-terminated Si surface, using either phthalimide or acetamide as NH2-protecting groups. Subsequent removal of the protective groups generates the covalently attached NH2-terininated monolayer, as evidenced from water contact angle measurements, IR spectroscopy, and X-ray photoelectron spectroscopy. Both protecting groups have their own advantages: use of the phthalimide moiety is synthetically very convenient; the relatively small acetamide moiety can be used to prepare monolayers with high densities (> 50%) of amine groups. The reactivity of the amine groups has been confirmed by further modification of the monolayers.