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 eit
her phthalimide or acetamide as NH2-protecting groups. Subsequent removal o
f the protective groups generates the covalently attached NH2-terininated m
onolayer, as evidenced from water contact angle measurements, IR spectrosco
py, and X-ray photoelectron spectroscopy. Both protecting groups have their
own advantages: use of the phthalimide moiety is synthetically very conven
ient; the relatively small acetamide moiety can be used to prepare monolaye
rs with high densities (> 50%) of amine groups. The reactivity of the amine
groups has been confirmed by further modification of the monolayers.