The quartz crystal microbalance (QCM) has been employed extensively fo
r measurement of mass changes at metal surface while the metal coated
electrode is immersed in a liquid. We report the real time in-situ ads
orption kinetic trends of alkanethiol CH3(CH2)(n-1)SH (n = 8, 12, 16)
monolayers with different chain lengths and solvents using QCM. Regard
ing 1-octanethiol monolayer formation on gold surface, we could identi
fy the two distinct monolayer formation steps in hexane and ethanol so
lutions. The adsorption process of alkanethiols is characterized by tw
o distinct steps. In the kinetically controlled initial monolayer form
ation step, the adsorption rate of short chain alkanethiols is faster
than that of long chain alkanethiols. The second step is a thermodynam
ically controlled ordering and packing process. In case of short chain
alkanethiols, these two separated adsorption steps were clearly obser
ved, but in the case of long chain alkanethiols (over 10 carbon number
s) only one step of monolayer formation was observed. (C) 1998 Elsevie
r Science S.A. All rights reserved.