Interactions of alcohols with hydroxyl- and methyl-terminated self-assembled monolayer surfaces studied by temperature-programmed desorption

The interactions of low-molecular-weight n-alcohols (n-CxH2x+1OH for x = 1- 6) with 11-mercaptoundecanol (HO(CH2)(11)SH) or octadecyl mercaptan (CH3(CH 2)(17)SH) adsorbed onto a nickel(lll) single-crystal surface were studied b y temperature-programmed desorption (TPD). Angle-dependent X-ray photoelect ron spectroscopy (ADXPS) was used to characterize the adsorption of HO(CH2) (11)SH and CH3(CH2)(17)SH molecules to determine their arrangements on the nickel(111) surface. The TPD spectra for the desorption of alcohols from th e hydroxyl-terminated and the methyl-terminated self-assembled monolayer su rfaces at various alcohol fluences were analyzed by the threshold TPD metho d (TTPD) to determine their desorption energies as a function of the alcoho l fluence. The TTPD-calculated alcohol desorption energies from the hydroxy l-terminated surface increased from 10 to 20 kJ mol(-1) for the lowest flue nces to 40-60 kJ mol(-1) for the highest fluences; from the methyl-terminat ed surface the desorption energy increased from 10 to 25 kJ mol(-1) for the lowest fluences to 45-55 kJ mol(-1) for the highest fluences.