Interactions of Alcohols with Hydroxyl- and Methyl-Terminated Self-Assembled Monolayer Surfaces Studied by Temperature-Programmed Desorption

Abstract

The interactions of low-molecular-weight n-alcohols (n-CxH2x+1OH for x = 1−6) with 11-mercaptoundecanol (HO(CH2)11SH) or octadecyl mercaptan (CH3(CH2)17SH) adsorbed onto a nickel(111) single-crystal surface were studied by temperature-programmed desorption (TPD). Angle-dependent X-ray photoelectron spectroscopy (ADXPS) was used to characterize the adsorption of HO(CH2)11SH and CH3(CH2)17SH molecules to determine their arrangements on the nickel(111) surface. The TPD spectra for the desorption of alcohols from the hydroxyl-terminated and the methyl-terminated self-assembled monolayer surfaces at various alcohol fluences were analyzed by the threshold TPD method (TTPD) to determine their desorption energies as a function of the alcohol fluence. The TTPD-calculated alcohol desorption energies from the hydroxyl-terminated surface increased from 10 to 20 kJ mol-1 for the lowest fluences to 40−60 kJ mol-1 for the highest fluences; from the methyl-terminated 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.