Regensburg 2002 – wissenschaftliches Programm
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O: Oberflächenphysik
O 32: Adsorption an Oberfl
ächen (IV)
O 32.13: Vortrag
Donnerstag, 14. März 2002, 18:30–18:45, H43
Adsorption and desorption of D2O on SAMs of controlled wettability — •Yongjie Yang, Michael Zharnikov, and Michael Grunze — Angewandte Physikalische Chemie,Universität Heidelberg, D-69120 Heidelberg
Adsorption and desorption of thin overlayers of condensed D2O ice on self-assembled monolayers (SAMs) has been investigated. Mixed SAMs of HS(CH2)11OH and HS(CH2)11CH3 on gold with controlled wettability were used as model surfaces and characterized by contact angle measurements and infrared reflection-absorption spectroscopy (IRRAS). The D2O overlayers were adsorbed on the SAM substrates in ultrahigh vacuum at 100 K and investigated by temperature-programmed desorption, X-ray photoelectron spectroscopy and work function measurements. Adsorption and desorption kinetics as well as sticking coefficient and desorption energy were derived from the results. At low coverages, sticking coefficient decreases at going from a hydrophilic surface (-OH terminated SAMs) to a hydrophobic one (-CH3 terminated SAMs); but at high coverages (multi-layer region) the values of the sticking coefficient for different surfaces are quite close. The relationship between the wettability and the adsorption and desorption kinetics are discussed. Morphological transformation of the condensed D2O overlayers at going from a hydrophilic surface to a hydrophobic one were examined.