Dresden 2006 – scientific programme
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O: Oberflächenphysik
O 38: Adsorption V
O 38.2: Talk
Thursday, March 30, 2006, 15:15–15:30, TRE Phys
Toward direct structure determination of adsorbed molecules: D and L cysteine on Cu(17 11 9)s — •Richard Schillinger1,2 und Thomas Greber1 — 1Universiät Zürich, Winterthurerstrasse 190, CH 8057 Zürich, Schweiz — 2Paul Scherrer Institut, CH 5232 Villigen PSI, Schweiz
Adsorption of biomolecules on metal surfaces finds an increasing number of applications from biocompatibility to chemical sensing.
The Cu(17 11 9) is a chiral vicinal (111) surface with 14 atoms in the unit cell. Upon adsorption of cysteine already in the monolayer (coverage 4 to 5 molecules per unit cell)find we hints for a change in conformation or ordering of the molecules from core level shifts and from angle scanned X-ray photoelectron diffraction (XPD). Further on, the XPD data point toward a pairing of the molecules in the (17 11 9) unit cell. This finding is in contrast to the situation on the also chiral Au(17 11 9)s surface, where we observe ordered single orientation adsorption with a different conformation for the D and L enantiomer. In the monolayer cysteine takes the neutral acidic (SCH2CH(NH2)-COOH) state. Upon multilayer formation the molecule takes the zwiterionic (HSCH2CH(NH3+)-COO-) state, identified by appearence of the respective components in the C1s, N1s, S2p, and O1s core level spectra. The experiments were performed on enantiopure systems i.e. only D or L cysteine was evaporated at one time.