Comparison and Contrast
Analysis of Adsorption Geometries
of Phenylalanine versus Tyrosine on Ge(100): Effect of Nucleophilic
Group on the Surface
- Publication date
- Publisher
Abstract
The discrepancy of geometric configuration between phenylalanine
and tyrosine adsorbed on Ge(100) surfaces was investigated using scanning
tunneling microscopy (STM) in conjunction with density functional
theory (DFT) calculations and core-level photoemission spectroscopy
(CLPES). The study focused on the role of nucleophilic group (hydroxyl
group) on phenyl ring of tyrosine, and we elucidated the difference
of the adsorption geometry between phenylalanine and tyrosine on Ge(100)
surfaces. We first confirmed that the “O–H dissociated–N
dative bonded structure” was the most favorable structure in
both molecules at low coverage by results of CLPES and DFT calculations.
Geometric differences for the adsorption configurations between phenylalanine
and tyrosine were observed: the phenyl ring of phenylalanine was aligned
axially with respect to the Ge(100) surface, whereas that of tyrosine
was tilted, as determined by DFT calculations. In sequence, we found
out the results of STM images to confirm DFT results. We determined
the different geometric configurations are attributed to the nucleophilic
hydroxyl group of tyrosine, which creates an uneven charge distribution