Depth distribution of irradiation-induced cross-linking in aromatic self-assembled monolayers.
Pristine and strongly irradiated self-assembled monolayers of [1,1':4',1' '-terphenyl]-4,4' '-dimethanethiol (TPDMT) on Au have been characterized by near-edge X-ray absorption fine structure spectroscopy using partial electron yield acquisition mode. The TPDMT films were found to be extremely stable toward electron irradiation, which is explained by cross-linking between the aromatic backbones. In addition, we assume that a large delocalization and a strong relaxation of the initial electronic excitations in the densely packed film contributed to the film stability. The data analysis implies an inhomogeneous distribution of the irradiation-induced dehydrogenation and cross-linking of the terphenyl moieties in the TPDMT film, being most pronounced close to the film-ambient interface. The inhomogeneity was explained by quenching of the electronically excited C-H states via dipole-dipole interaction with the states' image at the metal surface, which has a reduced probability with increasing separation from the metal surface. Generally, the results suggest the importance of relaxation processes for the response of self-assembled monolayers to ionizing radiation.
Angewandte Physikalische Chemie, Universität Heidelberg, Im Neuenheimer Feld 253, 69120 Heidelberg, Germany.
Y
Y
Tai
A
A
Shaporenko
W
W
Eck
M
M
Grunze
M
M
Zharnikov
D003432:Cross-Linking Reagents / Q000737:chemistry* / Q000528:radiation effects*; D004583:Electrons; D006046:Gold / Q000737:chemistry; D006841:Hydrocarbons, Aromatic / Q000737:chemistry* / Q000528:radiation effects*; D008567:Membranes, Artificial; D015394:Molecular Structure; D012680:Sensitivity and Specificity; D013057:Spectrum Analysis; D013438:Sulfhydryl Compounds / Q000737:chemistry* / Q000528:radiation effects*; D013499:Surface Properties; D013730:Terphenyl Compounds / Q000737:chemistry* / Q000528:radiation effects*; D014965:X-Rays
C510727:(1,1'-4',1''-terphenyl)-4,4''-dimethanethiol; D003432:Cross-Linking Reagents; D006841:Hydrocarbons, Aromatic; D008567:Membranes, Artificial; D013438:Sulfhydryl Compounds; D013730:Terphenyl Compounds; D006046:Gold