Near-edge x-ray-absorption fine structure (NEXAFS) spectroscopy was adopted to probe the unoccupied electronic states of anchored onto an organized assembly of 11-amino-1-undecane thiol on Au(111). The polarization dependence of the intensity of resonance associated with network revealed the self-assembled monolayer (SAM) system to be oriented with an average molecular tilt angle of 57° with respect to the surface normal. Invoking the absence of solid-state band dispersion effects and in comparison to solid and /or 1-ML /Au(111), the electronic structure of the resulting assembly was found dominated by spectral position shift and linewidth and intensity changes of the lowest unoccupied molecular orbital (LUMO), , and orbitals. The latter implied hybridization between N of group of thiolate SAM and levels of , resulting in a nucleophilic addition with a change in the symmetry of from to in the SAM. Occurrence of a new feature at 285.3 eV in the NEXAFS spectrum, assigned previously to graphitic LUMO, signified the formation of aggregated clusters, of monomer. Low tunneling current scanning tunneling microscopy confirmed them to be spherical and stable aggregates with .
Polarized near-edge x-ray-absorption fine structure spectroscopy of -functionalized 11-amino-1-undecane thiol self-assembled monolayer: Molecular orientation and Evidence for aggregation
Archita Patnaik, Koji K. Okudaira, Satoshi Kera, Hiroyuki Setoyama, Kazuhiko Mase, Nobuo Ueno; Polarized near-edge x-ray-absorption fine structure spectroscopy of -functionalized 11-amino-1-undecane thiol self-assembled monolayer: Molecular orientation and Evidence for aggregation. J. Chem. Phys. 15 April 2005; 122 (15): 154703. https://doi.org/10.1063/1.1880952
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