We compare two different strategies for fabricating self-assembled monolayers (SAMs) exhibiting a thiol-terminated organic surface, which recently has attracted considerable interest with regard to the binding of metal, and in particular gold particles, to these organic surfaces. Results obtained by IR spectroscopy and scanning tunneling microscopy (STM) reveal that the straightforward approach, namely, using the corresponding organodithiols, typically leads to the formation of disordered, ill-defined surfaces. We demonstrate that high-quality organothiolate adlayers exhibiting an SH-terminated surface can be prepared using dithiols where one of the thiol groups is protected by a thioester group. After formation of the organothiolate adlayer, the protecting group can be removed by immersion into NaOH solution. IR spectra recorded for the deprotected organothiolate adlayer reveal the presence of a highly oriented organothiolate adlayer.

The adsorption of ethylbenzene and styrene on well ordered epitaxial iron oxide model catalyst films with different stoichiometries was investigated using near edge X-ray absorption fine structure spectroscopy (NEXAFS). On the iron-terminated Fe3O4(111) and α-Fe2O3(0001) surfaces a chemisorption of ethylbenzene and styrene is observed whi ch initially occurs on the iron sites via the π-electron system of the phenyl ring. This forces the molecules into an almost flat lying configuration (η 6 like ring adsorption geometry). In the case of ethylbenzene this adsorption complex is supposed to lead to an activation of the C-H bonds thus facilitating the dehydrogenation to styrene. The tilt angle of the aromatic ring systems increase to about 40° when approaching monolayer saturation. In contrast, the interaction with the oxygen-terminated FeO(111) surface is weak and of the physisorption type. The adsorbate-adsorbate interaction dominates and causes a tilted adsorption of the molecules from the beginning.

Articles you may be interested inInvestigating the molecule-substrate interaction of prototypic tetrapyrrole compounds: Adsorption and selfmetalation of porphine on Cu(111) J. Chem. Phys. 138, 154710 (2013); 10.1063/1.4800771 Adsorption geometry, conformation, and electronic structure of 2H-octaethylporphyrin on Ag(111) and Fe metalation in ultra high vacuumThe adsorption of benzene, naphthalene, and anthracene on the TiO 2 (110) surface has been investigated using near edge x-ray absorption spectroscopy ͑NEXAFS͒, x-ray photoelectron spectroscopy, and thermal programmed desorption. For all three adsorbates a planar adsorption geometry is found. In contrast to the bonding of benzene and larger acenes to metal surfaces, we find that the interaction is dominated by electrostatic forces between the adsorbed molecules and the TiO 2 (110) substrate. The fact that the average tilt angle between molecular and surface plane as determined by NEXAFS is substantially different from zero indicates the presence of defect species.

The adsorption of styrene on (111)-oriented thin layers of FeO and Fe 3 O 4 epitaxially grown on Pt(111) singlecrystal surfaces has been investigated using near-edge X-ray absorption fine structure (NEXAFS) spectroscopy and X-ray photoelectron spectroscopy (XPS). High-resolution gas-phase measurements were recorded, and precise ab initio electronic structure calculations were performed in order to aid the assignment of the NEXAFS resonances. Whereas on Fe 3 O 4 (magnetite), styrene forms a chemisorbed monolayer that is stable up to room temperature, on FeO (wustite), a significantly more weakly bound (physisorbed) species is observed that is stable only for temperatures below 200 K. A planar adsorption geometry is observed in the case of styrene on Fe 3 O 4 in the low-coverage regime (Θ < 0.5 ML); for higher coverages on the same surface and on FeO, the average tilt angle between the phenyl plane and the surface plane amounts to about 45°.

The deposition and subsequent decomposition of a cyclopentadienyl-allyl-palladium precursor on a Pd(111) single crystal was investigated by a combination of X-ray photoelectron spectroscopy (XPS) and near edge X-ray absorption fine structure (NEXAFS) spectroscopy. Because the precursor decomposes readily on metal surfaces, a deposition system with its inner surfaces completely covered by chemically inert materials such as glass or Teflon was used to keep the precursor molecules intact prior to the deposition process. Upon adsorption on the palladium substrate surface, the precursor molecules are chemically modified even at temperatures as low as 170 K. At higher temperatures, the precursor decomposes, the oxidation state of the palladium changes from +2 to 0, and the ligands remain adsorbed at the palladium surface. Attempts to remove the hydrocarbon ligands by etching with molecular hydrogen were not successful.