Organic Monolayer Films Research Articles

Self-Assembled Organic Monolayer Films on Underpotentially Deposited Metal Layers

ABSTRACTThis paper describes a new family of organized molecular assemblies that are produced by the spontaneous adsorption of alkanethiols onto gold surfaces that have been modified by the underpotential deposition of copper or silver. The system has the flexibility associated with the formation of self-assembled monolayers by the adsorption of thiols onto gold with the advantage of improved stability. The use of these systems as modified electrodes is also addressed.

Mechanical relaxation of organic monolayer films measured by force microscopy.

Using the newly developed interfacial-force microscope, we present results for the first measurements of the mechanical relaxation of a Au supported, self-assembled monolayer film interacting with a microscopic tungsten tip. For a methyl-terminated n-alkanethiol film, we observe negligible adhesive film-tip interaction and complete passivation of tip-substrate bonding. The mechanical behavior of the film itself shows a time-dependent, elastic response.

Monolayers of 11-trichlorosilylundecyl thioacetate: A system that promotes adhesion between silicon dioxide and evaporated gold

The use of sulfur-containing organic monolayer films improves adhesion between gold and silicon dioxide. The structures of these monolayers were analyzed using contact angle, ellipsometry, and XPS. The zone of adhesive failure was at or near the gold-monolayer interface.

Infrared Spectra of Organic Monolayers on Mica

A method is described for obtaining infrared spectra of an organic monolayer film on muscovite mica. This task is normally difficult because mica is not metallic, and it has biaxial optical properties and produces large interference fringes when analyzed in transmission or reflection because of reflections off the front and back of a sheet. The method involves the transmission of parallel-polarized light, incident at the Brewster's angle, through a mica sheet that is oriented along one of its principal optical directions.

Ionic recognition and selective response in self-assembling monolayer membranes on electrodes

According to the invention organic monolayer films are applied to an electrically conductive substrate, resulting in an electrode which can be used in electrochemical processes. The said film serves as ultrathin membrane and allows certain selected species to approach the substrate and be detected. The film comprises active species which are selective towards specific species contained in mixture with others and a blocking surface sealing component. It is also possible to use one compound serving both purposes. The components of the film are attached to the substrate by a variety of means: adsorption, chemisorption, electro-chemical deposition.

Observation of structural change in organic monolayer film by penning ionization electron spectroscopy: Fe-phthalocyanine on graphite

Structures of Fe-phthalocyanine adsorbed on a graphite substrate (cleavage plane) were studied by Penning ionization electron spectroscopy (PIES). The structural change, disordered layer → closely packed monolayer → island, was observed upon heating the film deposited on the substrate held at 123 K. For the monolayer and island structures, molecules were found to be oriented flat to the substrate. It was concluded that PIES was a useful technique to probe the change in molecular arrangement during order-disorder transformation in monolayer films.

Observation of structural change in organic monolayer film by penning ionization electron spectroscopy: Fe-phthalocyanine on graphite

Observation of structural change in organic monolayer film by penning ionization electron spectroscopy: Fe-phthalocyanine on graphite

Observation of structural change in organic monolayer film by penning ionization electron spectroscopy: fe-phthalocyanine on graphite

Observation of structural change in organic monolayer film by penning ionization electron spectroscopy: fe-phthalocyanine on graphite

On the formation and structure of self-assembling monolayers: II. A comparative study of Langmuir—Blodgett and adsorbed films using ellipsometry and IR reflection—absorption spectroscopy

Ellipsometry and infrared reflection-absorption (RA) spectroscopy on aluminium mirrors provide independent evidence confirming the basic structural similarity of Langmuir-Blodgett (LB) and adsorbed monolayers. The systems presently analyzed comprise a homologous series of saturated fatty acids, a saturated long chain trichlorosilane, a vinylic long chain acid, and a vinylic long chain trichlorosilane. Conclusive evidence is obtained from RA spectra of adsorbed monolayers of a long chain acid and a long chain silane for the independence of the chain orientation in such monolayers on the specific mode of film-to-surface binding. The orientation of the chains is found to be essentially perpendicular, but not perfect. The unique value of RA spectroscopy in the detection of order-disorder transformations accompanying interactions of a highly oriented monolayer with physical or chemical external agents is demonstrated. Covalently bonded silane monolayers are shown to be perfectly stable under conditions causing a major deterioration of the structure of adsorbed fatty acid films. The adsorption of fatty acids on aluminium is found to involve physical forces only. Under the conditions of the present experiments ellipsometry is found to be of limited value as a routine analytical tool in the characterization of organic monolayer films. This has to do with the hypersensitivity of this technique to a large number of factors, part of which are difficult to control and reproduce.