Structure of monolayers

The inner structure of monolayers and bilayers, the liquid/gel transition, tilt transitions, mixed layers, etc. 

THE EFFECT OF IONIC REPULSION AMONG HYDROPHILIC GROUPS ON THE AGGREGATION STRUCTURE OF MONOLAYER... 

EFFECT OF POLYCATION IN SUBPHASE ON AGGREGATION STRUCTURE OF MONOLAYER OF ANIONIC AMPHIPHILE... 

The aggregation structure of monolayer during a compressing process at TSp below and above Tm. 

Y. Gamo, A. Nagashima, M. Wakabayashi, M. Terai, C. Oshima, Atomic structure of monolayer graphite formed on Ni(lll), Surface Science, 374 (1997) 61-64. 

Brett etal. [103] have studied selfassembling of 1-decanethiol at the fixed positive potentials of pc-Au electrode in chronoamperometry and quartz crystal microgravimetry. The obtained layers appeared to have improved quality and were produced faster than in the open-circuit deposition. The factors possibly influencing the fine structure of monolayers observed in voltammetric reductive desorption and oxidative redeposition of long-chain alka-nethiolates, for example, hexadecanethiol (HT) and octadecanethiol on smooth Au electrodes have been discussed [104]. It has been shown that the local order of adlayer has a role to play in the formation of that fine structure. 

We shall review the surface structures of monolayers of various homologues of organic compounds, the paraffins, the phthalocyanines, a few aromatic systems and amino acids that have been determined during recent investigations. 

Position of Metal Ions in Monolayer Lattice. The surface potential is an important parameter for studying the ionic structure of monolayers, including the position of metal ions in the monolayer lattice. The interaction of cations with anionic groups in a monolayer results in a formation of ionic dipoles which influence the surface potential. If the polarity of the ionic dipole is in the same direction as that of the rest of the molecule, the surface potential of the monolayer increases if the polarities are opposite, the surface potential decreases. It is known (21, 41, 46)... 

The last decade has seen the introduction of several new characterisation techniques which have been of major assistance in understanding the structure of monolayers at a molecular level. The most important of these has been the use of synchrotron radiation to obtain diffraction patterns from films at the air/water surface. In principle it would always have been possible to use X-rays for this purpose but the high intensity and highly monochromatic nature of the radiation from a synchrotron source has made this technique far easier to use. A selection of recent papers based on this technique is given [79-88], not all of which refer to simple fatty acids. The information available from such experiments is of two distinct kinds, though, in several studies, both kinds of information have been obtained. 

Unfortunately, while insoluble monolayers at the A/W interface have been extensively studies as models for interfacial phenomena, there is virtually no information available concerning the detailed physical structure of these films. Historically, this lack of information concerning the molecular-level structure of monolayers at the A/W interface can be traced to the inability of most spectroscopic techniques to study a low surface area, flat water interface with sufficient sensitivity to produce spectra with reasonable signal-to-noise ratios. This situation is changing with the introduction of the modem spectroscopic methods mentioned above. Even here, however, the number of spectroscopic techniques with in-situ sensitivity at the A/W interface is not large. Table II lists the methods that have been recently utilized to study the A/W interface in-situ. 

R. Aveyard, J. H. Clint, D. Nees, and V. N. Paunov, Compression and structure of monolayers of charged latex particles at air/water and Octane/Water interfaces, Langmuir 16, 1969-1979 (2000). 

As for Raman spectroscopy one may expect resonance Raman effect and/or surface-enhanced Raman scattering (SERS). By using these effects, the Raman spectrum of a monolayer film may be enhanced by 103-106. Resonance Raman spectroscopy is useful for exploring the electronic structure of monolayers with a chromophore and SERS technique is applied to study structure, orientation, and interactions of monolayers on a silver or gold surface. 

Recently, the investigation of monolayer models of biological membranes by neutron reflectometry has received some attention. For example, the changes in the structure of monolayers of dimyristoylphosphatidylglycerol (DMPG) and dimyristoylphosphatidylcholine (DMPC), which accompany the transition from an expanded to a condensed state, were reported by Bayerl et al. (1990). Monolayers composed of a mixture of perdeuterated DMPC and DMPG in the ratio 7 3 were deposited on D2O and ACMW subphases to... 

I. Low Temperature Structure of Monolayer and Bilayer Films, J. Chem. Phys. 92 (1990) 3858-3866 II. Monolayer Melting, ibid, 92 (1990) 3867-3873. 

In a study of the structure of monolayer films of carbon dioxide on graphite, Morishige [86] observed that carbon dioxide does not wet the graphite surface at temperatures below 104 K. It is likely that the electrostatic quadrupole inter-... 

Several new techniques have been developed by which it is possible to establish the boundaries between monolayer phases and the nature of the transitions between them. Other approaches have begun to provide direct information about the microscopic structures of monolayer phases. In this section, we will briefly describe these methods and their application to Langmuir monolayers. 

There are several important methods for determining the structure of monolayers that can be employed only when the substrate is solid. For example, LB films can be studied by electron diffraction, a technique... 

Harkin s (1952) monolayer phase description Structure of monolayer phases relation to three-dimensional states... 

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