Direct visualization of monolayers at the air-water interface by Brewster angle microscopy

Hoenig, D.; Moebius, D.

doi:10.1021/j100165a003

Cited by 901 publications

(503 citation statements)

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“…MgF2 layer was chosen to be 50 nm to achieve high sensitivity according to equation (20 Bilayers of synthetic lecithins exhibit different phases due to their long-range Organization in the bilayer. The most common are the liquid-like (La), the corrugated gel-phase (P^) (ripple phase) and the homogeneously tilted gel-phase (L^).…”

Section: Firstly We Studied the Ric Pattern Of A Spherical Vesicle Imentioning

confidence: 99%

Imaging optical thicknesses and separation distances of phospholipid vesicles at solid surfaces

1993

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We present the application of reflection interference contrast microscopy (RICM) (1) to map the optical density of supported bilayers and vesicles and (2) to image the contact profile of phospholipid vesicles at surfaces. The resolution in the surface profile is 0.2 μm laterally and 1 nm out of plane. The optical thickness of the membrane can be determined with 0.2 nm accuracy. We outline the theoretical basis of RICM and derive the interference intensities of adhering vesicles from first principles. An analytical expression for the decaying contrast of the intrference fringes is given. The contact contour of vesicles is determined for various substrates. We further demonstrate that deposition of a magnesium fluoride layer on the glass substrate enhances the contrast and allows the optical density of adsorbed membranes to be imaged. By contrast variation of the buffer solution, the layer thicknesses and the indices of refraction can be measured. The novel method was applied to image lipid domains of different chain lengths in a substrate supported monolayer

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Section: Firstly We Studied the Ric Pattern Of A Spherical Vesicle Imentioning

confidence: 99%

Imaging optical thicknesses and separation distances of phospholipid vesicles at solid surfaces

1993

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“…22 We used Brewster angle microscopy 23 (BAM) to characterize monolayer morphology during compressions. Formation of small (ca.…”

Section: Introductionmentioning

confidence: 99%

Structure and Lateral Electron Hopping in Osmium-tris-4,7-diphenylphenanthroline Perchlorate Monolayers at the Air/Water Interface

et al. 1999

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Osmium tris-diphenylphenanthroline perchlorate (Os(DPP) 3 ) can be spread at the air/water interface where it forms solid monolayer films. Brewster angle microscopy revealed that these films consist of irregular ca. 100 to 1000 µm diameter 2D aggregates which coalesce upon compression to form continuous films. Grazing incidence X-ray diffraction data showed that the structure of the aggregates is independent of the degree of monolayer compression and features a 2D lattice of hexagonally close-packed Os(DPP) 3 centers with Os-Os distances of 12.57 Å. The latter is 4 to 24% shorter than the Ru-Ru distances found in the 3D monoclinic crystal of an isostructural Ru (DPP) 3 . Two dimensional electrochemical measurements carried out with line microelectrodes at the air/water interface were used to study kinetics of the lateral electron transport in these Langmuir monolayers. Electron transport involves electron hopping on the 2D lattice of the osmium sites where the individual electron transfer steps between Os II (DPP) 3 and Os III (DPP) 3 take place with the rate constant k 1 ) 4.7 × 10 8 s -1 . Percolation theory was used to account for the observed increase of the electron hopping rates during monolayer compression on the water surface resulting in an increase of the extent of connectivity and thus electroactivity of the initially formed 2D Os(DPP) 3 aggregates. Percolation theory also accounts well for the dependence of the electron hopping rates on the composition of fully compressed Os-(DPP) 3 /Ru(DPP) 3 monolayers in which the ruthenium species were used to homogeneously dilute the Os-(DPP) 3 sites. In contrast, in Os(DPP) 3 /octadecanol monolayers, macroscopic self-segregation of the two components was inferred from a larger positive shift of the apparent percolation threshold in the lateral electron hopping.

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“…Brewster angle microscopy (BAM) was developed as a powerful method for optical characterization of monolayers at the air/water interface (14,15). BAM, as a non perturbing technique for the microscopic characterization of the monolayer provides information about the homogeneity of the film, existence and formation of domains, phase transition and adsorption of material from the aqueous phase.…”

Section: Introductionmentioning

confidence: 99%

Physicochemical Characterization of Natural andex-SituReconstructed Sea-Surface Microlayers

Gašparović

Kozarac

Saliot

et al. 1998

Journal of Colloid and Interface Science

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Running title: Sea-surface microlayers 2 Chemical composition and physico-chemical characteristics of natural and ex-situ reconstructed sea surface microlayer samples were studied using a complex methodological approach. Surface microlayer samples and the underlying seawater were collected in different seasons and different weather conditions in the northern most part of the Adriatic sea. The techniques used were thin layer chromatography with flame ionization detection for lipid classes analysis, electrochemical characterization of adsorbable organic substances using the ONP probe and monolayer techniques for surface pressure () and surface potential ( V) measurements, as well as Brewster angle microscopy.Our results indicated higher enrichment of organic matter for the microlayer sample collected in the warm period of the year (summer). This was reflected in the high surface activity of the present organic substances, and formation of a more condensed layer than for the other two samples collected in the spring. Of the two spring samples, the one sampled on a sunny day was reacher in surface active organic material. We concluded that the most important source of surface active substances is the insitu production of organic susbtances by the present plankton and bacteria, promoted by sunlight, while antrophogenic input comprises a smaller part of the present organic matter, around 10 % for all samples.Key Words: sea-surface microlayer; lipid analysis; o-nitrophenol; surface active organic substances; voltammetry; monolayer studies; Brewster angle microscopy; northern Adriatic. 3 INTRODUCTIONSea surface microlayer is an important boundary, as an area of exchange of matter and energy, that either affects or is affected by global change (1, 2). Sea surface layer is generally enriched in organic substances, particularly those which are surface active, metal ions, bacteria and other microorganisms, relative to subsurface water (3-5). Organic substances found in the microlayer originate from the in-situ production or from different sources and have been brought there by different transport mechanisms from the seawater bulk, atmosphere or land. Adsorbed organic substances change the physical and optical properties, depending on the nature of organics, i.e. the nature of polar groups, architecture of the hydrophobic chain, and ionic strength, pH and temperature.Although the physical and chemical properties of the sea-surface microlayer have been studied extensively, there is still lack of knowledge about the physico-chemical processes governing the formation and properties of the surface microlayer.Electrochemical methods have been widely used for the investigation of surface active substances (SAS) in different waters (6 -9). These methods are based on the principle that organic substances adsorbed on the electrode surface influence the mass and charge transport across such a modified phase boundary. The recently developed electrochemical method using the o-nitrophenol (ONP) probe as a convenient tool for rough char...

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Direct visualization of monolayers at the air-water interface by Brewster angle microscopy

Cited by 901 publications

References 0 publications

Imaging optical thicknesses and separation distances of phospholipid vesicles at solid surfaces

Imaging optical thicknesses and separation distances of phospholipid vesicles at solid surfaces

Structure and Lateral Electron Hopping in Osmium-tris-4,7-diphenylphenanthroline Perchlorate Monolayers at the Air/Water Interface

Physicochemical Characterization of Natural andex-SituReconstructed Sea-Surface Microlayers

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